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 /*
 139  * APBT timer interrupt enable / disable
 140  */
 141 static inline int is_apbt_capable(void)
 142 {
 143         return apbt_virt_address ? 1 : 0;
 144 }
 145
 146 static int __init apbt_clockevent_register(void)
 147 {
 148         struct sfi_timer_table_entry *mtmr;
 149         struct apbt_dev *adev = this_cpu_ptr(&cpu_apbt_dev);
 150
 151         mtmr = sfi_get_mtmr(APBT_CLOCKEVENT0_NUM);
 152         if (mtmr == NULL) {
 153                 printk(KERN_ERR "Failed to get MTMR %d from SFI\n",
 154                        APBT_CLOCKEVENT0_NUM);
 155                 return -ENODEV;
 156         }
 157
 158         adev->num = smp_processor_id();
 159         adev->timer = dw_apb_clockevent_init(smp_processor_id(), "apbt0",
 160                 intel_mid_timer_options == INTEL_MID_TIMER_LAPIC_APBT ?
 161                 APBT_CLOCKEVENT_RATING - 100 : APBT_CLOCKEVENT_RATING,
 162                 adev_virt_addr(adev), 0, apbt_freq);
 163         /* Firmware does EOI handling for us. */
 164         adev->timer->eoi = NULL;
 165
 166         if (intel_mid_timer_options == INTEL_MID_TIMER_LAPIC_APBT) {
 167                 global_clock_event = &adev->timer->ced;
 168                 printk(KERN_DEBUG "%s clockevent registered as global\n",
 169                        global_clock_event->name);
 170         }
 171
 172         dw_apb_clockevent_register(adev->timer);
 173
 174         sfi_free_mtmr(mtmr);
 175         return 0;
 176 }
 177
 178 #ifdef CONFIG_SMP
 179
 180 static void apbt_setup_irq(struct apbt_dev *adev)
 181 {
 182         /* timer0 irq has been setup early */
 183         if (adev->irq == 0)
 184                 return;
 185
 186         irq_modify_status(adev->irq, 0, IRQ_MOVE_PCNTXT);
 187         irq_set_affinity(adev->irq, cpumask_of(adev->cpu));
 188 }
 189
 190 /* Should be called with per cpu */
 191 void apbt_setup_secondary_clock(void)
 192 {
 193         struct apbt_dev *adev;
 194         int cpu;
 195
 196         /* Don't register boot CPU clockevent */
 197         cpu = smp_processor_id();
 198         if (!cpu)
 199                 return;
 200
 201         adev = this_cpu_ptr(&cpu_apbt_dev);
 202         if (!adev->timer) {
 203                 adev->timer = dw_apb_clockevent_init(cpu, adev->name,
 204                         APBT_CLOCKEVENT_RATING, adev_virt_addr(adev),
 205                         adev->irq, apbt_freq);
 206                 adev->timer->eoi = NULL;
 207         } else {
 208                 dw_apb_clockevent_resume(adev->timer);
 209         }
 210
 211         printk(KERN_INFO "Registering CPU %d clockevent device %s, cpu %08x\n",
 212                cpu, adev->name, adev->cpu);
 213
 214         apbt_setup_irq(adev);
 215         dw_apb_clockevent_register(adev->timer);
 216
 217         return;
 218 }
 219
 220 /*
 221  * this notify handler process CPU hotplug events. in case of S0i3, nonboot
 222  * cpus are disabled/enabled frequently, for performance reasons, we keep the
 223  * per cpu timer irq registered so that we do need to do free_irq/request_irq.
 224  *
 225  * TODO: it might be more reliable to directly disable percpu clockevent device
 226  * without the notifier chain. currently, cpu 0 may get interrupts from other
 227  * cpu timers during the offline process due to the ordering of notification.
 228  * the extra interrupt is harmless.
 229  */
 230 static int apbt_cpuhp_notify(struct notifier_block *n,
 231                              unsigned long action, void *hcpu)
 232 {
 233         unsigned long cpu = (unsigned long)hcpu;
 234         struct apbt_dev *adev = &per_cpu(cpu_apbt_dev, cpu);
 235
 236         switch (action & 0xf) {
 237         case CPU_DEAD:
 238                 dw_apb_clockevent_pause(adev->timer);
 239                 if (system_state == SYSTEM_RUNNING) {
 240                         pr_debug("skipping APBT CPU %lu offline\n", cpu);
 241                 } else {
 242                         pr_debug("APBT clockevent for cpu %lu offline\n", cpu);
 243                         dw_apb_clockevent_stop(adev->timer);
 244                 }
 245                 break;
 246         default:
 247                 pr_debug("APBT notified %lu, no action\n", action);
 248         }
 249         return NOTIFY_OK;
 250 }
 251
 252 static __init int apbt_late_init(void)
 253 {
 254         if (intel_mid_timer_options == INTEL_MID_TIMER_LAPIC_APBT ||
 255                 !apb_timer_block_enabled)
 256                 return 0;
 257         /* This notifier should be called after workqueue is ready */
 258         hotcpu_notifier(apbt_cpuhp_notify, -20);
 259         return 0;
 260 }
 261 fs_initcall(apbt_late_init);
 262 #else
 263
 264 void apbt_setup_secondary_clock(void) {}
 265
 266 #endif /* CONFIG_SMP */
 267
 268 static int apbt_clocksource_register(void)
 269 {
 270         u64 start, now;
 271         cycle_t t1;
 272
 273         /* Start the counter, use timer 2 as source, timer 0/1 for event */
 274         dw_apb_clocksource_start(clocksource_apbt);
 275
 276         /* Verify whether apbt counter works */
 277         t1 = dw_apb_clocksource_read(clocksource_apbt);
 278         rdtscll(start);
 279
 280         /*
 281          * We don't know the TSC frequency yet, but waiting for
 282          * 200000 TSC cycles is safe:
 283          * 4 GHz == 50us
 284          * 1 GHz == 200us
 285          */
 286         do {
 287                 rep_nop();
 288                 rdtscll(now);
 289         } while ((now - start) < 200000UL);
 290
 291         /* APBT is the only always on clocksource, it has to work! */
 292         if (t1 == dw_apb_clocksource_read(clocksource_apbt))
 293                 panic("APBT counter not counting. APBT disabled\n");
 294
 295         dw_apb_clocksource_register(clocksource_apbt);
 296
 297         return 0;
 298 }
 299
 300 /*
 301  * Early setup the APBT timer, only use timer 0 for booting then switch to
 302  * per CPU timer if possible.
 303  * returns 1 if per cpu apbt is setup
 304  * returns 0 if no per cpu apbt is chosen
 305  * panic if set up failed, this is the only platform timer on Moorestown.
 306  */
 307 void __init apbt_time_init(void)
 308 {
 309 #ifdef CONFIG_SMP
 310         int i;
 311         struct sfi_timer_table_entry *p_mtmr;
 312         struct apbt_dev *adev;
 313 #endif
 314
 315         if (apb_timer_block_enabled)
 316                 return;
 317         apbt_set_mapping();
 318         if (!apbt_virt_address)
 319                 goto out_noapbt;
 320         /*
 321          * Read the frequency and check for a sane value, for ESL model
 322          * we extend the possible clock range to allow time scaling.
 323          */
 324
 325         if (apbt_freq < APBT_MIN_FREQ || apbt_freq > APBT_MAX_FREQ) {
 326                 pr_debug("APBT has invalid freq 0x%lx\n", apbt_freq);
 327                 goto out_noapbt;
 328         }
 329         if (apbt_clocksource_register()) {
 330                 pr_debug("APBT has failed to register clocksource\n");
 331                 goto out_noapbt;
 332         }
 333         if (!apbt_clockevent_register())
 334                 apb_timer_block_enabled = 1;
 335         else {
 336                 pr_debug("APBT has failed to register clockevent\n");
 337                 goto out_noapbt;
 338         }
 339 #ifdef CONFIG_SMP
 340         /* kernel cmdline disable apb timer, so we will use lapic timers */
 341         if (intel_mid_timer_options == INTEL_MID_TIMER_LAPIC_APBT) {
 342                 printk(KERN_INFO "apbt: disabled per cpu timer\n");
 343                 return;
 344         }
 345         pr_debug("%s: %d CPUs online\n", __func__, num_online_cpus());
 346         if (num_possible_cpus() <= sfi_mtimer_num)
 347                 apbt_num_timers_used = num_possible_cpus();
 348         else
 349                 apbt_num_timers_used = 1;
 350         pr_debug("%s: %d APB timers used\n", __func__, apbt_num_timers_used);
 351
 352         /* here we set up per CPU timer data structure */
 353         for (i = 0; i < apbt_num_timers_used; i++) {
 354                 adev = &per_cpu(cpu_apbt_dev, i);
 355                 adev->num = i;
 356                 adev->cpu = i;
 357                 p_mtmr = sfi_get_mtmr(i);
 358                 if (p_mtmr)
 359                         adev->irq = p_mtmr->irq;
 360                 else
 361                         printk(KERN_ERR "Failed to get timer for cpu %d\n", i);
 362                 snprintf(adev->name, sizeof(adev->name) - 1, "apbt%d", i);
 363         }
 364 #endif
 365
 366         return;
 367
 368 out_noapbt:
 369         apbt_clear_mapping();
 370         apb_timer_block_enabled = 0;
 371         panic("failed to enable APB timer\n");
 372 }
 373
 374 /* called before apb_timer_enable, use early map */
 375 unsigned long apbt_quick_calibrate(void)
 376 {
 377         int i, scale;
 378         u64 old, new;
 379         cycle_t t1, t2;
 380         unsigned long khz = 0;
 381         u32 loop, shift;
 382
 383         apbt_set_mapping();
 384         dw_apb_clocksource_start(clocksource_apbt);
 385
 386         /* check if the timer can count down, otherwise return */
 387         old = dw_apb_clocksource_read(clocksource_apbt);
 388         i = 10000;
 389         while (--i) {
 390                 if (old != dw_apb_clocksource_read(clocksource_apbt))
 391                         break;
 392         }
 393         if (!i)
 394                 goto failed;
 395
 396         /* count 16 ms */
 397         loop = (apbt_freq / 1000) << 4;
 398
 399         /* restart the timer to ensure it won't get to 0 in the calibration */
 400         dw_apb_clocksource_start(clocksource_apbt);
 401
 402         old = dw_apb_clocksource_read(clocksource_apbt);
 403         old += loop;
 404
 405         t1 = __native_read_tsc();
 406
 407         do {
 408                 new = dw_apb_clocksource_read(clocksource_apbt);
 409         } while (new < old);
 410
 411         t2 = __native_read_tsc();
 412
 413         shift = 5;
 414         if (unlikely(loop >> shift == 0)) {
 415                 printk(KERN_INFO
 416                        "APBT TSC calibration failed, not enough resolution\n");
 417                 return 0;
 418         }
 419         scale = (int)div_u64((t2 - t1), loop >> shift);
 420         khz = (scale * (apbt_freq / 1000)) >> shift;
 421         printk(KERN_INFO "TSC freq calculated by APB timer is %lu khz\n", khz);
 422         return khz;
 423 failed:
 424         return 0;
 425 }