arch/x86/kernel/apb_timer.c

   1 /*
   2  * apb_timer.c: Driver for Langwell APB timers
   3  *
   4  * (C) Copyright 2009 Intel Corporation
   5  * Author: Jacob Pan (jacob.jun.pan@intel.com)
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; version 2
  10  * of the License.
  11  *
  12  * Note:
  13  * Langwell is the south complex of Intel Moorestown MID platform. There are
  14  * eight external timers in total that can be used by the operating system.
  15  * The timer information, such as frequency and addresses, is provided to the
  16  * OS via SFI tables.
  17  * Timer interrupts are routed via FW/HW emulated IOAPIC independently via
  18  * individual redirection table entries (RTE).
  19  * Unlike HPET, there is no master counter, therefore one of the timers are
  20  * used as clocksource. The overall allocation looks like:
  21  *  - timer 0 - NR_CPUs for per cpu timer
  22  *  - one timer for clocksource
  23  *  - one timer for watchdog driver.
  24  * It is also worth notice that APB timer does not support true one-shot mode,
  25  * free-running mode will be used here to emulate one-shot mode.
  26  * APB timer can also be used as broadcast timer along with per cpu local APIC
  27  * timer, but by default APB timer has higher rating than local APIC timers.
  28  */
  29
  30 #include <linux/delay.h>
  31 #include <linux/dw_apb_timer.h>
  32 #include <linux/errno.h>
  33 #include <linux/init.h>
  34 #include <linux/slab.h>
  35 #include <linux/pm.h>
  36 #include <linux/sfi.h>
  37 #include <linux/interrupt.h>
  38 #include <linux/cpu.h>
  39 #include <linux/irq.h>
  40
  41 #include <asm/fixmap.h>
  42 #include <asm/apb_timer.h>
  43 #include <asm/intel-mid.h>
  44 #include <asm/time.h>
  45
  46 #define APBT_CLOCKEVENT_RATING          110
  47 #define APBT_CLOCKSOURCE_RATING         250
  48
  49 #define APBT_CLOCKEVENT0_NUM   (0)
  50 #define APBT_CLOCKSOURCE_NUM   (2)
  51
  52 static phys_addr_t apbt_address;
  53 static int apb_timer_block_enabled;
  54 static void __iomem *apbt_virt_address;
  55
  56 /*
  57  * Common DW APB timer info
  58  */
  59 static unsigned long apbt_freq;
  60
  61 struct apbt_dev {
  62         struct dw_apb_clock_event_device        *timer;
  63         unsigned int                            num;
  64         int                                     cpu;
  65         unsigned int                            irq;
  66         char                                    name[10];
  67 };
  68
  69 static struct dw_apb_clocksource *clocksource_apbt;
  70
  71 static inline void __iomem *adev_virt_addr(struct apbt_dev *adev)
  72 {
  73         return apbt_virt_address + adev->num * APBTMRS_REG_SIZE;
  74 }
  75
  76 static DEFINE_PER_CPU(struct apbt_dev, cpu_apbt_dev);
  77
  78 #ifdef CONFIG_SMP
  79 static unsigned int apbt_num_timers_used;
  80 #endif
  81
  82 static inline void apbt_set_mapping(void)
  83 {
  84         struct sfi_timer_table_entry *mtmr;
  85         int phy_cs_timer_id = 0;
  86
  87         if (apbt_virt_address) {
  88                 pr_debug("APBT base already mapped\n");
  89                 return;
  90         }
  91         mtmr = sfi_get_mtmr(APBT_CLOCKEVENT0_NUM);
  92         if (mtmr == NULL) {
  93                 printk(KERN_ERR "Failed to get MTMR %d from SFI\n",
  94                        APBT_CLOCKEVENT0_NUM);
  95                 return;
  96         }
  97         apbt_address = (phys_addr_t)mtmr->phys_addr;
  98         if (!apbt_address) {
  99                 printk(KERN_WARNING "No timer base from SFI, use default\n");
 100                 apbt_address = APBT_DEFAULT_BASE;
 101         }
 102         apbt_virt_address = ioremap_nocache(apbt_address, APBT_MMAP_SIZE);
 103         if (!apbt_virt_address) {
 104                 pr_debug("Failed mapping APBT phy address at %lu\n",\
 105                          (unsigned long)apbt_address);
 106                 goto panic_noapbt;
 107         }
 108         apbt_freq = mtmr->freq_hz;
 109         sfi_free_mtmr(mtmr);
 110
 111         /* Now figure out the physical timer id for clocksource device */
 112         mtmr = sfi_get_mtmr(APBT_CLOCKSOURCE_NUM);
 113         if (mtmr == NULL)
 114                 goto panic_noapbt;
 115
 116         /* Now figure out the physical timer id */
 117         pr_debug("Use timer %d for clocksource\n",
 118                  (int)(mtmr->phys_addr & 0xff) / APBTMRS_REG_SIZE);
 119         phy_cs_timer_id = (unsigned int)(mtmr->phys_addr & 0xff) /
 120                 APBTMRS_REG_SIZE;
 121
 122         clocksource_apbt = dw_apb_clocksource_init(APBT_CLOCKSOURCE_RATING,
 123                 "apbt0", apbt_virt_address + phy_cs_timer_id *
 124                 APBTMRS_REG_SIZE, apbt_freq);
 125         return;
 126
 127 panic_noapbt:
 128         panic("Failed to setup APB system timer\n");
 129
 130 }
 131
 132 static inline void apbt_clear_mapping(void)
 133 {
 134         iounmap(apbt_virt_address);
 135         apbt_virt_address = NULL;
 136 }
 137
 138 static int __init apbt_clockevent_register(void)
 139 {
 140         struct sfi_timer_table_entry *mtmr;
 141         struct apbt_dev *adev = this_cpu_ptr(&cpu_apbt_dev);
 142
 143         mtmr = sfi_get_mtmr(APBT_CLOCKEVENT0_NUM);
 144         if (mtmr == NULL) {
 145                 printk(KERN_ERR "Failed to get MTMR %d from SFI\n",
 146                        APBT_CLOCKEVENT0_NUM);
 147                 return -ENODEV;
 148         }
 149
 150         adev->num = smp_processor_id();
 151         adev->timer = dw_apb_clockevent_init(smp_processor_id(), "apbt0",
 152                 intel_mid_timer_options == INTEL_MID_TIMER_LAPIC_APBT ?
 153                 APBT_CLOCKEVENT_RATING - 100 : APBT_CLOCKEVENT_RATING,
 154                 adev_virt_addr(adev), 0, apbt_freq);
 155         /* Firmware does EOI handling for us. */
 156         adev->timer->eoi = NULL;
 157
 158         if (intel_mid_timer_options == INTEL_MID_TIMER_LAPIC_APBT) {
 159                 global_clock_event = &adev->timer->ced;
 160                 printk(KERN_DEBUG "%s clockevent registered as global\n",
 161                        global_clock_event->name);
 162         }
 163
 164         dw_apb_clockevent_register(adev->timer);
 165
 166         sfi_free_mtmr(mtmr);
 167         return 0;
 168 }
 169
 170 #ifdef CONFIG_SMP
 171
 172 static void apbt_setup_irq(struct apbt_dev *adev)
 173 {
 174         irq_modify_status(adev->irq, 0, IRQ_MOVE_PCNTXT);
 175         irq_set_affinity(adev->irq, cpumask_of(adev->cpu));
 176 }
 177
 178 /* Should be called with per cpu */
 179 void apbt_setup_secondary_clock(void)
 180 {
 181         struct apbt_dev *adev;
 182         int cpu;
 183
 184         /* Don't register boot CPU clockevent */
 185         cpu = smp_processor_id();
 186         if (!cpu)
 187                 return;
 188
 189         adev = this_cpu_ptr(&cpu_apbt_dev);
 190         if (!adev->timer) {
 191                 adev->timer = dw_apb_clockevent_init(cpu, adev->name,
 192                         APBT_CLOCKEVENT_RATING, adev_virt_addr(adev),
 193                         adev->irq, apbt_freq);
 194                 adev->timer->eoi = NULL;
 195         } else {
 196                 dw_apb_clockevent_resume(adev->timer);
 197         }
 198
 199         printk(KERN_INFO "Registering CPU %d clockevent device %s, cpu %08x\n",
 200                cpu, adev->name, adev->cpu);
 201
 202         apbt_setup_irq(adev);
 203         dw_apb_clockevent_register(adev->timer);
 204
 205         return;
 206 }
 207
 208 /*
 209  * this notify handler process CPU hotplug events. in case of S0i3, nonboot
 210  * cpus are disabled/enabled frequently, for performance reasons, we keep the
 211  * per cpu timer irq registered so that we do need to do free_irq/request_irq.
 212  *
 213  * TODO: it might be more reliable to directly disable percpu clockevent device
 214  * without the notifier chain. currently, cpu 0 may get interrupts from other
 215  * cpu timers during the offline process due to the ordering of notification.
 216  * the extra interrupt is harmless.
 217  */
 218 static int apbt_cpuhp_notify(struct notifier_block *n,
 219                              unsigned long action, void *hcpu)
 220 {
 221         unsigned long cpu = (unsigned long)hcpu;
 222         struct apbt_dev *adev = &per_cpu(cpu_apbt_dev, cpu);
 223
 224         switch (action & ~CPU_TASKS_FROZEN) {
 225         case CPU_DEAD:
 226                 dw_apb_clockevent_pause(adev->timer);
 227                 if (system_state == SYSTEM_RUNNING) {
 228                         pr_debug("skipping APBT CPU %lu offline\n", cpu);
 229                 } else {
 230                         pr_debug("APBT clockevent for cpu %lu offline\n", cpu);
 231                         dw_apb_clockevent_stop(adev->timer);
 232                 }
 233                 break;
 234         default:
 235                 pr_debug("APBT notified %lu, no action\n", action);
 236         }
 237         return NOTIFY_OK;
 238 }
 239
 240 static __init int apbt_late_init(void)
 241 {
 242         if (intel_mid_timer_options == INTEL_MID_TIMER_LAPIC_APBT ||
 243                 !apb_timer_block_enabled)
 244                 return 0;
 245         /* This notifier should be called after workqueue is ready */
 246         hotcpu_notifier(apbt_cpuhp_notify, -20);
 247         return 0;
 248 }
 249 fs_initcall(apbt_late_init);
 250 #else
 251
 252 void apbt_setup_secondary_clock(void) {}
 253
 254 #endif /* CONFIG_SMP */
 255
 256 static int apbt_clocksource_register(void)
 257 {
 258         u64 start, now;
 259         cycle_t t1;
 260
 261         /* Start the counter, use timer 2 as source, timer 0/1 for event */
 262         dw_apb_clocksource_start(clocksource_apbt);
 263
 264         /* Verify whether apbt counter works */
 265         t1 = dw_apb_clocksource_read(clocksource_apbt);
 266         start = rdtsc();
 267
 268         /*
 269          * We don't know the TSC frequency yet, but waiting for
 270          * 200000 TSC cycles is safe:
 271          * 4 GHz == 50us
 272          * 1 GHz == 200us
 273          */
 274         do {
 275                 rep_nop();
 276                 now = rdtsc();
 277         } while ((now - start) < 200000UL);
 278
 279         /* APBT is the only always on clocksource, it has to work! */
 280         if (t1 == dw_apb_clocksource_read(clocksource_apbt))
 281                 panic("APBT counter not counting. APBT disabled\n");
 282
 283         dw_apb_clocksource_register(clocksource_apbt);
 284
 285         return 0;
 286 }
 287
 288 /*
 289  * Early setup the APBT timer, only use timer 0 for booting then switch to
 290  * per CPU timer if possible.
 291  * returns 1 if per cpu apbt is setup
 292  * returns 0 if no per cpu apbt is chosen
 293  * panic if set up failed, this is the only platform timer on Moorestown.
 294  */
 295 void __init apbt_time_init(void)
 296 {
 297 #ifdef CONFIG_SMP
 298         int i;
 299         struct sfi_timer_table_entry *p_mtmr;
 300         struct apbt_dev *adev;
 301 #endif
 302
 303         if (apb_timer_block_enabled)
 304                 return;
 305         apbt_set_mapping();
 306         if (!apbt_virt_address)
 307                 goto out_noapbt;
 308         /*
 309          * Read the frequency and check for a sane value, for ESL model
 310          * we extend the possible clock range to allow time scaling.
 311          */
 312
 313         if (apbt_freq < APBT_MIN_FREQ || apbt_freq > APBT_MAX_FREQ) {
 314                 pr_debug("APBT has invalid freq 0x%lx\n", apbt_freq);
 315                 goto out_noapbt;
 316         }
 317         if (apbt_clocksource_register()) {
 318                 pr_debug("APBT has failed to register clocksource\n");
 319                 goto out_noapbt;
 320         }
 321         if (!apbt_clockevent_register())
 322                 apb_timer_block_enabled = 1;
 323         else {
 324                 pr_debug("APBT has failed to register clockevent\n");
 325                 goto out_noapbt;
 326         }
 327 #ifdef CONFIG_SMP
 328         /* kernel cmdline disable apb timer, so we will use lapic timers */
 329         if (intel_mid_timer_options == INTEL_MID_TIMER_LAPIC_APBT) {
 330                 printk(KERN_INFO "apbt: disabled per cpu timer\n");
 331                 return;
 332         }
 333         pr_debug("%s: %d CPUs online\n", __func__, num_online_cpus());
 334         if (num_possible_cpus() <= sfi_mtimer_num)
 335                 apbt_num_timers_used = num_possible_cpus();
 336         else
 337                 apbt_num_timers_used = 1;
 338         pr_debug("%s: %d APB timers used\n", __func__, apbt_num_timers_used);
 339
 340         /* here we set up per CPU timer data structure */
 341         for (i = 0; i < apbt_num_timers_used; i++) {
 342                 adev = &per_cpu(cpu_apbt_dev, i);
 343                 adev->num = i;
 344                 adev->cpu = i;
 345                 p_mtmr = sfi_get_mtmr(i);
 346                 if (p_mtmr)
 347                         adev->irq = p_mtmr->irq;
 348                 else
 349                         printk(KERN_ERR "Failed to get timer for cpu %d\n", i);
 350                 snprintf(adev->name, sizeof(adev->name) - 1, "apbt%d", i);
 351         }
 352 #endif
 353
 354         return;
 355
 356 out_noapbt:
 357         apbt_clear_mapping();
 358         apb_timer_block_enabled = 0;
 359         panic("failed to enable APB timer\n");
 360 }
 361
 362 /* called before apb_timer_enable, use early map */
 363 unsigned long apbt_quick_calibrate(void)
 364 {
 365         int i, scale;
 366         u64 old, new;
 367         cycle_t t1, t2;
 368         unsigned long khz = 0;
 369         u32 loop, shift;
 370
 371         apbt_set_mapping();
 372         dw_apb_clocksource_start(clocksource_apbt);
 373
 374         /* check if the timer can count down, otherwise return */
 375         old = dw_apb_clocksource_read(clocksource_apbt);
 376         i = 10000;
 377         while (--i) {
 378                 if (old != dw_apb_clocksource_read(clocksource_apbt))
 379                         break;
 380         }
 381         if (!i)
 382                 goto failed;
 383
 384         /* count 16 ms */
 385         loop = (apbt_freq / 1000) << 4;
 386
 387         /* restart the timer to ensure it won't get to 0 in the calibration */
 388         dw_apb_clocksource_start(clocksource_apbt);
 389
 390         old = dw_apb_clocksource_read(clocksource_apbt);
 391         old += loop;
 392
 393         t1 = rdtsc();
 394
 395         do {
 396                 new = dw_apb_clocksource_read(clocksource_apbt);
 397         } while (new < old);
 398
 399         t2 = rdtsc();
 400
 401         shift = 5;
 402         if (unlikely(loop >> shift == 0)) {
 403                 printk(KERN_INFO
 404                        "APBT TSC calibration failed, not enough resolution\n");
 405                 return 0;
 406         }
 407         scale = (int)div_u64((t2 - t1), loop >> shift);
 408         khz = (scale * (apbt_freq / 1000)) >> shift;
 409         printk(KERN_INFO "TSC freq calculated by APB timer is %lu khz\n", khz);
 410         return khz;
 411 failed:
 412         return 0;
 413 }