linux/drivers/clocksource/arm_global_timer.c
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   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/err.h>
  20#include <linux/io.h>
  21#include <linux/of.h>
  22#include <linux/of_irq.h>
  23#include <linux/of_address.h>
  24#include <linux/sched_clock.h>
  25
  26#include <asm/cputype.h>
  27
  28#define GT_COUNTER0     0x00
  29#define GT_COUNTER1     0x04
  30
  31#define GT_CONTROL      0x08
  32#define GT_CONTROL_TIMER_ENABLE         BIT(0)  /* this bit is NOT banked */
  33#define GT_CONTROL_COMP_ENABLE          BIT(1)  /* banked */
  34#define GT_CONTROL_IRQ_ENABLE           BIT(2)  /* banked */
  35#define GT_CONTROL_AUTO_INC             BIT(3)  /* banked */
  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/*
  45 * We are expecting to be clocked by the ARM peripheral clock.
  46 *
  47 * Note: it is assumed we are using a prescaler value of zero, so this is
  48 * the units for all operations.
  49 */
  50static void __iomem *gt_base;
  51static unsigned long gt_clk_rate;
  52static int gt_ppi;
  53static struct clock_event_device __percpu *gt_evt;
  54
  55/*
  56 * To get the value from the Global Timer Counter register proceed as follows:
  57 * 1. Read the upper 32-bit timer counter register
  58 * 2. Read the lower 32-bit timer counter register
  59 * 3. Read the upper 32-bit timer counter register again. If the value is
  60 *  different to the 32-bit upper value read previously, go back to step 2.
  61 *  Otherwise the 64-bit timer counter value is correct.
  62 */
  63static u64 gt_counter_read(void)
  64{
  65        u64 counter;
  66        u32 lower;
  67        u32 upper, old_upper;
  68
  69        upper = readl_relaxed(gt_base + GT_COUNTER1);
  70        do {
  71                old_upper = upper;
  72                lower = readl_relaxed(gt_base + GT_COUNTER0);
  73                upper = readl_relaxed(gt_base + GT_COUNTER1);
  74        } while (upper != old_upper);
  75
  76        counter = upper;
  77        counter <<= 32;
  78        counter |= lower;
  79        return counter;
  80}
  81
  82/**
  83 * To ensure that updates to comparator value register do not set the
  84 * Interrupt Status Register proceed as follows:
  85 * 1. Clear the Comp Enable bit in the Timer Control Register.
  86 * 2. Write the lower 32-bit Comparator Value Register.
  87 * 3. Write the upper 32-bit Comparator Value Register.
  88 * 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit.
  89 */
  90static void gt_compare_set(unsigned long delta, int periodic)
  91{
  92        u64 counter = gt_counter_read();
  93        unsigned long ctrl;
  94
  95        counter += delta;
  96        ctrl = GT_CONTROL_TIMER_ENABLE;
  97        writel(ctrl, gt_base + GT_CONTROL);
  98        writel(lower_32_bits(counter), gt_base + GT_COMP0);
  99        writel(upper_32_bits(counter), gt_base + GT_COMP1);
 100
 101        if (periodic) {
 102                writel(delta, gt_base + GT_AUTO_INC);
 103                ctrl |= GT_CONTROL_AUTO_INC;
 104        }
 105
 106        ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
 107        writel(ctrl, gt_base + GT_CONTROL);
 108}
 109
 110static void gt_clockevent_set_mode(enum clock_event_mode mode,
 111                                   struct clock_event_device *clk)
 112{
 113        unsigned long ctrl;
 114
 115        switch (mode) {
 116        case CLOCK_EVT_MODE_PERIODIC:
 117                gt_compare_set(DIV_ROUND_CLOSEST(gt_clk_rate, HZ), 1);
 118                break;
 119        case CLOCK_EVT_MODE_ONESHOT:
 120        case CLOCK_EVT_MODE_UNUSED:
 121        case CLOCK_EVT_MODE_SHUTDOWN:
 122                ctrl = readl(gt_base + GT_CONTROL);
 123                ctrl &= ~(GT_CONTROL_COMP_ENABLE |
 124                                GT_CONTROL_IRQ_ENABLE | GT_CONTROL_AUTO_INC);
 125                writel(ctrl, gt_base + GT_CONTROL);
 126                break;
 127        default:
 128                break;
 129        }
 130}
 131
 132static int gt_clockevent_set_next_event(unsigned long evt,
 133                                        struct clock_event_device *unused)
 134{
 135        gt_compare_set(evt, 0);
 136        return 0;
 137}
 138
 139static irqreturn_t gt_clockevent_interrupt(int irq, void *dev_id)
 140{
 141        struct clock_event_device *evt = dev_id;
 142
 143        if (!(readl_relaxed(gt_base + GT_INT_STATUS) &
 144                                GT_INT_STATUS_EVENT_FLAG))
 145                return IRQ_NONE;
 146
 147        /**
 148         * ERRATA 740657( Global Timer can send 2 interrupts for
 149         * the same event in single-shot mode)
 150         * Workaround:
 151         *      Either disable single-shot mode.
 152         *      Or
 153         *      Modify the Interrupt Handler to avoid the
 154         *      offending sequence. This is achieved by clearing
 155         *      the Global Timer flag _after_ having incremented
 156         *      the Comparator register value to a higher value.
 157         */
 158        if (evt->mode == CLOCK_EVT_MODE_ONESHOT)
 159                gt_compare_set(ULONG_MAX, 0);
 160
 161        writel_relaxed(GT_INT_STATUS_EVENT_FLAG, gt_base + GT_INT_STATUS);
 162        evt->event_handler(evt);
 163
 164        return IRQ_HANDLED;
 165}
 166
 167static int gt_clockevents_init(struct clock_event_device *clk)
 168{
 169        int cpu = smp_processor_id();
 170
 171        clk->name = "arm_global_timer";
 172        clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
 173        clk->set_mode = gt_clockevent_set_mode;
 174        clk->set_next_event = gt_clockevent_set_next_event;
 175        clk->cpumask = cpumask_of(cpu);
 176        clk->rating = 300;
 177        clk->irq = gt_ppi;
 178        clockevents_config_and_register(clk, gt_clk_rate,
 179                                        1, 0xffffffff);
 180        enable_percpu_irq(clk->irq, IRQ_TYPE_NONE);
 181        return 0;
 182}
 183
 184static void gt_clockevents_stop(struct clock_event_device *clk)
 185{
 186        gt_clockevent_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
 187        disable_percpu_irq(clk->irq);
 188}
 189
 190static cycle_t gt_clocksource_read(struct clocksource *cs)
 191{
 192        return gt_counter_read();
 193}
 194
 195static struct clocksource gt_clocksource = {
 196        .name   = "arm_global_timer",
 197        .rating = 300,
 198        .read   = gt_clocksource_read,
 199        .mask   = CLOCKSOURCE_MASK(64),
 200        .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 201};
 202
 203#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
 204static u32 notrace gt_sched_clock_read(void)
 205{
 206        return gt_counter_read();
 207}
 208#endif
 209
 210static void __init gt_clocksource_init(void)
 211{
 212        writel(0, gt_base + GT_CONTROL);
 213        writel(0, gt_base + GT_COUNTER0);
 214        writel(0, gt_base + GT_COUNTER1);
 215        /* enables timer on all the cores */
 216        writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
 217
 218#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
 219        setup_sched_clock(gt_sched_clock_read, 32, gt_clk_rate);
 220#endif
 221        clocksource_register_hz(&gt_clocksource, gt_clk_rate);
 222}
 223
 224static int gt_cpu_notify(struct notifier_block *self, unsigned long action,
 225                         void *hcpu)
 226{
 227        switch (action & ~CPU_TASKS_FROZEN) {
 228        case CPU_STARTING:
 229                gt_clockevents_init(this_cpu_ptr(gt_evt));
 230                break;
 231        case CPU_DYING:
 232                gt_clockevents_stop(this_cpu_ptr(gt_evt));
 233                break;
 234        }
 235
 236        return NOTIFY_OK;
 237}
 238static struct notifier_block gt_cpu_nb = {
 239        .notifier_call = gt_cpu_notify,
 240};
 241
 242static void __init global_timer_of_register(struct device_node *np)
 243{
 244        struct clk *gt_clk;
 245        int err = 0;
 246
 247        /*
 248         * In r2p0 the comparators for each processor with the global timer
 249         * fire when the timer value is greater than or equal to. In previous
 250         * revisions the comparators fired when the timer value was equal to.
 251         */
 252        if ((read_cpuid_id() & 0xf0000f) < 0x200000) {
 253                pr_warn("global-timer: non support for this cpu version.\n");
 254                return;
 255        }
 256
 257        gt_ppi = irq_of_parse_and_map(np, 0);
 258        if (!gt_ppi) {
 259                pr_warn("global-timer: unable to parse irq\n");
 260                return;
 261        }
 262
 263        gt_base = of_iomap(np, 0);
 264        if (!gt_base) {
 265                pr_warn("global-timer: invalid base address\n");
 266                return;
 267        }
 268
 269        gt_clk = of_clk_get(np, 0);
 270        if (!IS_ERR(gt_clk)) {
 271                err = clk_prepare_enable(gt_clk);
 272                if (err)
 273                        goto out_unmap;
 274        } else {
 275                pr_warn("global-timer: clk not found\n");
 276                err = -EINVAL;
 277                goto out_unmap;
 278        }
 279
 280        gt_clk_rate = clk_get_rate(gt_clk);
 281        gt_evt = alloc_percpu(struct clock_event_device);
 282        if (!gt_evt) {
 283                pr_warn("global-timer: can't allocate memory\n");
 284                err = -ENOMEM;
 285                goto out_clk;
 286        }
 287
 288        err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt,
 289                                 "gt", gt_evt);
 290        if (err) {
 291                pr_warn("global-timer: can't register interrupt %d (%d)\n",
 292                        gt_ppi, err);
 293                goto out_free;
 294        }
 295
 296        err = register_cpu_notifier(&gt_cpu_nb);
 297        if (err) {
 298                pr_warn("global-timer: unable to register cpu notifier.\n");
 299                goto out_irq;
 300        }
 301
 302        /* Immediately configure the timer on the boot CPU */
 303        gt_clocksource_init();
 304        gt_clockevents_init(this_cpu_ptr(gt_evt));
 305
 306        return;
 307
 308out_irq:
 309        free_percpu_irq(gt_ppi, gt_evt);
 310out_free:
 311        free_percpu(gt_evt);
 312out_clk:
 313        clk_disable_unprepare(gt_clk);
 314out_unmap:
 315        iounmap(gt_base);
 316        WARN(err, "ARM Global timer register failed (%d)\n", err);
 317}
 318
 319/* Only tested on r2p2 and r3p0  */
 320CLOCKSOURCE_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
 321                        global_timer_of_register);
 322
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