Merge git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus

[deliverable/linux.git] / arch / sparc / mm / sun4c.c

/* sun4c.c: Doing in software what should be done in hardware.
 *
 * Copyright (C) 1996 David S. Miller (davem@davemloft.net)
 * Copyright (C) 1996 Eddie C. Dost (ecd@skynet.be)
 * Copyright (C) 1996 Andrew Tridgell (Andrew.Tridgell@anu.edu.au)
 * Copyright (C) 1997-2000 Anton Blanchard (anton@samba.org)
 * Copyright (C) 1998 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
 */

#define NR_TASK_BUCKETS 512

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/highmem.h>
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/scatterlist.h>

#include <asm/sections.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/vaddrs.h>
#include <asm/idprom.h>
#include <asm/machines.h>
#include <asm/memreg.h>
#include <asm/processor.h>
#include <asm/auxio.h>
#include <asm/io.h>
#include <asm/oplib.h>
#include <asm/openprom.h>
#include <asm/mmu_context.h>
#include <asm/highmem.h>
#include <asm/btfixup.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>

/* Because of our dynamic kernel TLB miss strategy, and how
 * our DVMA mapping allocation works, you _MUST_:
 *
 * 1) Disable interrupts _and_ not touch any dynamic kernel
 *    memory while messing with kernel MMU state.  By
 *    dynamic memory I mean any object which is not in
 *    the kernel image itself or a thread_union (both of
 *    which are locked into the MMU).
 * 2) Disable interrupts while messing with user MMU state.
 */

extern int num_segmaps, num_contexts;

extern unsigned long page_kernel;

/* That's it, we prom_halt() on sun4c if the cache size is something other than 65536.
 * So let's save some cycles and just use that everywhere except for that bootup
 * sanity check.
 */
#define SUN4C_VAC_SIZE 65536

#define SUN4C_KERNEL_BUCKETS 32

/* Flushing the cache. */
struct sun4c_vac_props sun4c_vacinfo;
unsigned long sun4c_kernel_faults;

/* Invalidate every sun4c cache line tag. */
static void __init sun4c_flush_all(void)
{
        unsigned long begin, end;

        if (sun4c_vacinfo.on)
                panic("SUN4C: AIEEE, trying to invalidate vac while it is on.");

        /* Clear 'valid' bit in all cache line tags */
        begin = AC_CACHETAGS;
        end = (AC_CACHETAGS + SUN4C_VAC_SIZE);
        while (begin < end) {
                __asm__ __volatile__("sta %%g0, [%0] %1\n\t" : :
                                     "r" (begin), "i" (ASI_CONTROL));
                begin += sun4c_vacinfo.linesize;
        }
}

static void sun4c_flush_context_hw(void)
{
        unsigned long end = SUN4C_VAC_SIZE;

        __asm__ __volatile__(
                "1:     addcc   %0, -4096, %0\n\t"
                "       bne     1b\n\t"
                "        sta    %%g0, [%0] %2"
        : "=&r" (end)
        : "0" (end), "i" (ASI_HWFLUSHCONTEXT)
        : "cc");
}

/* Must be called minimally with IRQs disabled. */
static void sun4c_flush_segment_hw(unsigned long addr)
{
        if (sun4c_get_segmap(addr) != invalid_segment) {
                unsigned long vac_size = SUN4C_VAC_SIZE;

                __asm__ __volatile__(
                        "1:     addcc   %0, -4096, %0\n\t"
                        "       bne     1b\n\t"
                        "        sta    %%g0, [%2 + %0] %3"
                        : "=&r" (vac_size)
                        : "0" (vac_size), "r" (addr), "i" (ASI_HWFLUSHSEG)
                        : "cc");
        }
}

/* File local boot time fixups. */
BTFIXUPDEF_CALL(void, sun4c_flush_page, unsigned long)
BTFIXUPDEF_CALL(void, sun4c_flush_segment, unsigned long)
BTFIXUPDEF_CALL(void, sun4c_flush_context, void)

#define sun4c_flush_page(addr) BTFIXUP_CALL(sun4c_flush_page)(addr)
#define sun4c_flush_segment(addr) BTFIXUP_CALL(sun4c_flush_segment)(addr)
#define sun4c_flush_context() BTFIXUP_CALL(sun4c_flush_context)()

/* Must be called minimally with interrupts disabled. */
static void sun4c_flush_page_hw(unsigned long addr)
{
        addr &= PAGE_MASK;
        if ((int)sun4c_get_pte(addr) < 0)
                __asm__ __volatile__("sta %%g0, [%0] %1"
                                     : : "r" (addr), "i" (ASI_HWFLUSHPAGE));
}

/* Don't inline the software version as it eats too many cache lines if expanded. */
static void sun4c_flush_context_sw(void)
{
        unsigned long nbytes = SUN4C_VAC_SIZE;
        unsigned long lsize = sun4c_vacinfo.linesize;

        __asm__ __volatile__(
        "add    %2, %2, %%g1\n\t"
        "add    %2, %%g1, %%g2\n\t"
        "add    %2, %%g2, %%g3\n\t"
        "add    %2, %%g3, %%g4\n\t"
        "add    %2, %%g4, %%g5\n\t"
        "add    %2, %%g5, %%o4\n\t"
        "add    %2, %%o4, %%o5\n"
        "1:\n\t"
        "subcc  %0, %%o5, %0\n\t"
        "sta    %%g0, [%0] %3\n\t"
        "sta    %%g0, [%0 + %2] %3\n\t"
        "sta    %%g0, [%0 + %%g1] %3\n\t"
        "sta    %%g0, [%0 + %%g2] %3\n\t"
        "sta    %%g0, [%0 + %%g3] %3\n\t"
        "sta    %%g0, [%0 + %%g4] %3\n\t"
        "sta    %%g0, [%0 + %%g5] %3\n\t"
        "bg     1b\n\t"
        " sta   %%g0, [%1 + %%o4] %3\n"
        : "=&r" (nbytes)
        : "0" (nbytes), "r" (lsize), "i" (ASI_FLUSHCTX)
        : "g1", "g2", "g3", "g4", "g5", "o4", "o5", "cc");
}

/* Don't inline the software version as it eats too many cache lines if expanded. */
static void sun4c_flush_segment_sw(unsigned long addr)
{
        if (sun4c_get_segmap(addr) != invalid_segment) {
                unsigned long nbytes = SUN4C_VAC_SIZE;
                unsigned long lsize = sun4c_vacinfo.linesize;

                __asm__ __volatile__(
                "add    %2, %2, %%g1\n\t"
                "add    %2, %%g1, %%g2\n\t"
                "add    %2, %%g2, %%g3\n\t"
                "add    %2, %%g3, %%g4\n\t"
                "add    %2, %%g4, %%g5\n\t"
                "add    %2, %%g5, %%o4\n\t"
                "add    %2, %%o4, %%o5\n"
                "1:\n\t"
                "subcc  %1, %%o5, %1\n\t"
                "sta    %%g0, [%0] %6\n\t"
                "sta    %%g0, [%0 + %2] %6\n\t"
                "sta    %%g0, [%0 + %%g1] %6\n\t"
                "sta    %%g0, [%0 + %%g2] %6\n\t"
                "sta    %%g0, [%0 + %%g3] %6\n\t"
                "sta    %%g0, [%0 + %%g4] %6\n\t"
                "sta    %%g0, [%0 + %%g5] %6\n\t"
                "sta    %%g0, [%0 + %%o4] %6\n\t"
                "bg     1b\n\t"
                " add   %0, %%o5, %0\n"
                : "=&r" (addr), "=&r" (nbytes), "=&r" (lsize)
                : "0" (addr), "1" (nbytes), "2" (lsize),
                  "i" (ASI_FLUSHSEG)
                : "g1", "g2", "g3", "g4", "g5", "o4", "o5", "cc");
        }
}

/* Don't inline the software version as it eats too many cache lines if expanded. */
static void sun4c_flush_page_sw(unsigned long addr)
{
        addr &= PAGE_MASK;
        if ((sun4c_get_pte(addr) & (_SUN4C_PAGE_NOCACHE | _SUN4C_PAGE_VALID)) ==
            _SUN4C_PAGE_VALID) {
                unsigned long left = PAGE_SIZE;
                unsigned long lsize = sun4c_vacinfo.linesize;

                __asm__ __volatile__(
                "add    %2, %2, %%g1\n\t"
                "add    %2, %%g1, %%g2\n\t"
                "add    %2, %%g2, %%g3\n\t"
                "add    %2, %%g3, %%g4\n\t"
                "add    %2, %%g4, %%g5\n\t"
                "add    %2, %%g5, %%o4\n\t"
                "add    %2, %%o4, %%o5\n"
                "1:\n\t"
                "subcc  %1, %%o5, %1\n\t"
                "sta    %%g0, [%0] %6\n\t"
                "sta    %%g0, [%0 + %2] %6\n\t"
                "sta    %%g0, [%0 + %%g1] %6\n\t"
                "sta    %%g0, [%0 + %%g2] %6\n\t"
                "sta    %%g0, [%0 + %%g3] %6\n\t"
                "sta    %%g0, [%0 + %%g4] %6\n\t"
                "sta    %%g0, [%0 + %%g5] %6\n\t"
                "sta    %%g0, [%0 + %%o4] %6\n\t"
                "bg     1b\n\t"
                " add   %0, %%o5, %0\n"
                : "=&r" (addr), "=&r" (left), "=&r" (lsize)
                : "0" (addr), "1" (left), "2" (lsize),
                  "i" (ASI_FLUSHPG)
                : "g1", "g2", "g3", "g4", "g5", "o4", "o5", "cc");
        }
}

/* The sun4c's do have an on chip store buffer.  And the way you
 * clear them out isn't so obvious.  The only way I can think of
 * to accomplish this is to read the current context register,
 * store the same value there, then read an external hardware
 * register.
 */
void sun4c_complete_all_stores(void)
{
        volatile int _unused;

        _unused = sun4c_get_context();
        sun4c_set_context(_unused);
        _unused = get_auxio();
}

/* Bootup utility functions. */
static inline void sun4c_init_clean_segmap(unsigned char pseg)
{
        unsigned long vaddr;

        sun4c_put_segmap(0, pseg);
        for (vaddr = 0; vaddr < SUN4C_REAL_PGDIR_SIZE; vaddr += PAGE_SIZE)
                sun4c_put_pte(vaddr, 0);
        sun4c_put_segmap(0, invalid_segment);
}

static inline void sun4c_init_clean_mmu(unsigned long kernel_end)
{
        unsigned long vaddr;
        unsigned char savectx, ctx;

        savectx = sun4c_get_context();
        for (ctx = 0; ctx < num_contexts; ctx++) {
                sun4c_set_context(ctx);
                for (vaddr = 0; vaddr < 0x20000000; vaddr += SUN4C_REAL_PGDIR_SIZE)
                        sun4c_put_segmap(vaddr, invalid_segment);
                for (vaddr = 0xe0000000; vaddr < KERNBASE; vaddr += SUN4C_REAL_PGDIR_SIZE)
                        sun4c_put_segmap(vaddr, invalid_segment);
                for (vaddr = kernel_end; vaddr < KADB_DEBUGGER_BEGVM; vaddr += SUN4C_REAL_PGDIR_SIZE)
                        sun4c_put_segmap(vaddr, invalid_segment);
                for (vaddr = LINUX_OPPROM_ENDVM; vaddr; vaddr += SUN4C_REAL_PGDIR_SIZE)
                        sun4c_put_segmap(vaddr, invalid_segment);
        }
        sun4c_set_context(savectx);
}

void __init sun4c_probe_vac(void)
{
        sun4c_disable_vac();

        if ((idprom->id_machtype == (SM_SUN4C | SM_4C_SS1)) ||
            (idprom->id_machtype == (SM_SUN4C | SM_4C_SS1PLUS))) {
                /* PROM on SS1 lacks this info, to be super safe we
                 * hard code it here since this arch is cast in stone.
                 */
                sun4c_vacinfo.num_bytes = 65536;
                sun4c_vacinfo.linesize = 16;
        } else {
                sun4c_vacinfo.num_bytes =
                 prom_getintdefault(prom_root_node, "vac-size", 65536);
                sun4c_vacinfo.linesize =
                 prom_getintdefault(prom_root_node, "vac-linesize", 16);
        }
        sun4c_vacinfo.do_hwflushes =
         prom_getintdefault(prom_root_node, "vac-hwflush", 0);

        if (sun4c_vacinfo.do_hwflushes == 0)
                sun4c_vacinfo.do_hwflushes =
                 prom_getintdefault(prom_root_node, "vac_hwflush", 0);

        if (sun4c_vacinfo.num_bytes != 65536) {
                prom_printf("WEIRD Sun4C VAC cache size, "
                            "tell sparclinux@vger.kernel.org");
                prom_halt();
        }

        switch (sun4c_vacinfo.linesize) {
        case 16:
                sun4c_vacinfo.log2lsize = 4;
                break;
        case 32:
                sun4c_vacinfo.log2lsize = 5;
                break;
        default:
                prom_printf("probe_vac: Didn't expect vac-linesize of %d, halting\n",
                            sun4c_vacinfo.linesize);
                prom_halt();
        };

        sun4c_flush_all();
        sun4c_enable_vac();
}

/* Patch instructions for the low level kernel fault handler. */
extern unsigned long invalid_segment_patch1, invalid_segment_patch1_ff;
extern unsigned long invalid_segment_patch2, invalid_segment_patch2_ff;
extern unsigned long invalid_segment_patch1_1ff, invalid_segment_patch2_1ff;
extern unsigned long num_context_patch1, num_context_patch1_16;
extern unsigned long num_context_patch2_16;
extern unsigned long vac_linesize_patch, vac_linesize_patch_32;
extern unsigned long vac_hwflush_patch1, vac_hwflush_patch1_on;
extern unsigned long vac_hwflush_patch2, vac_hwflush_patch2_on;

#define PATCH_INSN(src, dst) do {       \
                daddr = &(dst);         \
                iaddr = &(src);         \
                *daddr = *iaddr;        \
        } while (0)

static void __init patch_kernel_fault_handler(void)
{
        unsigned long *iaddr, *daddr;

        switch (num_segmaps) {
                case 128:
                        /* Default, nothing to do. */
                        break;
                case 256:
                        PATCH_INSN(invalid_segment_patch1_ff,
                                   invalid_segment_patch1);
                        PATCH_INSN(invalid_segment_patch2_ff,
                                   invalid_segment_patch2);
                        break;
                case 512:
                        PATCH_INSN(invalid_segment_patch1_1ff,
                                   invalid_segment_patch1);
                        PATCH_INSN(invalid_segment_patch2_1ff,
                                   invalid_segment_patch2);
                        break;
                default:
                        prom_printf("Unhandled number of segmaps: %d\n",
                                    num_segmaps);
                        prom_halt();
        };
        switch (num_contexts) {
                case 8:
                        /* Default, nothing to do. */
                        break;
                case 16:
                        PATCH_INSN(num_context_patch1_16,
                                   num_context_patch1);
                        break;
                default:
                        prom_printf("Unhandled number of contexts: %d\n",
                                    num_contexts);
                        prom_halt();
        };

        if (sun4c_vacinfo.do_hwflushes != 0) {
                PATCH_INSN(vac_hwflush_patch1_on, vac_hwflush_patch1);
                PATCH_INSN(vac_hwflush_patch2_on, vac_hwflush_patch2);
        } else {
                switch (sun4c_vacinfo.linesize) {
                case 16:
                        /* Default, nothing to do. */
                        break;
                case 32:
                        PATCH_INSN(vac_linesize_patch_32, vac_linesize_patch);
                        break;
                default:
                        prom_printf("Impossible VAC linesize %d, halting...\n",
                                    sun4c_vacinfo.linesize);
                        prom_halt();
                };
        }
}

static void __init sun4c_probe_mmu(void)
{
        if ((idprom->id_machtype == (SM_SUN4C | SM_4C_SS1)) ||
            (idprom->id_machtype == (SM_SUN4C | SM_4C_SS1PLUS))) {
                /* Hardcode these just to be safe, PROM on SS1 does
                * not have this info available in the root node.
                */
                num_segmaps = 128;
                num_contexts = 8;
        } else {
                num_segmaps =
                    prom_getintdefault(prom_root_node, "mmu-npmg", 128);
                num_contexts =
                    prom_getintdefault(prom_root_node, "mmu-nctx", 0x8);
        }
        patch_kernel_fault_handler();
}

volatile unsigned long __iomem *sun4c_memerr_reg = NULL;

void __init sun4c_probe_memerr_reg(void)
{
        int node;
        struct linux_prom_registers regs[1];

        node = prom_getchild(prom_root_node);
        node = prom_searchsiblings(prom_root_node, "memory-error");
        if (!node)
                return;
        if (prom_getproperty(node, "reg", (char *)regs, sizeof(regs)) <= 0)
                return;
        /* hmm I think regs[0].which_io is zero here anyways */
        sun4c_memerr_reg = ioremap(regs[0].phys_addr, regs[0].reg_size);
}

static inline void sun4c_init_ss2_cache_bug(void)
{
        extern unsigned long start;

        if ((idprom->id_machtype == (SM_SUN4C | SM_4C_SS2)) ||
            (idprom->id_machtype == (SM_SUN4C | SM_4C_IPX)) ||
            (idprom->id_machtype == (SM_SUN4C | SM_4C_ELC))) {
                /* Whee.. */
                printk("SS2 cache bug detected, uncaching trap table page\n");
                sun4c_flush_page((unsigned int) &start);
                sun4c_put_pte(((unsigned long) &start),
                        (sun4c_get_pte((unsigned long) &start) | _SUN4C_PAGE_NOCACHE));
        }
}

/* Addr is always aligned on a page boundary for us already. */
static int sun4c_map_dma_area(struct device *dev, dma_addr_t *pba, unsigned long va,
                              unsigned long addr, int len)
{
        unsigned long page, end;

        *pba = addr;

        end = PAGE_ALIGN((addr + len));
        while (addr < end) {
                page = va;
                sun4c_flush_page(page);
                page -= PAGE_OFFSET;
                page >>= PAGE_SHIFT;
                page |= (_SUN4C_PAGE_VALID | _SUN4C_PAGE_DIRTY |
                         _SUN4C_PAGE_NOCACHE | _SUN4C_PAGE_PRIV);
                sun4c_put_pte(addr, page);
                addr += PAGE_SIZE;
                va += PAGE_SIZE;
        }

        return 0;
}

static void sun4c_unmap_dma_area(struct device *dev, unsigned long busa, int len)
{
        /* Fortunately for us, bus_addr == uncached_virt in sun4c. */
        /* XXX Implement this */
}

/* TLB management. */

/* Don't change this struct without changing entry.S. This is used
 * in the in-window kernel fault handler, and you don't want to mess
 * with that. (See sun4c_fault in entry.S).
 */
struct sun4c_mmu_entry {
        struct sun4c_mmu_entry *next;
        struct sun4c_mmu_entry *prev;
        unsigned long vaddr;
        unsigned char pseg;
        unsigned char locked;

        /* For user mappings only, and completely hidden from kernel
         * TLB miss code.
         */
        unsigned char ctx;
        struct sun4c_mmu_entry *lru_next;
        struct sun4c_mmu_entry *lru_prev;
};

static struct sun4c_mmu_entry mmu_entry_pool[SUN4C_MAX_SEGMAPS];

static void __init sun4c_init_mmu_entry_pool(void)
{
        int i;

        for (i=0; i < SUN4C_MAX_SEGMAPS; i++) {
                mmu_entry_pool[i].pseg = i;
                mmu_entry_pool[i].next = NULL;
                mmu_entry_pool[i].prev = NULL;
                mmu_entry_pool[i].vaddr = 0;
                mmu_entry_pool[i].locked = 0;
                mmu_entry_pool[i].ctx = 0;
                mmu_entry_pool[i].lru_next = NULL;
                mmu_entry_pool[i].lru_prev = NULL;
        }
        mmu_entry_pool[invalid_segment].locked = 1;
}

static inline void fix_permissions(unsigned long vaddr, unsigned long bits_on,
                                   unsigned long bits_off)
{
        unsigned long start, end;

        end = vaddr + SUN4C_REAL_PGDIR_SIZE;
        for (start = vaddr; start < end; start += PAGE_SIZE)
                if (sun4c_get_pte(start) & _SUN4C_PAGE_VALID)
                        sun4c_put_pte(start, (sun4c_get_pte(start) | bits_on) &
                                      ~bits_off);
}

static inline void sun4c_init_map_kernelprom(unsigned long kernel_end)
{
        unsigned long vaddr;
        unsigned char pseg, ctx;

        for (vaddr = KADB_DEBUGGER_BEGVM;
             vaddr < LINUX_OPPROM_ENDVM;
             vaddr += SUN4C_REAL_PGDIR_SIZE) {
                pseg = sun4c_get_segmap(vaddr);
                if (pseg != invalid_segment) {
                        mmu_entry_pool[pseg].locked = 1;
                        for (ctx = 0; ctx < num_contexts; ctx++)
                                prom_putsegment(ctx, vaddr, pseg);
                        fix_permissions(vaddr, _SUN4C_PAGE_PRIV, 0);
                }
        }

        for (vaddr = KERNBASE; vaddr < kernel_end; vaddr += SUN4C_REAL_PGDIR_SIZE) {
                pseg = sun4c_get_segmap(vaddr);
                mmu_entry_pool[pseg].locked = 1;
                for (ctx = 0; ctx < num_contexts; ctx++)
                        prom_putsegment(ctx, vaddr, pseg);
                fix_permissions(vaddr, _SUN4C_PAGE_PRIV, _SUN4C_PAGE_NOCACHE);
        }
}

static void __init sun4c_init_lock_area(unsigned long start, unsigned long end)
{
        int i, ctx;

        while (start < end) {
                for (i = 0; i < invalid_segment; i++)
                        if (!mmu_entry_pool[i].locked)
                                break;
                mmu_entry_pool[i].locked = 1;
                sun4c_init_clean_segmap(i);
                for (ctx = 0; ctx < num_contexts; ctx++)
                        prom_putsegment(ctx, start, mmu_entry_pool[i].pseg);
                start += SUN4C_REAL_PGDIR_SIZE;
        }
}

/* Don't change this struct without changing entry.S. This is used
 * in the in-window kernel fault handler, and you don't want to mess
 * with that. (See sun4c_fault in entry.S).
 */
struct sun4c_mmu_ring {
        struct sun4c_mmu_entry ringhd;
        int num_entries;
};

static struct sun4c_mmu_ring sun4c_context_ring[SUN4C_MAX_CONTEXTS]; /* used user entries */
static struct sun4c_mmu_ring sun4c_ufree_ring;       /* free user entries */
static struct sun4c_mmu_ring sun4c_ulru_ring;        /* LRU user entries */
struct sun4c_mmu_ring sun4c_kernel_ring;      /* used kernel entries */
struct sun4c_mmu_ring sun4c_kfree_ring;       /* free kernel entries */

static inline void sun4c_init_rings(void)
{
        int i;

        for (i = 0; i < SUN4C_MAX_CONTEXTS; i++) {
                sun4c_context_ring[i].ringhd.next =
                        sun4c_context_ring[i].ringhd.prev =
                        &sun4c_context_ring[i].ringhd;
                sun4c_context_ring[i].num_entries = 0;
        }
        sun4c_ufree_ring.ringhd.next = sun4c_ufree_ring.ringhd.prev =
                &sun4c_ufree_ring.ringhd;
        sun4c_ufree_ring.num_entries = 0;
        sun4c_ulru_ring.ringhd.lru_next = sun4c_ulru_ring.ringhd.lru_prev =
                &sun4c_ulru_ring.ringhd;
        sun4c_ulru_ring.num_entries = 0;
        sun4c_kernel_ring.ringhd.next = sun4c_kernel_ring.ringhd.prev =
                &sun4c_kernel_ring.ringhd;
        sun4c_kernel_ring.num_entries = 0;
        sun4c_kfree_ring.ringhd.next = sun4c_kfree_ring.ringhd.prev =
                &sun4c_kfree_ring.ringhd;
        sun4c_kfree_ring.num_entries = 0;
}

static void add_ring(struct sun4c_mmu_ring *ring,
                     struct sun4c_mmu_entry *entry)
{
        struct sun4c_mmu_entry *head = &ring->ringhd;

        entry->prev = head;
        (entry->next = head->next)->prev = entry;
        head->next = entry;
        ring->num_entries++;
}

static inline void add_lru(struct sun4c_mmu_entry *entry)
{
        struct sun4c_mmu_ring *ring = &sun4c_ulru_ring;
        struct sun4c_mmu_entry *head = &ring->ringhd;

        entry->lru_next = head;
        (entry->lru_prev = head->lru_prev)->lru_next = entry;
        head->lru_prev = entry;
}

static void add_ring_ordered(struct sun4c_mmu_ring *ring,
                             struct sun4c_mmu_entry *entry)
{
        struct sun4c_mmu_entry *head = &ring->ringhd;
        unsigned long addr = entry->vaddr;

        while ((head->next != &ring->ringhd) && (head->next->vaddr < addr))
                head = head->next;

        entry->prev = head;
        (entry->next = head->next)->prev = entry;
        head->next = entry;
        ring->num_entries++;

        add_lru(entry);
}

static inline void remove_ring(struct sun4c_mmu_ring *ring,
                                   struct sun4c_mmu_entry *entry)
{
        struct sun4c_mmu_entry *next = entry->next;

        (next->prev = entry->prev)->next = next;
        ring->num_entries--;
}

static void remove_lru(struct sun4c_mmu_entry *entry)
{
        struct sun4c_mmu_entry *next = entry->lru_next;

        (next->lru_prev = entry->lru_prev)->lru_next = next;
}

static void free_user_entry(int ctx, struct sun4c_mmu_entry *entry)
{
        remove_ring(sun4c_context_ring+ctx, entry);
        remove_lru(entry);
        add_ring(&sun4c_ufree_ring, entry);
}

static void free_kernel_entry(struct sun4c_mmu_entry *entry,
                              struct sun4c_mmu_ring *ring)
{
        remove_ring(ring, entry);
        add_ring(&sun4c_kfree_ring, entry);
}

static void __init sun4c_init_fill_kernel_ring(int howmany)
{
        int i;

        while (howmany) {
                for (i = 0; i < invalid_segment; i++)
                        if (!mmu_entry_pool[i].locked)
                                break;
                mmu_entry_pool[i].locked = 1;
                sun4c_init_clean_segmap(i);
                add_ring(&sun4c_kfree_ring, &mmu_entry_pool[i]);
                howmany--;
        }
}

static void __init sun4c_init_fill_user_ring(void)
{
        int i;

        for (i = 0; i < invalid_segment; i++) {
                if (mmu_entry_pool[i].locked)
                        continue;
                sun4c_init_clean_segmap(i);
                add_ring(&sun4c_ufree_ring, &mmu_entry_pool[i]);
        }
}

static void sun4c_kernel_unmap(struct sun4c_mmu_entry *kentry)
{
        int savectx, ctx;

        savectx = sun4c_get_context();
        for (ctx = 0; ctx < num_contexts; ctx++) {
                sun4c_set_context(ctx);
                sun4c_put_segmap(kentry->vaddr, invalid_segment);
        }
        sun4c_set_context(savectx);
}

static void sun4c_kernel_map(struct sun4c_mmu_entry *kentry)
{
        int savectx, ctx;

        savectx = sun4c_get_context();
        for (ctx = 0; ctx < num_contexts; ctx++) {
                sun4c_set_context(ctx);
                sun4c_put_segmap(kentry->vaddr, kentry->pseg);
        }
        sun4c_set_context(savectx);
}

#define sun4c_user_unmap(__entry) \
        sun4c_put_segmap((__entry)->vaddr, invalid_segment)

static void sun4c_demap_context(struct sun4c_mmu_ring *crp, unsigned char ctx)
{
        struct sun4c_mmu_entry *head = &crp->ringhd;
        unsigned long flags;

        local_irq_save(flags);
        if (head->next != head) {
                struct sun4c_mmu_entry *entry = head->next;
                int savectx = sun4c_get_context();

                flush_user_windows();
                sun4c_set_context(ctx);
                sun4c_flush_context();
                do {
                        struct sun4c_mmu_entry *next = entry->next;

                        sun4c_user_unmap(entry);
                        free_user_entry(ctx, entry);

                        entry = next;
                } while (entry != head);
                sun4c_set_context(savectx);
        }
        local_irq_restore(flags);
}

static int sun4c_user_taken_entries;  /* This is how much we have.             */
static int max_user_taken_entries;    /* This limits us and prevents deadlock. */

static struct sun4c_mmu_entry *sun4c_kernel_strategy(void)
{
        struct sun4c_mmu_entry *this_entry;

        /* If some are free, return first one. */
        if (sun4c_kfree_ring.num_entries) {
                this_entry = sun4c_kfree_ring.ringhd.next;
                return this_entry;
        }

        /* Else free one up. */
        this_entry = sun4c_kernel_ring.ringhd.prev;
        sun4c_flush_segment(this_entry->vaddr);
        sun4c_kernel_unmap(this_entry);
        free_kernel_entry(this_entry, &sun4c_kernel_ring);
        this_entry = sun4c_kfree_ring.ringhd.next;

        return this_entry;
}

/* Using this method to free up mmu entries eliminates a lot of
 * potential races since we have a kernel that incurs tlb
 * replacement faults.  There may be performance penalties.
 *
 * NOTE: Must be called with interrupts disabled.
 */
static struct sun4c_mmu_entry *sun4c_user_strategy(void)
{
        struct sun4c_mmu_entry *entry;
        unsigned char ctx;
        int savectx;

        /* If some are free, return first one. */
        if (sun4c_ufree_ring.num_entries) {
                entry = sun4c_ufree_ring.ringhd.next;
                goto unlink_out;
        }

        if (sun4c_user_taken_entries) {
                entry = sun4c_kernel_strategy();
                sun4c_user_taken_entries--;
                goto kunlink_out;
        }

        /* Grab from the beginning of the LRU list. */
        entry = sun4c_ulru_ring.ringhd.lru_next;
        ctx = entry->ctx;

        savectx = sun4c_get_context();
        flush_user_windows();
        sun4c_set_context(ctx);
        sun4c_flush_segment(entry->vaddr);
        sun4c_user_unmap(entry);
        remove_ring(sun4c_context_ring + ctx, entry);
        remove_lru(entry);
        sun4c_set_context(savectx);

        return entry;

unlink_out:
        remove_ring(&sun4c_ufree_ring, entry);
        return entry;
kunlink_out:
        remove_ring(&sun4c_kfree_ring, entry);
        return entry;
}

/* NOTE: Must be called with interrupts disabled. */
void sun4c_grow_kernel_ring(void)
{
        struct sun4c_mmu_entry *entry;

        /* Prevent deadlock condition. */
        if (sun4c_user_taken_entries >= max_user_taken_entries)
                return;

        if (sun4c_ufree_ring.num_entries) {
                entry = sun4c_ufree_ring.ringhd.next;
                remove_ring(&sun4c_ufree_ring, entry);
                add_ring(&sun4c_kfree_ring, entry);
                sun4c_user_taken_entries++;
        }
}

/* 2 page buckets for task struct and kernel stack allocation.
 *
 * TASK_STACK_BEGIN
 * bucket[0]
 * bucket[1]
 *   [ ... ]
 * bucket[NR_TASK_BUCKETS-1]
 * TASK_STACK_BEGIN + (sizeof(struct task_bucket) * NR_TASK_BUCKETS)
 *
 * Each slot looks like:
 *
 *  page 1 --  task struct + beginning of kernel stack
 *  page 2 --  rest of kernel stack
 */

union task_union *sun4c_bucket[NR_TASK_BUCKETS];

static int sun4c_lowbucket_avail;

#define BUCKET_EMPTY     ((union task_union *) 0)
#define BUCKET_SHIFT     (PAGE_SHIFT + 1)        /* log2(sizeof(struct task_bucket)) */
#define BUCKET_SIZE      (1 << BUCKET_SHIFT)
#define BUCKET_NUM(addr) ((((addr) - SUN4C_LOCK_VADDR) >> BUCKET_SHIFT))
#define BUCKET_ADDR(num) (((num) << BUCKET_SHIFT) + SUN4C_LOCK_VADDR)
#define BUCKET_PTE(page)       \
        ((((page) - PAGE_OFFSET) >> PAGE_SHIFT) | pgprot_val(SUN4C_PAGE_KERNEL))
#define BUCKET_PTE_PAGE(pte)   \
        (PAGE_OFFSET + (((pte) & SUN4C_PFN_MASK) << PAGE_SHIFT))

static void get_locked_segment(unsigned long addr)
{
        struct sun4c_mmu_entry *stolen;
        unsigned long flags;

        local_irq_save(flags);
        addr &= SUN4C_REAL_PGDIR_MASK;
        stolen = sun4c_user_strategy();
        max_user_taken_entries--;
        stolen->vaddr = addr;
        flush_user_windows();
        sun4c_kernel_map(stolen);
        local_irq_restore(flags);
}

static void free_locked_segment(unsigned long addr)
{
        struct sun4c_mmu_entry *entry;
        unsigned long flags;
        unsigned char pseg;

        local_irq_save(flags);
        addr &= SUN4C_REAL_PGDIR_MASK;
        pseg = sun4c_get_segmap(addr);
        entry = &mmu_entry_pool[pseg];

        flush_user_windows();
        sun4c_flush_segment(addr);
        sun4c_kernel_unmap(entry);
        add_ring(&sun4c_ufree_ring, entry);
        max_user_taken_entries++;
        local_irq_restore(flags);
}

static inline void garbage_collect(int entry)
{
        int start, end;

        /* 32 buckets per segment... */
        entry &= ~31;
        start = entry;
        for (end = (start + 32); start < end; start++)
                if (sun4c_bucket[start] != BUCKET_EMPTY)
                        return;

        /* Entire segment empty, release it. */
        free_locked_segment(BUCKET_ADDR(entry));
}

static struct thread_info *sun4c_alloc_thread_info(void)
{
        unsigned long addr, pages;
        int entry;

        pages = __get_free_pages(GFP_KERNEL, THREAD_INFO_ORDER);
        if (!pages)
                return NULL;

        for (entry = sun4c_lowbucket_avail; entry < NR_TASK_BUCKETS; entry++)
                if (sun4c_bucket[entry] == BUCKET_EMPTY)
                        break;
        if (entry == NR_TASK_BUCKETS) {
                free_pages(pages, THREAD_INFO_ORDER);
                return NULL;
        }
        if (entry >= sun4c_lowbucket_avail)
                sun4c_lowbucket_avail = entry + 1;

        addr = BUCKET_ADDR(entry);
        sun4c_bucket[entry] = (union task_union *) addr;
        if(sun4c_get_segmap(addr) == invalid_segment)
                get_locked_segment(addr);

        /* We are changing the virtual color of the page(s)
         * so we must flush the cache to guarantee consistency.
         */
        sun4c_flush_page(pages);
        sun4c_flush_page(pages + PAGE_SIZE);

        sun4c_put_pte(addr, BUCKET_PTE(pages));
        sun4c_put_pte(addr + PAGE_SIZE, BUCKET_PTE(pages + PAGE_SIZE));

#ifdef CONFIG_DEBUG_STACK_USAGE
        memset((void *)addr, 0, PAGE_SIZE << THREAD_INFO_ORDER);
#endif /* DEBUG_STACK_USAGE */

        return (struct thread_info *) addr;
}

static void sun4c_free_thread_info(struct thread_info *ti)
{
        unsigned long tiaddr = (unsigned long) ti;
        unsigned long pages = BUCKET_PTE_PAGE(sun4c_get_pte(tiaddr));
        int entry = BUCKET_NUM(tiaddr);

        /* We are deleting a mapping, so the flush here is mandatory. */
        sun4c_flush_page(tiaddr);
        sun4c_flush_page(tiaddr + PAGE_SIZE);

        sun4c_put_pte(tiaddr, 0);
        sun4c_put_pte(tiaddr + PAGE_SIZE, 0);

        sun4c_bucket[entry] = BUCKET_EMPTY;
        if (entry < sun4c_lowbucket_avail)
                sun4c_lowbucket_avail = entry;

        free_pages(pages, THREAD_INFO_ORDER);
        garbage_collect(entry);
}

static void __init sun4c_init_buckets(void)
{
        int entry;

        if (sizeof(union thread_union) != (PAGE_SIZE << THREAD_INFO_ORDER)) {
                extern void thread_info_size_is_bolixed_pete(void);
                thread_info_size_is_bolixed_pete();
        }

        for (entry = 0; entry < NR_TASK_BUCKETS; entry++)
                sun4c_bucket[entry] = BUCKET_EMPTY;
        sun4c_lowbucket_avail = 0;
}

static unsigned long sun4c_iobuffer_start;
static unsigned long sun4c_iobuffer_end;
static unsigned long sun4c_iobuffer_high;
static unsigned long *sun4c_iobuffer_map;
static int iobuffer_map_size;

/*
 * Alias our pages so they do not cause a trap.
 * Also one page may be aliased into several I/O areas and we may
 * finish these I/O separately.
 */
static char *sun4c_lockarea(char *vaddr, unsigned long size)
{
        unsigned long base, scan;
        unsigned long npages;
        unsigned long vpage;
        unsigned long pte;
        unsigned long apage;
        unsigned long high;
        unsigned long flags;

        npages = (((unsigned long)vaddr & ~PAGE_MASK) +
                  size + (PAGE_SIZE-1)) >> PAGE_SHIFT;

        scan = 0;
        local_irq_save(flags);
        for (;;) {
                scan = find_next_zero_bit(sun4c_iobuffer_map,
                                          iobuffer_map_size, scan);
                if ((base = scan) + npages > iobuffer_map_size) goto abend;
                for (;;) {
                        if (scan >= base + npages) goto found;
                        if (test_bit(scan, sun4c_iobuffer_map)) break;
                        scan++;
                }
        }

found:
        high = ((base + npages) << PAGE_SHIFT) + sun4c_iobuffer_start;
        high = SUN4C_REAL_PGDIR_ALIGN(high);
        while (high > sun4c_iobuffer_high) {
                get_locked_segment(sun4c_iobuffer_high);
                sun4c_iobuffer_high += SUN4C_REAL_PGDIR_SIZE;
        }

        vpage = ((unsigned long) vaddr) & PAGE_MASK;
        for (scan = base; scan < base+npages; scan++) {
                pte = ((vpage-PAGE_OFFSET) >> PAGE_SHIFT);
                pte |= pgprot_val(SUN4C_PAGE_KERNEL);
                pte |= _SUN4C_PAGE_NOCACHE;
                set_bit(scan, sun4c_iobuffer_map);
                apage = (scan << PAGE_SHIFT) + sun4c_iobuffer_start;

                /* Flush original mapping so we see the right things later. */
                sun4c_flush_page(vpage);

                sun4c_put_pte(apage, pte);
                vpage += PAGE_SIZE;
        }
        local_irq_restore(flags);
        return (char *) ((base << PAGE_SHIFT) + sun4c_iobuffer_start +
                         (((unsigned long) vaddr) & ~PAGE_MASK));

abend:
        local_irq_restore(flags);
        printk("DMA vaddr=0x%p size=%08lx\n", vaddr, size);
        panic("Out of iobuffer table");
        return NULL;
}

static void sun4c_unlockarea(char *vaddr, unsigned long size)
{
        unsigned long vpage, npages;
        unsigned long flags;
        int scan, high;

        vpage = (unsigned long)vaddr & PAGE_MASK;
        npages = (((unsigned long)vaddr & ~PAGE_MASK) +
                  size + (PAGE_SIZE-1)) >> PAGE_SHIFT;

        local_irq_save(flags);
        while (npages != 0) {
                --npages;

                /* This mapping is marked non-cachable, no flush necessary. */
                sun4c_put_pte(vpage, 0);
                clear_bit((vpage - sun4c_iobuffer_start) >> PAGE_SHIFT,
                          sun4c_iobuffer_map);
                vpage += PAGE_SIZE;
        }

        /* garbage collect */
        scan = (sun4c_iobuffer_high - sun4c_iobuffer_start) >> PAGE_SHIFT;
        while (scan >= 0 && !sun4c_iobuffer_map[scan >> 5])
                scan -= 32;
        scan += 32;
        high = sun4c_iobuffer_start + (scan << PAGE_SHIFT);
        high = SUN4C_REAL_PGDIR_ALIGN(high) + SUN4C_REAL_PGDIR_SIZE;
        while (high < sun4c_iobuffer_high) {
                sun4c_iobuffer_high -= SUN4C_REAL_PGDIR_SIZE;
                free_locked_segment(sun4c_iobuffer_high);
        }
        local_irq_restore(flags);
}

/* Note the scsi code at init time passes to here buffers
 * which sit on the kernel stack, those are already locked
 * by implication and fool the page locking code above
 * if passed to by mistake.
 */
static __u32 sun4c_get_scsi_one(struct device *dev, char *bufptr, unsigned long len)
{
        unsigned long page;

        page = ((unsigned long)bufptr) & PAGE_MASK;
        if (!virt_addr_valid(page)) {
                sun4c_flush_page(page);
                return (__u32)bufptr; /* already locked */
        }
        return (__u32)sun4c_lockarea(bufptr, len);
}

static void sun4c_get_scsi_sgl(struct device *dev, struct scatterlist *sg, int sz)
{
        while (sz != 0) {
                --sz;
                sg->dma_address = (__u32)sun4c_lockarea(sg_virt(sg), sg->length);
                sg->dma_length = sg->length;
                sg = sg_next(sg);
        }
}

static void sun4c_release_scsi_one(struct device *dev, __u32 bufptr, unsigned long len)
{
        if (bufptr < sun4c_iobuffer_start)
                return; /* On kernel stack or similar, see above */
        sun4c_unlockarea((char *)bufptr, len);
}

static void sun4c_release_scsi_sgl(struct device *dev, struct scatterlist *sg, int sz)
{
        while (sz != 0) {
                --sz;
                sun4c_unlockarea((char *)sg->dma_address, sg->length);
                sg = sg_next(sg);
        }
}

#define TASK_ENTRY_SIZE    BUCKET_SIZE /* see above */
#define LONG_ALIGN(x) (((x)+(sizeof(long))-1)&~((sizeof(long))-1))

struct vm_area_struct sun4c_kstack_vma;

static void __init sun4c_init_lock_areas(void)
{
        unsigned long sun4c_taskstack_start;
        unsigned long sun4c_taskstack_end;
        int bitmap_size;

        sun4c_init_buckets();
        sun4c_taskstack_start = SUN4C_LOCK_VADDR;
        sun4c_taskstack_end = (sun4c_taskstack_start +
                               (TASK_ENTRY_SIZE * NR_TASK_BUCKETS));
        if (sun4c_taskstack_end >= SUN4C_LOCK_END) {
                prom_printf("Too many tasks, decrease NR_TASK_BUCKETS please.\n");
                prom_halt();
        }

        sun4c_iobuffer_start = sun4c_iobuffer_high =
                                SUN4C_REAL_PGDIR_ALIGN(sun4c_taskstack_end);
        sun4c_iobuffer_end = SUN4C_LOCK_END;
        bitmap_size = (sun4c_iobuffer_end - sun4c_iobuffer_start) >> PAGE_SHIFT;
        bitmap_size = (bitmap_size + 7) >> 3;
        bitmap_size = LONG_ALIGN(bitmap_size);
        iobuffer_map_size = bitmap_size << 3;
        sun4c_iobuffer_map = __alloc_bootmem(bitmap_size, SMP_CACHE_BYTES, 0UL);
        memset((void *) sun4c_iobuffer_map, 0, bitmap_size);

        sun4c_kstack_vma.vm_mm = &init_mm;
        sun4c_kstack_vma.vm_start = sun4c_taskstack_start;
        sun4c_kstack_vma.vm_end = sun4c_taskstack_end;
        sun4c_kstack_vma.vm_page_prot = PAGE_SHARED;
        sun4c_kstack_vma.vm_flags = VM_READ | VM_WRITE | VM_EXEC;
        insert_vm_struct(&init_mm, &sun4c_kstack_vma);
}

/* Cache flushing on the sun4c. */
static void sun4c_flush_cache_all(void)
{
        unsigned long begin, end;

        flush_user_windows();
        begin = (KERNBASE + SUN4C_REAL_PGDIR_SIZE);
        end = (begin + SUN4C_VAC_SIZE);

        if (sun4c_vacinfo.linesize == 32) {
                while (begin < end) {
                        __asm__ __volatile__(
                        "ld     [%0 + 0x00], %%g0\n\t"
                        "ld     [%0 + 0x20], %%g0\n\t"
                        "ld     [%0 + 0x40], %%g0\n\t"
                        "ld     [%0 + 0x60], %%g0\n\t"
                        "ld     [%0 + 0x80], %%g0\n\t"
                        "ld     [%0 + 0xa0], %%g0\n\t"
                        "ld     [%0 + 0xc0], %%g0\n\t"
                        "ld     [%0 + 0xe0], %%g0\n\t"
                        "ld     [%0 + 0x100], %%g0\n\t"
                        "ld     [%0 + 0x120], %%g0\n\t"
                        "ld     [%0 + 0x140], %%g0\n\t"
                        "ld     [%0 + 0x160], %%g0\n\t"
                        "ld     [%0 + 0x180], %%g0\n\t"
                        "ld     [%0 + 0x1a0], %%g0\n\t"
                        "ld     [%0 + 0x1c0], %%g0\n\t"
                        "ld     [%0 + 0x1e0], %%g0\n"
                        : : "r" (begin));
                        begin += 512;
                }
        } else {
                while (begin < end) {
                        __asm__ __volatile__(
                        "ld     [%0 + 0x00], %%g0\n\t"
                        "ld     [%0 + 0x10], %%g0\n\t"
                        "ld     [%0 + 0x20], %%g0\n\t"
                        "ld     [%0 + 0x30], %%g0\n\t"
                        "ld     [%0 + 0x40], %%g0\n\t"
                        "ld     [%0 + 0x50], %%g0\n\t"
                        "ld     [%0 + 0x60], %%g0\n\t"
                        "ld     [%0 + 0x70], %%g0\n\t"
                        "ld     [%0 + 0x80], %%g0\n\t"
                        "ld     [%0 + 0x90], %%g0\n\t"
                        "ld     [%0 + 0xa0], %%g0\n\t"
                        "ld     [%0 + 0xb0], %%g0\n\t"
                        "ld     [%0 + 0xc0], %%g0\n\t"
                        "ld     [%0 + 0xd0], %%g0\n\t"
                        "ld     [%0 + 0xe0], %%g0\n\t"
                        "ld     [%0 + 0xf0], %%g0\n"
                        : : "r" (begin));
                        begin += 256;
                }
        }
}

static void sun4c_flush_cache_mm(struct mm_struct *mm)
{
        int new_ctx = mm->context;

        if (new_ctx != NO_CONTEXT) {
                flush_user_windows();

                if (sun4c_context_ring[new_ctx].num_entries) {
                        struct sun4c_mmu_entry *head = &sun4c_context_ring[new_ctx].ringhd;
                        unsigned long flags;

                        local_irq_save(flags);
                        if (head->next != head) {
                                struct sun4c_mmu_entry *entry = head->next;
                                int savectx = sun4c_get_context();

                                sun4c_set_context(new_ctx);
                                sun4c_flush_context();
                                do {
                                        struct sun4c_mmu_entry *next = entry->next;

                                        sun4c_user_unmap(entry);
                                        free_user_entry(new_ctx, entry);

                                        entry = next;
                                } while (entry != head);
                                sun4c_set_context(savectx);
                        }
                        local_irq_restore(flags);
                }
        }
}

static void sun4c_flush_cache_range(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
        struct mm_struct *mm = vma->vm_mm;
        int new_ctx = mm->context;

        if (new_ctx != NO_CONTEXT) {
                struct sun4c_mmu_entry *head = &sun4c_context_ring[new_ctx].ringhd;
                struct sun4c_mmu_entry *entry;
                unsigned long flags;

                flush_user_windows();

                local_irq_save(flags);
                /* All user segmap chains are ordered on entry->vaddr. */
                for (entry = head->next;
                     (entry != head) && ((entry->vaddr+SUN4C_REAL_PGDIR_SIZE) < start);
                     entry = entry->next)
                        ;

                /* Tracing various job mixtures showed that this conditional
                 * only passes ~35% of the time for most worse case situations,
                 * therefore we avoid all of this gross overhead ~65% of the time.
                 */
                if ((entry != head) && (entry->vaddr < end)) {
                        int octx = sun4c_get_context();
                        sun4c_set_context(new_ctx);

                        /* At this point, always, (start >= entry->vaddr) and
                         * (entry->vaddr < end), once the latter condition
                         * ceases to hold, or we hit the end of the list, we
                         * exit the loop.  The ordering of all user allocated
                         * segmaps makes this all work out so beautifully.
                         */
                        do {
                                struct sun4c_mmu_entry *next = entry->next;
                                unsigned long realend;

                                /* "realstart" is always >= entry->vaddr */
                                realend = entry->vaddr + SUN4C_REAL_PGDIR_SIZE;
                                if (end < realend)
                                        realend = end;
                                if ((realend - entry->vaddr) <= (PAGE_SIZE << 3)) {
                                        unsigned long page = entry->vaddr;
                                        while (page < realend) {
                                                sun4c_flush_page(page);
                                                page += PAGE_SIZE;
                                        }
                                } else {
                                        sun4c_flush_segment(entry->vaddr);
                                        sun4c_user_unmap(entry);
                                        free_user_entry(new_ctx, entry);
                                }
                                entry = next;
                        } while ((entry != head) && (entry->vaddr < end));
                        sun4c_set_context(octx);
                }
                local_irq_restore(flags);
        }
}

static void sun4c_flush_cache_page(struct vm_area_struct *vma, unsigned long page)
{
        struct mm_struct *mm = vma->vm_mm;
        int new_ctx = mm->context;

        /* Sun4c has no separate I/D caches so cannot optimize for non
         * text page flushes.
         */
        if (new_ctx != NO_CONTEXT) {
                int octx = sun4c_get_context();
                unsigned long flags;

                flush_user_windows();
                local_irq_save(flags);
                sun4c_set_context(new_ctx);
                sun4c_flush_page(page);
                sun4c_set_context(octx);
                local_irq_restore(flags);
        }
}

static void sun4c_flush_page_to_ram(unsigned long page)
{
        unsigned long flags;

        local_irq_save(flags);
        sun4c_flush_page(page);
        local_irq_restore(flags);
}

/* Sun4c cache is unified, both instructions and data live there, so
 * no need to flush the on-stack instructions for new signal handlers.
 */
static void sun4c_flush_sig_insns(struct mm_struct *mm, unsigned long insn_addr)
{
}

/* TLB flushing on the sun4c.  These routines count on the cache
 * flushing code to flush the user register windows so that we need
 * not do so when we get here.
 */

static void sun4c_flush_tlb_all(void)
{
        struct sun4c_mmu_entry *this_entry, *next_entry;
        unsigned long flags;
        int savectx, ctx;

        local_irq_save(flags);
        this_entry = sun4c_kernel_ring.ringhd.next;
        savectx = sun4c_get_context();
        flush_user_windows();
        while (sun4c_kernel_ring.num_entries) {
                next_entry = this_entry->next;
                sun4c_flush_segment(this_entry->vaddr);
                for (ctx = 0; ctx < num_contexts; ctx++) {
                        sun4c_set_context(ctx);
                        sun4c_put_segmap(this_entry->vaddr, invalid_segment);
                }
                free_kernel_entry(this_entry, &sun4c_kernel_ring);
                this_entry = next_entry;
        }
        sun4c_set_context(savectx);
        local_irq_restore(flags);
}

static void sun4c_flush_tlb_mm(struct mm_struct *mm)
{
        int new_ctx = mm->context;

        if (new_ctx != NO_CONTEXT) {
                struct sun4c_mmu_entry *head = &sun4c_context_ring[new_ctx].ringhd;
                unsigned long flags;

                local_irq_save(flags);
                if (head->next != head) {
                        struct sun4c_mmu_entry *entry = head->next;
                        int savectx = sun4c_get_context();

                        sun4c_set_context(new_ctx);
                        sun4c_flush_context();
                        do {
                                struct sun4c_mmu_entry *next = entry->next;

                                sun4c_user_unmap(entry);
                                free_user_entry(new_ctx, entry);

                                entry = next;
                        } while (entry != head);
                        sun4c_set_context(savectx);
                }
                local_irq_restore(flags);
        }
}

static void sun4c_flush_tlb_range(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
        struct mm_struct *mm = vma->vm_mm;
        int new_ctx = mm->context;

        if (new_ctx != NO_CONTEXT) {
                struct sun4c_mmu_entry *head = &sun4c_context_ring[new_ctx].ringhd;
                struct sun4c_mmu_entry *entry;
                unsigned long flags;

                local_irq_save(flags);
                /* See commentary in sun4c_flush_cache_range(). */
                for (entry = head->next;
                     (entry != head) && ((entry->vaddr+SUN4C_REAL_PGDIR_SIZE) < start);
                     entry = entry->next)
                        ;

                if ((entry != head) && (entry->vaddr < end)) {
                        int octx = sun4c_get_context();

                        sun4c_set_context(new_ctx);
                        do {
                                struct sun4c_mmu_entry *next = entry->next;

                                sun4c_flush_segment(entry->vaddr);
                                sun4c_user_unmap(entry);
                                free_user_entry(new_ctx, entry);

                                entry = next;
                        } while ((entry != head) && (entry->vaddr < end));
                        sun4c_set_context(octx);
                }
                local_irq_restore(flags);
        }
}

static void sun4c_flush_tlb_page(struct vm_area_struct *vma, unsigned long page)
{
        struct mm_struct *mm = vma->vm_mm;
        int new_ctx = mm->context;

        if (new_ctx != NO_CONTEXT) {
                int savectx = sun4c_get_context();
                unsigned long flags;

                local_irq_save(flags);
                sun4c_set_context(new_ctx);
                page &= PAGE_MASK;
                sun4c_flush_page(page);
                sun4c_put_pte(page, 0);
                sun4c_set_context(savectx);
                local_irq_restore(flags);
        }
}

static inline void sun4c_mapioaddr(unsigned long physaddr, unsigned long virt_addr)
{
        unsigned long page_entry, pg_iobits;

        pg_iobits = _SUN4C_PAGE_PRESENT | _SUN4C_READABLE | _SUN4C_WRITEABLE |
                    _SUN4C_PAGE_IO | _SUN4C_PAGE_NOCACHE;

        page_entry = ((physaddr >> PAGE_SHIFT) & SUN4C_PFN_MASK);
        page_entry |= ((pg_iobits | _SUN4C_PAGE_PRIV) & ~(_SUN4C_PAGE_PRESENT));
        sun4c_put_pte(virt_addr, page_entry);
}

static void sun4c_mapiorange(unsigned int bus, unsigned long xpa,
    unsigned long xva, unsigned int len)
{
        while (len != 0) {
                len -= PAGE_SIZE;
                sun4c_mapioaddr(xpa, xva);
                xva += PAGE_SIZE;
                xpa += PAGE_SIZE;
        }
}

static void sun4c_unmapiorange(unsigned long virt_addr, unsigned int len)
{
        while (len != 0) {
                len -= PAGE_SIZE;
                sun4c_put_pte(virt_addr, 0);
                virt_addr += PAGE_SIZE;
        }
}

static void sun4c_alloc_context(struct mm_struct *old_mm, struct mm_struct *mm)
{
        struct ctx_list *ctxp;

        ctxp = ctx_free.next;
        if (ctxp != &ctx_free) {
                remove_from_ctx_list(ctxp);
                add_to_used_ctxlist(ctxp);
                mm->context = ctxp->ctx_number;
                ctxp->ctx_mm = mm;
                return;
        }
        ctxp = ctx_used.next;
        if (ctxp->ctx_mm == old_mm)
                ctxp = ctxp->next;
        remove_from_ctx_list(ctxp);
        add_to_used_ctxlist(ctxp);
        ctxp->ctx_mm->context = NO_CONTEXT;
        ctxp->ctx_mm = mm;
        mm->context = ctxp->ctx_number;
        sun4c_demap_context(&sun4c_context_ring[ctxp->ctx_number],
                               ctxp->ctx_number);
}

/* Switch the current MM context. */
static void sun4c_switch_mm(struct mm_struct *old_mm, struct mm_struct *mm, struct task_struct *tsk, int cpu)
{
        struct ctx_list *ctx;
        int dirty = 0;

        if (mm->context == NO_CONTEXT) {
                dirty = 1;
                sun4c_alloc_context(old_mm, mm);
        } else {
                /* Update the LRU ring of contexts. */
                ctx = ctx_list_pool + mm->context;
                remove_from_ctx_list(ctx);
                add_to_used_ctxlist(ctx);
        }
        if (dirty || old_mm != mm)
                sun4c_set_context(mm->context);
}

static void sun4c_destroy_context(struct mm_struct *mm)
{
        struct ctx_list *ctx_old;

        if (mm->context != NO_CONTEXT) {
                sun4c_demap_context(&sun4c_context_ring[mm->context], mm->context);
                ctx_old = ctx_list_pool + mm->context;
                remove_from_ctx_list(ctx_old);
                add_to_free_ctxlist(ctx_old);
                mm->context = NO_CONTEXT;
        }
}

static void sun4c_mmu_info(struct seq_file *m)
{
        int used_user_entries, i;

        used_user_entries = 0;
        for (i = 0; i < num_contexts; i++)
                used_user_entries += sun4c_context_ring[i].num_entries;

        seq_printf(m, 
                   "vacsize\t\t: %d bytes\n"
                   "vachwflush\t: %s\n"
                   "vaclinesize\t: %d bytes\n"
                   "mmuctxs\t\t: %d\n"
                   "mmupsegs\t: %d\n"
                   "kernelpsegs\t: %d\n"
                   "kfreepsegs\t: %d\n"
                   "usedpsegs\t: %d\n"
                   "ufreepsegs\t: %d\n"
                   "user_taken\t: %d\n"
                   "max_taken\t: %d\n",
                   sun4c_vacinfo.num_bytes,
                   (sun4c_vacinfo.do_hwflushes ? "yes" : "no"),
                   sun4c_vacinfo.linesize,
                   num_contexts,
                   (invalid_segment + 1),
                   sun4c_kernel_ring.num_entries,
                   sun4c_kfree_ring.num_entries,
                   used_user_entries,
                   sun4c_ufree_ring.num_entries,
                   sun4c_user_taken_entries,
                   max_user_taken_entries);
}

/* Nothing below here should touch the mmu hardware nor the mmu_entry
 * data structures.
 */

/* First the functions which the mid-level code uses to directly
 * manipulate the software page tables.  Some defines since we are
 * emulating the i386 page directory layout.
 */
#define PGD_PRESENT  0x001
#define PGD_RW       0x002
#define PGD_USER     0x004
#define PGD_ACCESSED 0x020
#define PGD_DIRTY    0x040
#define PGD_TABLE    (PGD_PRESENT | PGD_RW | PGD_USER | PGD_ACCESSED | PGD_DIRTY)

static void sun4c_set_pte(pte_t *ptep, pte_t pte)
{
        *ptep = pte;
}

static void sun4c_pgd_set(pgd_t * pgdp, pmd_t * pmdp)
{
}

static void sun4c_pmd_set(pmd_t * pmdp, pte_t * ptep)
{
        pmdp->pmdv[0] = PGD_TABLE | (unsigned long) ptep;
}

static void sun4c_pmd_populate(pmd_t * pmdp, struct page * ptep)
{
        if (page_address(ptep) == NULL) BUG();  /* No highmem on sun4c */
        pmdp->pmdv[0] = PGD_TABLE | (unsigned long) page_address(ptep);
}

static int sun4c_pte_present(pte_t pte)
{
        return ((pte_val(pte) & (_SUN4C_PAGE_PRESENT | _SUN4C_PAGE_PRIV)) != 0);
}
static void sun4c_pte_clear(pte_t *ptep)        { *ptep = __pte(0); }

static int sun4c_pmd_bad(pmd_t pmd)
{
        return (((pmd_val(pmd) & ~PAGE_MASK) != PGD_TABLE) ||
                (!virt_addr_valid(pmd_val(pmd))));
}

static int sun4c_pmd_present(pmd_t pmd)
{
        return ((pmd_val(pmd) & PGD_PRESENT) != 0);
}

#if 0 /* if PMD takes one word */
static void sun4c_pmd_clear(pmd_t *pmdp)        { *pmdp = __pmd(0); }
#else /* if pmd_t is a longish aggregate */
static void sun4c_pmd_clear(pmd_t *pmdp) {
        memset((void *)pmdp, 0, sizeof(pmd_t));
}
#endif

static int sun4c_pgd_none(pgd_t pgd)            { return 0; }
static int sun4c_pgd_bad(pgd_t pgd)             { return 0; }
static int sun4c_pgd_present(pgd_t pgd)         { return 1; }
static void sun4c_pgd_clear(pgd_t * pgdp)       { }

/*
 * The following only work if pte_present() is true.
 * Undefined behaviour if not..
 */
static pte_t sun4c_pte_mkwrite(pte_t pte)
{
        pte = __pte(pte_val(pte) | _SUN4C_PAGE_WRITE);
        if (pte_val(pte) & _SUN4C_PAGE_MODIFIED)
                pte = __pte(pte_val(pte) | _SUN4C_PAGE_SILENT_WRITE);
        return pte;
}

static pte_t sun4c_pte_mkdirty(pte_t pte)
{
        pte = __pte(pte_val(pte) | _SUN4C_PAGE_MODIFIED);
        if (pte_val(pte) & _SUN4C_PAGE_WRITE)
                pte = __pte(pte_val(pte) | _SUN4C_PAGE_SILENT_WRITE);
        return pte;
}

static pte_t sun4c_pte_mkyoung(pte_t pte)
{
        pte = __pte(pte_val(pte) | _SUN4C_PAGE_ACCESSED);
        if (pte_val(pte) & _SUN4C_PAGE_READ)
                pte = __pte(pte_val(pte) | _SUN4C_PAGE_SILENT_READ);
        return pte;
}

/*
 * Conversion functions: convert a page and protection to a page entry,
 * and a page entry and page directory to the page they refer to.
 */
static pte_t sun4c_mk_pte(struct page *page, pgprot_t pgprot)
{
        return __pte(page_to_pfn(page) | pgprot_val(pgprot));
}

static pte_t sun4c_mk_pte_phys(unsigned long phys_page, pgprot_t pgprot)
{
        return __pte((phys_page >> PAGE_SHIFT) | pgprot_val(pgprot));
}

static pte_t sun4c_mk_pte_io(unsigned long page, pgprot_t pgprot, int space)
{
        return __pte(((page - PAGE_OFFSET) >> PAGE_SHIFT) | pgprot_val(pgprot));
}

static unsigned long sun4c_pte_pfn(pte_t pte)
{
        return pte_val(pte) & SUN4C_PFN_MASK;
}

static pte_t sun4c_pgoff_to_pte(unsigned long pgoff)
{
        return __pte(pgoff | _SUN4C_PAGE_FILE);
}

static unsigned long sun4c_pte_to_pgoff(pte_t pte)
{
        return pte_val(pte) & ((1UL << PTE_FILE_MAX_BITS) - 1);
}


static inline unsigned long sun4c_pmd_page_v(pmd_t pmd)
{
        return (pmd_val(pmd) & PAGE_MASK);
}

static struct page *sun4c_pmd_page(pmd_t pmd)
{
        return virt_to_page(sun4c_pmd_page_v(pmd));
}

static unsigned long sun4c_pgd_page(pgd_t pgd) { return 0; }

/* to find an entry in a page-table-directory */
static inline pgd_t *sun4c_pgd_offset(struct mm_struct * mm, unsigned long address)
{
        return mm->pgd + (address >> SUN4C_PGDIR_SHIFT);
}

/* Find an entry in the second-level page table.. */
static pmd_t *sun4c_pmd_offset(pgd_t * dir, unsigned long address)
{
        return (pmd_t *) dir;
}

/* Find an entry in the third-level page table.. */ 
pte_t *sun4c_pte_offset_kernel(pmd_t * dir, unsigned long address)
{
        return (pte_t *) sun4c_pmd_page_v(*dir) +
                        ((address >> PAGE_SHIFT) & (SUN4C_PTRS_PER_PTE - 1));
}

static unsigned long sun4c_swp_type(swp_entry_t entry)
{
        return (entry.val & SUN4C_SWP_TYPE_MASK);
}

static unsigned long sun4c_swp_offset(swp_entry_t entry)
{
        return (entry.val >> SUN4C_SWP_OFF_SHIFT) & SUN4C_SWP_OFF_MASK;
}

static swp_entry_t sun4c_swp_entry(unsigned long type, unsigned long offset)
{
        return (swp_entry_t) {
                  (offset & SUN4C_SWP_OFF_MASK) << SUN4C_SWP_OFF_SHIFT
                | (type & SUN4C_SWP_TYPE_MASK) };
}

static void sun4c_free_pte_slow(pte_t *pte)
{
        free_page((unsigned long)pte);
}

static void sun4c_free_pgd_slow(pgd_t *pgd)
{
        free_page((unsigned long)pgd);
}

static pgd_t *sun4c_get_pgd_fast(void)
{
        unsigned long *ret;

        if ((ret = pgd_quicklist) != NULL) {
                pgd_quicklist = (unsigned long *)(*ret);
                ret[0] = ret[1];
                pgtable_cache_size--;
        } else {
                pgd_t *init;
                
                ret = (unsigned long *)__get_free_page(GFP_KERNEL);
                memset (ret, 0, (KERNBASE / SUN4C_PGDIR_SIZE) * sizeof(pgd_t));
                init = sun4c_pgd_offset(&init_mm, 0);
                memcpy (((pgd_t *)ret) + USER_PTRS_PER_PGD, init + USER_PTRS_PER_PGD,
                        (PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t));
        }
        return (pgd_t *)ret;
}

static void sun4c_free_pgd_fast(pgd_t *pgd)
{
        *(unsigned long *)pgd = (unsigned long) pgd_quicklist;
        pgd_quicklist = (unsigned long *) pgd;
        pgtable_cache_size++;
}


static inline pte_t *
sun4c_pte_alloc_one_fast(struct mm_struct *mm, unsigned long address)
{
        unsigned long *ret;

        if ((ret = (unsigned long *)pte_quicklist) != NULL) {
                pte_quicklist = (unsigned long *)(*ret);
                ret[0] = ret[1];
                pgtable_cache_size--;
        }
        return (pte_t *)ret;
}

static pte_t *sun4c_pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
{
        pte_t *pte;

        if ((pte = sun4c_pte_alloc_one_fast(mm, address)) != NULL)
                return pte;

        pte = (pte_t *)get_zeroed_page(GFP_KERNEL|__GFP_REPEAT);
        return pte;
}

static pgtable_t sun4c_pte_alloc_one(struct mm_struct *mm, unsigned long address)
{
        pte_t *pte;
        struct page *page;

        pte = sun4c_pte_alloc_one_kernel(mm, address);
        if (pte == NULL)
                return NULL;
        page = virt_to_page(pte);
        pgtable_page_ctor(page);
        return page;
}

static inline void sun4c_free_pte_fast(pte_t *pte)
{
        *(unsigned long *)pte = (unsigned long) pte_quicklist;
        pte_quicklist = (unsigned long *) pte;
        pgtable_cache_size++;
}

static void sun4c_pte_free(pgtable_t pte)
{
        pgtable_page_dtor(pte);
        sun4c_free_pte_fast(page_address(pte));
}

/*
 * allocating and freeing a pmd is trivial: the 1-entry pmd is
 * inside the pgd, so has no extra memory associated with it.
 */
static pmd_t *sun4c_pmd_alloc_one(struct mm_struct *mm, unsigned long address)
{
        BUG();
        return NULL;
}

static void sun4c_free_pmd_fast(pmd_t * pmd) { }

static void sun4c_check_pgt_cache(int low, int high)
{
        if (pgtable_cache_size > high) {
                do {
                        if (pgd_quicklist)
                                sun4c_free_pgd_slow(sun4c_get_pgd_fast());
                        if (pte_quicklist)
                                sun4c_free_pte_slow(sun4c_pte_alloc_one_fast(NULL, 0));
                } while (pgtable_cache_size > low);
        }
}

/* An experiment, turn off by default for now... -DaveM */
#define SUN4C_PRELOAD_PSEG

void sun4c_update_mmu_cache(struct vm_area_struct *vma, unsigned long address, pte_t pte)
{
        unsigned long flags;
        int pseg;

        if (vma->vm_mm->context == NO_CONTEXT)
                return;

        local_irq_save(flags);
        address &= PAGE_MASK;
        if ((pseg = sun4c_get_segmap(address)) == invalid_segment) {
                struct sun4c_mmu_entry *entry = sun4c_user_strategy();
                struct mm_struct *mm = vma->vm_mm;
                unsigned long start, end;

                entry->vaddr = start = (address & SUN4C_REAL_PGDIR_MASK);
                entry->ctx = mm->context;
                add_ring_ordered(sun4c_context_ring + mm->context, entry);
                sun4c_put_segmap(entry->vaddr, entry->pseg);
                end = start + SUN4C_REAL_PGDIR_SIZE;
                while (start < end) {
#ifdef SUN4C_PRELOAD_PSEG
                        pgd_t *pgdp = sun4c_pgd_offset(mm, start);
                        pte_t *ptep;

                        if (!pgdp)
                                goto no_mapping;
                        ptep = sun4c_pte_offset_kernel((pmd_t *) pgdp, start);
                        if (!ptep || !(pte_val(*ptep) & _SUN4C_PAGE_PRESENT))
                                goto no_mapping;
                        sun4c_put_pte(start, pte_val(*ptep));
                        goto next;

                no_mapping:
#endif
                        sun4c_put_pte(start, 0);
#ifdef SUN4C_PRELOAD_PSEG
                next:
#endif
                        start += PAGE_SIZE;
                }
#ifndef SUN4C_PRELOAD_PSEG
                sun4c_put_pte(address, pte_val(pte));
#endif
                local_irq_restore(flags);
                return;
        } else {
                struct sun4c_mmu_entry *entry = &mmu_entry_pool[pseg];

                remove_lru(entry);
                add_lru(entry);
        }

        sun4c_put_pte(address, pte_val(pte));
        local_irq_restore(flags);
}

extern void sparc_context_init(int);
extern unsigned long bootmem_init(unsigned long *pages_avail);
extern unsigned long last_valid_pfn;

void __init sun4c_paging_init(void)
{
        int i, cnt;
        unsigned long kernel_end, vaddr;
        extern struct resource sparc_iomap;
        unsigned long end_pfn, pages_avail;

        kernel_end = (unsigned long) &_end;
        kernel_end = SUN4C_REAL_PGDIR_ALIGN(kernel_end);

        pages_avail = 0;
        last_valid_pfn = bootmem_init(&pages_avail);
        end_pfn = last_valid_pfn;

        sun4c_probe_mmu();
        invalid_segment = (num_segmaps - 1);
        sun4c_init_mmu_entry_pool();
        sun4c_init_rings();
        sun4c_init_map_kernelprom(kernel_end);
        sun4c_init_clean_mmu(kernel_end);
        sun4c_init_fill_kernel_ring(SUN4C_KERNEL_BUCKETS);
        sun4c_init_lock_area(sparc_iomap.start, IOBASE_END);
        sun4c_init_lock_area(DVMA_VADDR, DVMA_END);
        sun4c_init_lock_areas();
        sun4c_init_fill_user_ring();

        sun4c_set_context(0);
        memset(swapper_pg_dir, 0, PAGE_SIZE);
        memset(pg0, 0, PAGE_SIZE);
        memset(pg1, 0, PAGE_SIZE);
        memset(pg2, 0, PAGE_SIZE);
        memset(pg3, 0, PAGE_SIZE);

        /* Save work later. */
        vaddr = VMALLOC_START;
        swapper_pg_dir[vaddr>>SUN4C_PGDIR_SHIFT] = __pgd(PGD_TABLE | (unsigned long) pg0);
        vaddr += SUN4C_PGDIR_SIZE;
        swapper_pg_dir[vaddr>>SUN4C_PGDIR_SHIFT] = __pgd(PGD_TABLE | (unsigned long) pg1);
        vaddr += SUN4C_PGDIR_SIZE;
        swapper_pg_dir[vaddr>>SUN4C_PGDIR_SHIFT] = __pgd(PGD_TABLE | (unsigned long) pg2);
        vaddr += SUN4C_PGDIR_SIZE;
        swapper_pg_dir[vaddr>>SUN4C_PGDIR_SHIFT] = __pgd(PGD_TABLE | (unsigned long) pg3);
        sun4c_init_ss2_cache_bug();
        sparc_context_init(num_contexts);

        {
                unsigned long zones_size[MAX_NR_ZONES];
                unsigned long zholes_size[MAX_NR_ZONES];
                unsigned long npages;
                int znum;

                for (znum = 0; znum < MAX_NR_ZONES; znum++)
                        zones_size[znum] = zholes_size[znum] = 0;

                npages = max_low_pfn - pfn_base;

                zones_size[ZONE_DMA] = npages;
                zholes_size[ZONE_DMA] = npages - pages_avail;

                npages = highend_pfn - max_low_pfn;
                zones_size[ZONE_HIGHMEM] = npages;
                zholes_size[ZONE_HIGHMEM] = npages - calc_highpages();

                free_area_init_node(0, zones_size, pfn_base, zholes_size);
        }

        cnt = 0;
        for (i = 0; i < num_segmaps; i++)
                if (mmu_entry_pool[i].locked)
                        cnt++;

        max_user_taken_entries = num_segmaps - cnt - 40 - 1;

        printk("SUN4C: %d mmu entries for the kernel\n", cnt);
}

static pgprot_t sun4c_pgprot_noncached(pgprot_t prot)
{
        prot |= __pgprot(_SUN4C_PAGE_IO | _SUN4C_PAGE_NOCACHE);

        return prot;
}

/* Load up routines and constants for sun4c mmu */
void __init ld_mmu_sun4c(void)
{
        extern void ___xchg32_sun4c(void);
        
        printk("Loading sun4c MMU routines\n");

        /* First the constants */
        BTFIXUPSET_SIMM13(pgdir_shift, SUN4C_PGDIR_SHIFT);
        BTFIXUPSET_SETHI(pgdir_size, SUN4C_PGDIR_SIZE);
        BTFIXUPSET_SETHI(pgdir_mask, SUN4C_PGDIR_MASK);

        BTFIXUPSET_SIMM13(ptrs_per_pmd, SUN4C_PTRS_PER_PMD);
        BTFIXUPSET_SIMM13(ptrs_per_pgd, SUN4C_PTRS_PER_PGD);
        BTFIXUPSET_SIMM13(user_ptrs_per_pgd, KERNBASE / SUN4C_PGDIR_SIZE);

        BTFIXUPSET_INT(page_none, pgprot_val(SUN4C_PAGE_NONE));
        PAGE_SHARED = pgprot_val(SUN4C_PAGE_SHARED);
        BTFIXUPSET_INT(page_copy, pgprot_val(SUN4C_PAGE_COPY));
        BTFIXUPSET_INT(page_readonly, pgprot_val(SUN4C_PAGE_READONLY));
        BTFIXUPSET_INT(page_kernel, pgprot_val(SUN4C_PAGE_KERNEL));
        page_kernel = pgprot_val(SUN4C_PAGE_KERNEL);

        /* Functions */
        BTFIXUPSET_CALL(pgprot_noncached, sun4c_pgprot_noncached, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(___xchg32, ___xchg32_sun4c, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(do_check_pgt_cache, sun4c_check_pgt_cache, BTFIXUPCALL_NORM);
        
        BTFIXUPSET_CALL(flush_cache_all, sun4c_flush_cache_all, BTFIXUPCALL_NORM);

        if (sun4c_vacinfo.do_hwflushes) {
                BTFIXUPSET_CALL(sun4c_flush_page, sun4c_flush_page_hw, BTFIXUPCALL_NORM);
                BTFIXUPSET_CALL(sun4c_flush_segment, sun4c_flush_segment_hw, BTFIXUPCALL_NORM);
                BTFIXUPSET_CALL(sun4c_flush_context, sun4c_flush_context_hw, BTFIXUPCALL_NORM);
        } else {
                BTFIXUPSET_CALL(sun4c_flush_page, sun4c_flush_page_sw, BTFIXUPCALL_NORM);
                BTFIXUPSET_CALL(sun4c_flush_segment, sun4c_flush_segment_sw, BTFIXUPCALL_NORM);
                BTFIXUPSET_CALL(sun4c_flush_context, sun4c_flush_context_sw, BTFIXUPCALL_NORM);
        }

        BTFIXUPSET_CALL(flush_tlb_mm, sun4c_flush_tlb_mm, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(flush_cache_mm, sun4c_flush_cache_mm, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(destroy_context, sun4c_destroy_context, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(switch_mm, sun4c_switch_mm, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(flush_cache_page, sun4c_flush_cache_page, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(flush_tlb_page, sun4c_flush_tlb_page, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(flush_tlb_range, sun4c_flush_tlb_range, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(flush_cache_range, sun4c_flush_cache_range, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(__flush_page_to_ram, sun4c_flush_page_to_ram, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(flush_tlb_all, sun4c_flush_tlb_all, BTFIXUPCALL_NORM);

        BTFIXUPSET_CALL(flush_sig_insns, sun4c_flush_sig_insns, BTFIXUPCALL_NOP);

        BTFIXUPSET_CALL(set_pte, sun4c_set_pte, BTFIXUPCALL_STO1O0);

        /* The 2.4.18 code does not set this on sun4c, how does it work? XXX */
        /* BTFIXUPSET_SETHI(none_mask, 0x00000000); */  /* Defaults to zero? */

        BTFIXUPSET_CALL(pte_pfn, sun4c_pte_pfn, BTFIXUPCALL_NORM);
#if 0 /* PAGE_SHIFT <= 12 */ /* Eek. Investigate. XXX */
        BTFIXUPSET_CALL(pmd_page, sun4c_pmd_page, BTFIXUPCALL_ANDNINT(PAGE_SIZE - 1));
#else
        BTFIXUPSET_CALL(pmd_page, sun4c_pmd_page, BTFIXUPCALL_NORM);
#endif
        BTFIXUPSET_CALL(pmd_set, sun4c_pmd_set, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(pmd_populate, sun4c_pmd_populate, BTFIXUPCALL_NORM);

        BTFIXUPSET_CALL(pte_present, sun4c_pte_present, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(pte_clear, sun4c_pte_clear, BTFIXUPCALL_STG0O0);

        BTFIXUPSET_CALL(pmd_bad, sun4c_pmd_bad, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(pmd_present, sun4c_pmd_present, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(pmd_clear, sun4c_pmd_clear, BTFIXUPCALL_STG0O0);

        BTFIXUPSET_CALL(pgd_none, sun4c_pgd_none, BTFIXUPCALL_RETINT(0));
        BTFIXUPSET_CALL(pgd_bad, sun4c_pgd_bad, BTFIXUPCALL_RETINT(0));
        BTFIXUPSET_CALL(pgd_present, sun4c_pgd_present, BTFIXUPCALL_RETINT(1));
        BTFIXUPSET_CALL(pgd_clear, sun4c_pgd_clear, BTFIXUPCALL_NOP);

        BTFIXUPSET_CALL(mk_pte, sun4c_mk_pte, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(mk_pte_phys, sun4c_mk_pte_phys, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(mk_pte_io, sun4c_mk_pte_io, BTFIXUPCALL_NORM);

        BTFIXUPSET_INT(pte_modify_mask, _SUN4C_PAGE_CHG_MASK);
        BTFIXUPSET_CALL(pmd_offset, sun4c_pmd_offset, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(pte_offset_kernel, sun4c_pte_offset_kernel, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(free_pte_fast, sun4c_free_pte_fast, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(pte_free, sun4c_pte_free, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(pte_alloc_one_kernel, sun4c_pte_alloc_one_kernel, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(pte_alloc_one, sun4c_pte_alloc_one, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(free_pmd_fast, sun4c_free_pmd_fast, BTFIXUPCALL_NOP);
        BTFIXUPSET_CALL(pmd_alloc_one, sun4c_pmd_alloc_one, BTFIXUPCALL_RETO0);
        BTFIXUPSET_CALL(free_pgd_fast, sun4c_free_pgd_fast, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(get_pgd_fast, sun4c_get_pgd_fast, BTFIXUPCALL_NORM);

        BTFIXUPSET_HALF(pte_writei, _SUN4C_PAGE_WRITE);
        BTFIXUPSET_HALF(pte_dirtyi, _SUN4C_PAGE_MODIFIED);
        BTFIXUPSET_HALF(pte_youngi, _SUN4C_PAGE_ACCESSED);
        BTFIXUPSET_HALF(pte_filei, _SUN4C_PAGE_FILE);
        BTFIXUPSET_HALF(pte_wrprotecti, _SUN4C_PAGE_WRITE|_SUN4C_PAGE_SILENT_WRITE);
        BTFIXUPSET_HALF(pte_mkcleani, _SUN4C_PAGE_MODIFIED|_SUN4C_PAGE_SILENT_WRITE);
        BTFIXUPSET_HALF(pte_mkoldi, _SUN4C_PAGE_ACCESSED|_SUN4C_PAGE_SILENT_READ);
        BTFIXUPSET_CALL(pte_mkwrite, sun4c_pte_mkwrite, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(pte_mkdirty, sun4c_pte_mkdirty, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(pte_mkyoung, sun4c_pte_mkyoung, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(update_mmu_cache, sun4c_update_mmu_cache, BTFIXUPCALL_NORM);

        BTFIXUPSET_CALL(pte_to_pgoff, sun4c_pte_to_pgoff, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(pgoff_to_pte, sun4c_pgoff_to_pte, BTFIXUPCALL_NORM);

        BTFIXUPSET_CALL(mmu_lockarea, sun4c_lockarea, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(mmu_unlockarea, sun4c_unlockarea, BTFIXUPCALL_NORM);

        BTFIXUPSET_CALL(mmu_get_scsi_one, sun4c_get_scsi_one, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(mmu_get_scsi_sgl, sun4c_get_scsi_sgl, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(mmu_release_scsi_one, sun4c_release_scsi_one, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(mmu_release_scsi_sgl, sun4c_release_scsi_sgl, BTFIXUPCALL_NORM);

        BTFIXUPSET_CALL(mmu_map_dma_area, sun4c_map_dma_area, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(mmu_unmap_dma_area, sun4c_unmap_dma_area, BTFIXUPCALL_NORM);

        BTFIXUPSET_CALL(sparc_mapiorange, sun4c_mapiorange, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(sparc_unmapiorange, sun4c_unmapiorange, BTFIXUPCALL_NORM);

        BTFIXUPSET_CALL(__swp_type, sun4c_swp_type, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(__swp_offset, sun4c_swp_offset, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(__swp_entry, sun4c_swp_entry, BTFIXUPCALL_NORM);

        BTFIXUPSET_CALL(alloc_thread_info, sun4c_alloc_thread_info, BTFIXUPCALL_NORM);
        BTFIXUPSET_CALL(free_thread_info, sun4c_free_thread_info, BTFIXUPCALL_NORM);

        BTFIXUPSET_CALL(mmu_info, sun4c_mmu_info, BTFIXUPCALL_NORM);

        /* These should _never_ get called with two level tables. */
        BTFIXUPSET_CALL(pgd_set, sun4c_pgd_set, BTFIXUPCALL_NOP);
        BTFIXUPSET_CALL(pgd_page_vaddr, sun4c_pgd_page, BTFIXUPCALL_RETO0);
}