drivers/clocksource/arm_global_timer.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * drivers/clocksource/arm_global_timer.c
   4  *
   5  * Copyright (C) 2013 STMicroelectronics (R&D) Limited.
   6  * Author: Stuart Menefy <stuart.menefy@st.com>
   7  * Author: Srinivas Kandagatla <srinivas.kandagatla@st.com>
   8  */
   9
  10 #include <linux/init.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/bitfield.h>
  13 #include <linux/clocksource.h>
  14 #include <linux/clockchips.h>
  15 #include <linux/cpu.h>
  16 #include <linux/clk.h>
  17 #include <linux/delay.h>
  18 #include <linux/err.h>
  19 #include <linux/io.h>
  20 #include <linux/of.h>
  21 #include <linux/of_irq.h>
  22 #include <linux/of_address.h>
  23 #include <linux/sched_clock.h>
  24
  25 #include <asm/cputype.h>
  26
  27 #define GT_COUNTER0     0x00
  28 #define GT_COUNTER1     0x04
  29
  30 #define GT_CONTROL      0x08
  31 #define GT_CONTROL_TIMER_ENABLE         BIT(0)  /* this bit is NOT banked */
  32 #define GT_CONTROL_COMP_ENABLE          BIT(1)  /* banked */
  33 #define GT_CONTROL_IRQ_ENABLE           BIT(2)  /* banked */
  34 #define GT_CONTROL_AUTO_INC             BIT(3)  /* banked */
  35 #define GT_CONTROL_PRESCALER_MASK       GENMASK(15, 8)
  36
  37 #define GT_INT_STATUS   0x0c
  38 #define GT_INT_STATUS_EVENT_FLAG        BIT(0)
  39
  40 #define GT_COMP0        0x10
  41 #define GT_COMP1        0x14
  42 #define GT_AUTO_INC     0x18
  43
  44 #define MAX_F_ERR 50
  45 /*
  46  * We are expecting to be clocked by the ARM peripheral clock.
  47  *
  48  * Note: it is assumed we are using a prescaler value of zero, so this is
  49  * the units for all operations.
  50  */
  51 static void __iomem *gt_base;
  52 static struct notifier_block gt_clk_rate_change_nb;
  53 static u32 gt_psv_new, gt_psv_bck;
  54 static unsigned long gt_target_rate;
  55 static int gt_ppi;
  56 static struct clock_event_device __percpu *gt_evt;
  57
  58 /*
  59  * To get the value from the Global Timer Counter register proceed as follows:
  60  * 1. Read the upper 32-bit timer counter register
  61  * 2. Read the lower 32-bit timer counter register
  62  * 3. Read the upper 32-bit timer counter register again. If the value is
  63  *  different to the 32-bit upper value read previously, go back to step 2.
  64  *  Otherwise the 64-bit timer counter value is correct.
  65  */
  66 static u64 notrace _gt_counter_read(void)
  67 {
  68         u64 counter;
  69         u32 lower;
  70         u32 upper, old_upper;
  71
  72         upper = readl_relaxed(gt_base + GT_COUNTER1);
  73         do {
  74                 old_upper = upper;
  75                 lower = readl_relaxed(gt_base + GT_COUNTER0);
  76                 upper = readl_relaxed(gt_base + GT_COUNTER1);
  77         } while (upper != old_upper);
  78
  79         counter = upper;
  80         counter <<= 32;
  81         counter |= lower;
  82         return counter;
  83 }
  84
  85 static u64 gt_counter_read(void)
  86 {
  87         return _gt_counter_read();
  88 }
  89
  90 /*
  91  * To ensure that updates to comparator value register do not set the
  92  * Interrupt Status Register proceed as follows:
  93  * 1. Clear the Comp Enable bit in the Timer Control Register.
  94  * 2. Write the lower 32-bit Comparator Value Register.
  95  * 3. Write the upper 32-bit Comparator Value Register.
  96  * 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit.
  97  */
  98 static void gt_compare_set(unsigned long delta, int periodic)
  99 {
 100         u64 counter = gt_counter_read();
 101         unsigned long ctrl;
 102
 103         counter += delta;
 104         ctrl = readl(gt_base + GT_CONTROL);
 105         ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE |
 106                   GT_CONTROL_AUTO_INC);
 107         ctrl |= GT_CONTROL_TIMER_ENABLE;
 108         writel_relaxed(ctrl, gt_base + GT_CONTROL);
 109         writel_relaxed(lower_32_bits(counter), gt_base + GT_COMP0);
 110         writel_relaxed(upper_32_bits(counter), gt_base + GT_COMP1);
 111
 112         if (periodic) {
 113                 writel_relaxed(delta, gt_base + GT_AUTO_INC);
 114                 ctrl |= GT_CONTROL_AUTO_INC;
 115         }
 116
 117         ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
 118         writel_relaxed(ctrl, gt_base + GT_CONTROL);
 119 }
 120
 121 static int gt_clockevent_shutdown(struct clock_event_device *evt)
 122 {
 123         unsigned long ctrl;
 124
 125         ctrl = readl(gt_base + GT_CONTROL);
 126         ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE |
 127                   GT_CONTROL_AUTO_INC);
 128         writel(ctrl, gt_base + GT_CONTROL);
 129         return 0;
 130 }
 131
 132 static int gt_clockevent_set_periodic(struct clock_event_device *evt)
 133 {
 134         gt_compare_set(DIV_ROUND_CLOSEST(gt_target_rate, HZ), 1);
 135         return 0;
 136 }
 137
 138 static int gt_clockevent_set_next_event(unsigned long evt,
 139                                         struct clock_event_device *unused)
 140 {
 141         gt_compare_set(evt, 0);
 142         return 0;
 143 }
 144
 145 static irqreturn_t gt_clockevent_interrupt(int irq, void *dev_id)
 146 {
 147         struct clock_event_device *evt = dev_id;
 148
 149         if (!(readl_relaxed(gt_base + GT_INT_STATUS) &
 150                                 GT_INT_STATUS_EVENT_FLAG))
 151                 return IRQ_NONE;
 152
 153         /**
 154          * ERRATA 740657( Global Timer can send 2 interrupts for
 155          * the same event in single-shot mode)
 156          * Workaround:
 157          *      Either disable single-shot mode.
 158          *      Or
 159          *      Modify the Interrupt Handler to avoid the
 160          *      offending sequence. This is achieved by clearing
 161          *      the Global Timer flag _after_ having incremented
 162          *      the Comparator register value to a higher value.
 163          */
 164         if (clockevent_state_oneshot(evt))
 165                 gt_compare_set(ULONG_MAX, 0);
 166
 167         writel_relaxed(GT_INT_STATUS_EVENT_FLAG, gt_base + GT_INT_STATUS);
 168         evt->event_handler(evt);
 169
 170         return IRQ_HANDLED;
 171 }
 172
 173 static int gt_starting_cpu(unsigned int cpu)
 174 {
 175         struct clock_event_device *clk = this_cpu_ptr(gt_evt);
 176
 177         clk->name = "arm_global_timer";
 178         clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
 179                 CLOCK_EVT_FEAT_PERCPU;
 180         clk->set_state_shutdown = gt_clockevent_shutdown;
 181         clk->set_state_periodic = gt_clockevent_set_periodic;
 182         clk->set_state_oneshot = gt_clockevent_shutdown;
 183         clk->set_state_oneshot_stopped = gt_clockevent_shutdown;
 184         clk->set_next_event = gt_clockevent_set_next_event;
 185         clk->cpumask = cpumask_of(cpu);
 186         clk->rating = 300;
 187         clk->irq = gt_ppi;
 188         clockevents_config_and_register(clk, gt_target_rate,
 189                                         1, 0xffffffff);
 190         enable_percpu_irq(clk->irq, IRQ_TYPE_NONE);
 191         return 0;
 192 }
 193
 194 static int gt_dying_cpu(unsigned int cpu)
 195 {
 196         struct clock_event_device *clk = this_cpu_ptr(gt_evt);
 197
 198         disable_percpu_irq(clk->irq);
 199         return 0;
 200 }
 201
 202 static u64 gt_clocksource_read(struct clocksource *cs)
 203 {
 204         return gt_counter_read();
 205 }
 206
 207 static void gt_resume(struct clocksource *cs)
 208 {
 209         unsigned long ctrl;
 210
 211         ctrl = readl(gt_base + GT_CONTROL);
 212         if (!(ctrl & GT_CONTROL_TIMER_ENABLE))
 213                 /* re-enable timer on resume */
 214                 writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
 215 }
 216
 217 static struct clocksource gt_clocksource = {
 218         .name   = "arm_global_timer",
 219         .rating = 300,
 220         .read   = gt_clocksource_read,
 221         .mask   = CLOCKSOURCE_MASK(64),
 222         .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 223         .resume = gt_resume,
 224 };
 225
 226 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
 227 static u64 notrace gt_sched_clock_read(void)
 228 {
 229         return _gt_counter_read();
 230 }
 231 #endif
 232
 233 static unsigned long gt_read_long(void)
 234 {
 235         return readl_relaxed(gt_base + GT_COUNTER0);
 236 }
 237
 238 static struct delay_timer gt_delay_timer = {
 239         .read_current_timer = gt_read_long,
 240 };
 241
 242 static void gt_write_presc(u32 psv)
 243 {
 244         u32 reg;
 245
 246         reg = readl(gt_base + GT_CONTROL);
 247         reg &= ~GT_CONTROL_PRESCALER_MASK;
 248         reg |= FIELD_PREP(GT_CONTROL_PRESCALER_MASK, psv);
 249         writel(reg, gt_base + GT_CONTROL);
 250 }
 251
 252 static u32 gt_read_presc(void)
 253 {
 254         u32 reg;
 255
 256         reg = readl(gt_base + GT_CONTROL);
 257         return FIELD_GET(GT_CONTROL_PRESCALER_MASK, reg);
 258 }
 259
 260 static void __init gt_delay_timer_init(void)
 261 {
 262         gt_delay_timer.freq = gt_target_rate;
 263         register_current_timer_delay(&gt_delay_timer);
 264 }
 265
 266 static int __init gt_clocksource_init(void)
 267 {
 268         writel(0, gt_base + GT_CONTROL);
 269         writel(0, gt_base + GT_COUNTER0);
 270         writel(0, gt_base + GT_COUNTER1);
 271         /* set prescaler and enable timer on all the cores */
 272         writel(FIELD_PREP(GT_CONTROL_PRESCALER_MASK,
 273                           CONFIG_ARM_GT_INITIAL_PRESCALER_VAL - 1) |
 274                GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
 275
 276 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
 277         sched_clock_register(gt_sched_clock_read, 64, gt_target_rate);
 278 #endif
 279         return clocksource_register_hz(&gt_clocksource, gt_target_rate);
 280 }
 281
 282 static int gt_clk_rate_change_cb(struct notifier_block *nb,
 283                                  unsigned long event, void *data)
 284 {
 285         struct clk_notifier_data *ndata = data;
 286
 287         switch (event) {
 288         case PRE_RATE_CHANGE:
 289         {
 290                 unsigned long psv;
 291
 292                 psv = DIV_ROUND_CLOSEST(ndata->new_rate, gt_target_rate);
 293                 if (!psv ||
 294                     abs(gt_target_rate - (ndata->new_rate / psv)) > MAX_F_ERR)
 295                         return NOTIFY_BAD;
 296
 297                 psv--;
 298
 299                 /* prescaler within legal range? */
 300                 if (!FIELD_FIT(GT_CONTROL_PRESCALER_MASK, psv))
 301                         return NOTIFY_BAD;
 302
 303                 /*
 304                  * store timer clock ctrl register so we can restore it in case
 305                  * of an abort.
 306                  */
 307                 gt_psv_bck = gt_read_presc();
 308                 gt_psv_new = psv;
 309                 /* scale down: adjust divider in post-change notification */
 310                 if (ndata->new_rate < ndata->old_rate)
 311                         return NOTIFY_DONE;
 312
 313                 /* scale up: adjust divider now - before frequency change */
 314                 gt_write_presc(psv);
 315                 break;
 316         }
 317         case POST_RATE_CHANGE:
 318                 /* scale up: pre-change notification did the adjustment */
 319                 if (ndata->new_rate > ndata->old_rate)
 320                         return NOTIFY_OK;
 321
 322                 /* scale down: adjust divider now - after frequency change */
 323                 gt_write_presc(gt_psv_new);
 324                 break;
 325
 326         case ABORT_RATE_CHANGE:
 327                 /* we have to undo the adjustment in case we scale up */
 328                 if (ndata->new_rate < ndata->old_rate)
 329                         return NOTIFY_OK;
 330
 331                 /* restore original register value */
 332                 gt_write_presc(gt_psv_bck);
 333                 break;
 334         default:
 335                 return NOTIFY_DONE;
 336         }
 337
 338         return NOTIFY_DONE;
 339 }
 340
 341 static int __init global_timer_of_register(struct device_node *np)
 342 {
 343         struct clk *gt_clk;
 344         static unsigned long gt_clk_rate;
 345         int err;
 346
 347         /*
 348          * In A9 r2p0 the comparators for each processor with the global timer
 349          * fire when the timer value is greater than or equal to. In previous
 350          * revisions the comparators fired when the timer value was equal to.
 351          */
 352         if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9
 353             && (read_cpuid_id() & 0xf0000f) < 0x200000) {
 354                 pr_warn("global-timer: non support for this cpu version.\n");
 355                 return -ENOSYS;
 356         }
 357
 358         gt_ppi = irq_of_parse_and_map(np, 0);
 359         if (!gt_ppi) {
 360                 pr_warn("global-timer: unable to parse irq\n");
 361                 return -EINVAL;
 362         }
 363
 364         gt_base = of_iomap(np, 0);
 365         if (!gt_base) {
 366                 pr_warn("global-timer: invalid base address\n");
 367                 return -ENXIO;
 368         }
 369
 370         gt_clk = of_clk_get(np, 0);
 371         if (!IS_ERR(gt_clk)) {
 372                 err = clk_prepare_enable(gt_clk);
 373                 if (err)
 374                         goto out_unmap;
 375         } else {
 376                 pr_warn("global-timer: clk not found\n");
 377                 err = -EINVAL;
 378                 goto out_unmap;
 379         }
 380
 381         gt_clk_rate = clk_get_rate(gt_clk);
 382         gt_target_rate = gt_clk_rate / CONFIG_ARM_GT_INITIAL_PRESCALER_VAL;
 383         gt_clk_rate_change_nb.notifier_call =
 384                 gt_clk_rate_change_cb;
 385         err = clk_notifier_register(gt_clk, &gt_clk_rate_change_nb);
 386         if (err) {
 387                 pr_warn("Unable to register clock notifier\n");
 388                 goto out_clk;
 389         }
 390
 391         gt_evt = alloc_percpu(struct clock_event_device);
 392         if (!gt_evt) {
 393                 pr_warn("global-timer: can't allocate memory\n");
 394                 err = -ENOMEM;
 395                 goto out_clk_nb;
 396         }
 397
 398         err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt,
 399                                  "gt", gt_evt);
 400         if (err) {
 401                 pr_warn("global-timer: can't register interrupt %d (%d)\n",
 402                         gt_ppi, err);
 403                 goto out_free;
 404         }
 405
 406         /* Register and immediately configure the timer on the boot CPU */
 407         err = gt_clocksource_init();
 408         if (err)
 409                 goto out_irq;
 410
 411         err = cpuhp_setup_state(CPUHP_AP_ARM_GLOBAL_TIMER_STARTING,
 412                                 "clockevents/arm/global_timer:starting",
 413                                 gt_starting_cpu, gt_dying_cpu);
 414         if (err)
 415                 goto out_irq;
 416
 417         gt_delay_timer_init();
 418
 419         return 0;
 420
 421 out_irq:
 422         free_percpu_irq(gt_ppi, gt_evt);
 423 out_free:
 424         free_percpu(gt_evt);
 425 out_clk_nb:
 426         clk_notifier_unregister(gt_clk, &gt_clk_rate_change_nb);
 427 out_clk:
 428         clk_disable_unprepare(gt_clk);
 429 out_unmap:
 430         iounmap(gt_base);
 431         WARN(err, "ARM Global timer register failed (%d)\n", err);
 432
 433         return err;
 434 }
 435
 436 /* Only tested on r2p2 and r3p0  */
 437 TIMER_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
 438                         global_timer_of_register);