drivers/clocksource/arm_global_timer.c

   1 /*
   2  * drivers/clocksource/arm_global_timer.c
   3  *
   4  * Copyright (C) 2013 STMicroelectronics (R&D) Limited.
   5  * Author: Stuart Menefy <stuart.menefy@st.com>
   6  * Author: Srinivas Kandagatla <srinivas.kandagatla@st.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/init.h>
  14 #include <linux/interrupt.h>
  15 #include <linux/clocksource.h>
  16 #include <linux/clockchips.h>
  17 #include <linux/cpu.h>
  18 #include <linux/clk.h>
  19 #include <linux/delay.h>
  20 #include <linux/err.h>
  21 #include <linux/io.h>
  22 #include <linux/of.h>
  23 #include <linux/of_irq.h>
  24 #include <linux/of_address.h>
  25 #include <linux/sched_clock.h>
  26
  27 #include <asm/cputype.h>
  28
  29 #define GT_COUNTER0     0x00
  30 #define GT_COUNTER1     0x04
  31
  32 #define GT_CONTROL      0x08
  33 #define GT_CONTROL_TIMER_ENABLE         BIT(0)  /* this bit is NOT banked */
  34 #define GT_CONTROL_COMP_ENABLE          BIT(1)  /* banked */
  35 #define GT_CONTROL_IRQ_ENABLE           BIT(2)  /* banked */
  36 #define GT_CONTROL_AUTO_INC             BIT(3)  /* banked */
  37
  38 #define GT_INT_STATUS   0x0c
  39 #define GT_INT_STATUS_EVENT_FLAG        BIT(0)
  40
  41 #define GT_COMP0        0x10
  42 #define GT_COMP1        0x14
  43 #define GT_AUTO_INC     0x18
  44
  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 unsigned long gt_clk_rate;
  53 static int gt_ppi;
  54 static struct clock_event_device __percpu *gt_evt;
  55
  56 /*
  57  * To get the value from the Global Timer Counter register proceed as follows:
  58  * 1. Read the upper 32-bit timer counter register
  59  * 2. Read the lower 32-bit timer counter register
  60  * 3. Read the upper 32-bit timer counter register again. If the value is
  61  *  different to the 32-bit upper value read previously, go back to step 2.
  62  *  Otherwise the 64-bit timer counter value is correct.
  63  */
  64 static u64 notrace _gt_counter_read(void)
  65 {
  66         u64 counter;
  67         u32 lower;
  68         u32 upper, old_upper;
  69
  70         upper = readl_relaxed(gt_base + GT_COUNTER1);
  71         do {
  72                 old_upper = upper;
  73                 lower = readl_relaxed(gt_base + GT_COUNTER0);
  74                 upper = readl_relaxed(gt_base + GT_COUNTER1);
  75         } while (upper != old_upper);
  76
  77         counter = upper;
  78         counter <<= 32;
  79         counter |= lower;
  80         return counter;
  81 }
  82
  83 static u64 gt_counter_read(void)
  84 {
  85         return _gt_counter_read();
  86 }
  87
  88 /**
  89  * To ensure that updates to comparator value register do not set the
  90  * Interrupt Status Register proceed as follows:
  91  * 1. Clear the Comp Enable bit in the Timer Control Register.
  92  * 2. Write the lower 32-bit Comparator Value Register.
  93  * 3. Write the upper 32-bit Comparator Value Register.
  94  * 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit.
  95  */
  96 static void gt_compare_set(unsigned long delta, int periodic)
  97 {
  98         u64 counter = gt_counter_read();
  99         unsigned long ctrl;
 100
 101         counter += delta;
 102         ctrl = GT_CONTROL_TIMER_ENABLE;
 103         writel_relaxed(ctrl, gt_base + GT_CONTROL);
 104         writel_relaxed(lower_32_bits(counter), gt_base + GT_COMP0);
 105         writel_relaxed(upper_32_bits(counter), gt_base + GT_COMP1);
 106
 107         if (periodic) {
 108                 writel_relaxed(delta, gt_base + GT_AUTO_INC);
 109                 ctrl |= GT_CONTROL_AUTO_INC;
 110         }
 111
 112         ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
 113         writel_relaxed(ctrl, gt_base + GT_CONTROL);
 114 }
 115
 116 static int gt_clockevent_shutdown(struct clock_event_device *evt)
 117 {
 118         unsigned long ctrl;
 119
 120         ctrl = readl(gt_base + GT_CONTROL);
 121         ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE |
 122                   GT_CONTROL_AUTO_INC);
 123         writel(ctrl, gt_base + GT_CONTROL);
 124         return 0;
 125 }
 126
 127 static int gt_clockevent_set_periodic(struct clock_event_device *evt)
 128 {
 129         gt_compare_set(DIV_ROUND_CLOSEST(gt_clk_rate, HZ), 1);
 130         return 0;
 131 }
 132
 133 static int gt_clockevent_set_next_event(unsigned long evt,
 134                                         struct clock_event_device *unused)
 135 {
 136         gt_compare_set(evt, 0);
 137         return 0;
 138 }
 139
 140 static irqreturn_t gt_clockevent_interrupt(int irq, void *dev_id)
 141 {
 142         struct clock_event_device *evt = dev_id;
 143
 144         if (!(readl_relaxed(gt_base + GT_INT_STATUS) &
 145                                 GT_INT_STATUS_EVENT_FLAG))
 146                 return IRQ_NONE;
 147
 148         /**
 149          * ERRATA 740657( Global Timer can send 2 interrupts for
 150          * the same event in single-shot mode)
 151          * Workaround:
 152          *      Either disable single-shot mode.
 153          *      Or
 154          *      Modify the Interrupt Handler to avoid the
 155          *      offending sequence. This is achieved by clearing
 156          *      the Global Timer flag _after_ having incremented
 157          *      the Comparator register value to a higher value.
 158          */
 159         if (clockevent_state_oneshot(evt))
 160                 gt_compare_set(ULONG_MAX, 0);
 161
 162         writel_relaxed(GT_INT_STATUS_EVENT_FLAG, gt_base + GT_INT_STATUS);
 163         evt->event_handler(evt);
 164
 165         return IRQ_HANDLED;
 166 }
 167
 168 static int gt_starting_cpu(unsigned int cpu)
 169 {
 170         struct clock_event_device *clk = this_cpu_ptr(gt_evt);
 171
 172         clk->name = "arm_global_timer";
 173         clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
 174                 CLOCK_EVT_FEAT_PERCPU;
 175         clk->set_state_shutdown = gt_clockevent_shutdown;
 176         clk->set_state_periodic = gt_clockevent_set_periodic;
 177         clk->set_state_oneshot = gt_clockevent_shutdown;
 178         clk->set_state_oneshot_stopped = gt_clockevent_shutdown;
 179         clk->set_next_event = gt_clockevent_set_next_event;
 180         clk->cpumask = cpumask_of(cpu);
 181         clk->rating = 300;
 182         clk->irq = gt_ppi;
 183         clockevents_config_and_register(clk, gt_clk_rate,
 184                                         1, 0xffffffff);
 185         enable_percpu_irq(clk->irq, IRQ_TYPE_NONE);
 186         return 0;
 187 }
 188
 189 static int gt_dying_cpu(unsigned int cpu)
 190 {
 191         struct clock_event_device *clk = this_cpu_ptr(gt_evt);
 192
 193         gt_clockevent_shutdown(clk);
 194         disable_percpu_irq(clk->irq);
 195         return 0;
 196 }
 197
 198 static u64 gt_clocksource_read(struct clocksource *cs)
 199 {
 200         return gt_counter_read();
 201 }
 202
 203 static void gt_resume(struct clocksource *cs)
 204 {
 205         unsigned long ctrl;
 206
 207         ctrl = readl(gt_base + GT_CONTROL);
 208         if (!(ctrl & GT_CONTROL_TIMER_ENABLE))
 209                 /* re-enable timer on resume */
 210                 writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
 211 }
 212
 213 static struct clocksource gt_clocksource = {
 214         .name   = "arm_global_timer",
 215         .rating = 300,
 216         .read   = gt_clocksource_read,
 217         .mask   = CLOCKSOURCE_MASK(64),
 218         .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 219         .resume = gt_resume,
 220 };
 221
 222 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
 223 static u64 notrace gt_sched_clock_read(void)
 224 {
 225         return _gt_counter_read();
 226 }
 227 #endif
 228
 229 static unsigned long gt_read_long(void)
 230 {
 231         return readl_relaxed(gt_base + GT_COUNTER0);
 232 }
 233
 234 static struct delay_timer gt_delay_timer = {
 235         .read_current_timer = gt_read_long,
 236 };
 237
 238 static void __init gt_delay_timer_init(void)
 239 {
 240         gt_delay_timer.freq = gt_clk_rate;
 241         register_current_timer_delay(&gt_delay_timer);
 242 }
 243
 244 static int __init gt_clocksource_init(void)
 245 {
 246         writel(0, gt_base + GT_CONTROL);
 247         writel(0, gt_base + GT_COUNTER0);
 248         writel(0, gt_base + GT_COUNTER1);
 249         /* enables timer on all the cores */
 250         writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
 251
 252 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
 253         sched_clock_register(gt_sched_clock_read, 64, gt_clk_rate);
 254 #endif
 255         return clocksource_register_hz(&gt_clocksource, gt_clk_rate);
 256 }
 257
 258 static int __init global_timer_of_register(struct device_node *np)
 259 {
 260         struct clk *gt_clk;
 261         int err = 0;
 262
 263         /*
 264          * In A9 r2p0 the comparators for each processor with the global timer
 265          * fire when the timer value is greater than or equal to. In previous
 266          * revisions the comparators fired when the timer value was equal to.
 267          */
 268         if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9
 269             && (read_cpuid_id() & 0xf0000f) < 0x200000) {
 270                 pr_warn("global-timer: non support for this cpu version.\n");
 271                 return -ENOSYS;
 272         }
 273
 274         gt_ppi = irq_of_parse_and_map(np, 0);
 275         if (!gt_ppi) {
 276                 pr_warn("global-timer: unable to parse irq\n");
 277                 return -EINVAL;
 278         }
 279
 280         gt_base = of_iomap(np, 0);
 281         if (!gt_base) {
 282                 pr_warn("global-timer: invalid base address\n");
 283                 return -ENXIO;
 284         }
 285
 286         gt_clk = of_clk_get(np, 0);
 287         if (!IS_ERR(gt_clk)) {
 288                 err = clk_prepare_enable(gt_clk);
 289                 if (err)
 290                         goto out_unmap;
 291         } else {
 292                 pr_warn("global-timer: clk not found\n");
 293                 err = -EINVAL;
 294                 goto out_unmap;
 295         }
 296
 297         gt_clk_rate = clk_get_rate(gt_clk);
 298         gt_evt = alloc_percpu(struct clock_event_device);
 299         if (!gt_evt) {
 300                 pr_warn("global-timer: can't allocate memory\n");
 301                 err = -ENOMEM;
 302                 goto out_clk;
 303         }
 304
 305         err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt,
 306                                  "gt", gt_evt);
 307         if (err) {
 308                 pr_warn("global-timer: can't register interrupt %d (%d)\n",
 309                         gt_ppi, err);
 310                 goto out_free;
 311         }
 312
 313         /* Register and immediately configure the timer on the boot CPU */
 314         err = gt_clocksource_init();
 315         if (err)
 316                 goto out_irq;
 317
 318         err = cpuhp_setup_state(CPUHP_AP_ARM_GLOBAL_TIMER_STARTING,
 319                                 "clockevents/arm/global_timer:starting",
 320                                 gt_starting_cpu, gt_dying_cpu);
 321         if (err)
 322                 goto out_irq;
 323
 324         gt_delay_timer_init();
 325
 326         return 0;
 327
 328 out_irq:
 329         free_percpu_irq(gt_ppi, gt_evt);
 330 out_free:
 331         free_percpu(gt_evt);
 332 out_clk:
 333         clk_disable_unprepare(gt_clk);
 334 out_unmap:
 335         iounmap(gt_base);
 336         WARN(err, "ARM Global timer register failed (%d)\n", err);
 337
 338         return err;
 339 }
 340
 341 /* Only tested on r2p2 and r3p0  */
 342 TIMER_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
 343                         global_timer_of_register);