arch/mips/kernel/r4k_switch.S

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 1994, 1995, 1996, 1998, 1999, 2002, 2003 Ralf Baechle
   7  * Copyright (C) 1996 David S. Miller (davem@davemloft.net)
   8  * Copyright (C) 1994, 1995, 1996, by Andreas Busse
   9  * Copyright (C) 1999 Silicon Graphics, Inc.
  10  * Copyright (C) 2000 MIPS Technologies, Inc.
  11  *    written by Carsten Langgaard, carstenl@mips.com
  12  */
  13 #include <asm/asm.h>
  14 #include <asm/cachectl.h>
  15 #include <asm/fpregdef.h>
  16 #include <asm/mipsregs.h>
  17 #include <asm/asm-offsets.h>
  18 #include <asm/pgtable-bits.h>
  19 #include <asm/regdef.h>
  20 #include <asm/stackframe.h>
  21 #include <asm/thread_info.h>
  22
  23 #include <asm/asmmacro.h>
  24
  25 /*
  26  * Offset to the current process status flags, the first 32 bytes of the
  27  * stack are not used.
  28  */
  29 #define ST_OFF (_THREAD_SIZE - 32 - PT_SIZE + PT_STATUS)
  30
  31 /*
  32  * FPU context is saved iff the process has used it's FPU in the current
  33  * time slice as indicated by _TIF_USEDFPU.  In any case, the CU1 bit for user
  34  * space STATUS register should be 0, so that a process *always* starts its
  35  * userland with FPU disabled after each context switch.
  36  *
  37  * FPU will be enabled as soon as the process accesses FPU again, through
  38  * do_cpu() trap.
  39  */
  40
  41 /*
  42  * task_struct *resume(task_struct *prev, task_struct *next,
  43  *                     struct thread_info *next_ti, int usedfpu)
  44  */
  45         .align  5
  46         LEAF(resume)
  47         mfc0    t1, CP0_STATUS
  48         LONG_S  t1, THREAD_STATUS(a0)
  49         cpu_save_nonscratch a0
  50         LONG_S  ra, THREAD_REG31(a0)
  51
  52         /*
  53          * check if we need to save FPU registers
  54          */
  55
  56         beqz    a3, 1f
  57
  58         PTR_L   t3, TASK_THREAD_INFO(a0)
  59         /*
  60          * clear saved user stack CU1 bit
  61          */
  62         LONG_L  t0, ST_OFF(t3)
  63         li      t1, ~ST0_CU1
  64         and     t0, t0, t1
  65         LONG_S  t0, ST_OFF(t3)
  66
  67         fpu_save_double a0 t0 t1                # c0_status passed in t0
  68                                                 # clobbers t1
  69 1:
  70
  71         /*
  72          * The order of restoring the registers takes care of the race
  73          * updating $28, $29 and kernelsp without disabling ints.
  74          */
  75         move    $28, a2
  76         cpu_restore_nonscratch a1
  77
  78         PTR_ADDU        t0, $28, _THREAD_SIZE - 32
  79         set_saved_sp    t0, t1, t2
  80 #ifdef CONFIG_MIPS_MT_SMTC
  81         /* Read-modify-writes of Status must be atomic on a VPE */
  82         mfc0    t2, CP0_TCSTATUS
  83         ori     t1, t2, TCSTATUS_IXMT
  84         mtc0    t1, CP0_TCSTATUS
  85         andi    t2, t2, TCSTATUS_IXMT
  86         _ehb
  87         DMT     8                               # dmt   t0
  88         move    t1,ra
  89         jal     mips_ihb
  90         move    ra,t1
  91 #endif /* CONFIG_MIPS_MT_SMTC */
  92         mfc0    t1, CP0_STATUS          /* Do we really need this? */
  93         li      a3, 0xff01
  94         and     t1, a3
  95         LONG_L  a2, THREAD_STATUS(a1)
  96         nor     a3, $0, a3
  97         and     a2, a3
  98         or      a2, t1
  99         mtc0    a2, CP0_STATUS
 100 #ifdef CONFIG_MIPS_MT_SMTC
 101         _ehb
 102         andi    t0, t0, VPECONTROL_TE
 103         beqz    t0, 1f
 104         emt
 105 1:
 106         mfc0    t1, CP0_TCSTATUS
 107         xori    t1, t1, TCSTATUS_IXMT
 108         or      t1, t1, t2
 109         mtc0    t1, CP0_TCSTATUS
 110         _ehb
 111 #endif /* CONFIG_MIPS_MT_SMTC */
 112         move    v0, a0
 113         jr      ra
 114         END(resume)
 115
 116 /*
 117  * Save a thread's fp context.
 118  */
 119 LEAF(_save_fp)
 120 #ifdef CONFIG_64BIT
 121         mfc0    t0, CP0_STATUS
 122 #endif
 123         fpu_save_double a0 t0 t1                # clobbers t1
 124         jr      ra
 125         END(_save_fp)
 126
 127 /*
 128  * Restore a thread's fp context.
 129  */
 130 LEAF(_restore_fp)
 131 #ifdef CONFIG_64BIT
 132         mfc0    t0, CP0_STATUS
 133 #endif
 134         fpu_restore_double a0 t0 t1             # clobbers t1
 135         jr      ra
 136         END(_restore_fp)
 137
 138 /*
 139  * Load the FPU with signalling NANS.  This bit pattern we're using has
 140  * the property that no matter whether considered as single or as double
 141  * precision represents signaling NANS.
 142  *
 143  * We initialize fcr31 to rounding to nearest, no exceptions.
 144  */
 145
 146 #define FPU_DEFAULT  0x00000000
 147
 148 LEAF(_init_fpu)
 149 #ifdef CONFIG_MIPS_MT_SMTC
 150         /* Rather than manipulate per-VPE Status, set per-TC bit in TCStatus */
 151         mfc0    t0, CP0_TCSTATUS
 152         /* Bit position is the same for Status, TCStatus */
 153         li      t1, ST0_CU1
 154         or      t0, t1
 155         mtc0    t0, CP0_TCSTATUS
 156 #else /* Normal MIPS CU1 enable */
 157         mfc0    t0, CP0_STATUS
 158         li      t1, ST0_CU1
 159         or      t0, t1
 160         mtc0    t0, CP0_STATUS
 161 #endif /* CONFIG_MIPS_MT_SMTC */
 162         enable_fpu_hazard
 163
 164         li      t1, FPU_DEFAULT
 165         ctc1    t1, fcr31
 166
 167         li      t1, -1                          # SNaN
 168
 169 #ifdef CONFIG_64BIT
 170         sll     t0, t0, 5
 171         bgez    t0, 1f                          # 16 / 32 register mode?
 172
 173         dmtc1   t1, $f1
 174         dmtc1   t1, $f3
 175         dmtc1   t1, $f5
 176         dmtc1   t1, $f7
 177         dmtc1   t1, $f9
 178         dmtc1   t1, $f11
 179         dmtc1   t1, $f13
 180         dmtc1   t1, $f15
 181         dmtc1   t1, $f17
 182         dmtc1   t1, $f19
 183         dmtc1   t1, $f21
 184         dmtc1   t1, $f23
 185         dmtc1   t1, $f25
 186         dmtc1   t1, $f27
 187         dmtc1   t1, $f29
 188         dmtc1   t1, $f31
 189 1:
 190 #endif
 191
 192 #ifdef CONFIG_CPU_MIPS32
 193         mtc1    t1, $f0
 194         mtc1    t1, $f1
 195         mtc1    t1, $f2
 196         mtc1    t1, $f3
 197         mtc1    t1, $f4
 198         mtc1    t1, $f5
 199         mtc1    t1, $f6
 200         mtc1    t1, $f7
 201         mtc1    t1, $f8
 202         mtc1    t1, $f9
 203         mtc1    t1, $f10
 204         mtc1    t1, $f11
 205         mtc1    t1, $f12
 206         mtc1    t1, $f13
 207         mtc1    t1, $f14
 208         mtc1    t1, $f15
 209         mtc1    t1, $f16
 210         mtc1    t1, $f17
 211         mtc1    t1, $f18
 212         mtc1    t1, $f19
 213         mtc1    t1, $f20
 214         mtc1    t1, $f21
 215         mtc1    t1, $f22
 216         mtc1    t1, $f23
 217         mtc1    t1, $f24
 218         mtc1    t1, $f25
 219         mtc1    t1, $f26
 220         mtc1    t1, $f27
 221         mtc1    t1, $f28
 222         mtc1    t1, $f29
 223         mtc1    t1, $f30
 224         mtc1    t1, $f31
 225 #else
 226         .set    mips3
 227         dmtc1   t1, $f0
 228         dmtc1   t1, $f2
 229         dmtc1   t1, $f4
 230         dmtc1   t1, $f6
 231         dmtc1   t1, $f8
 232         dmtc1   t1, $f10
 233         dmtc1   t1, $f12
 234         dmtc1   t1, $f14
 235         dmtc1   t1, $f16
 236         dmtc1   t1, $f18
 237         dmtc1   t1, $f20
 238         dmtc1   t1, $f22
 239         dmtc1   t1, $f24
 240         dmtc1   t1, $f26
 241         dmtc1   t1, $f28
 242         dmtc1   t1, $f30
 243 #endif
 244         jr      ra
 245         END(_init_fpu)