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/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  */
  50 static void __iomem *gt_base;
  51 static unsigned long gt_clk_rate;
  52 static int gt_ppi;
  53 static 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  */
  63 static u64 notrace _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 static u64 gt_counter_read(void)
  83 {
  84         return _gt_counter_read();
  85 }
  86
  87 /**
  88  * To ensure that updates to comparator value register do not set the
  89  * Interrupt Status Register proceed as follows:
  90  * 1. Clear the Comp Enable bit in the Timer Control Register.
  91  * 2. Write the lower 32-bit Comparator Value Register.
  92  * 3. Write the upper 32-bit Comparator Value Register.
  93  * 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit.
  94  */
  95 static void gt_compare_set(unsigned long delta, int periodic)
  96 {
  97         u64 counter = gt_counter_read();
  98         unsigned long ctrl;
  99
 100         counter += delta;
 101         ctrl = GT_CONTROL_TIMER_ENABLE;
 102         writel(ctrl, gt_base + GT_CONTROL);
 103         writel(lower_32_bits(counter), gt_base + GT_COMP0);
 104         writel(upper_32_bits(counter), gt_base + GT_COMP1);
 105
 106         if (periodic) {
 107                 writel(delta, gt_base + GT_AUTO_INC);
 108                 ctrl |= GT_CONTROL_AUTO_INC;
 109         }
 110
 111         ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
 112         writel(ctrl, gt_base + GT_CONTROL);
 113 }
 114
 115 static int gt_clockevent_shutdown(struct clock_event_device *evt)
 116 {
 117         unsigned long ctrl;
 118
 119         ctrl = readl(gt_base + GT_CONTROL);
 120         ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE |
 121                   GT_CONTROL_AUTO_INC);
 122         writel(ctrl, gt_base + GT_CONTROL);
 123         return 0;
 124 }
 125
 126 static int gt_clockevent_set_periodic(struct clock_event_device *evt)
 127 {
 128         gt_compare_set(DIV_ROUND_CLOSEST(gt_clk_rate, HZ), 1);
 129         return 0;
 130 }
 131
 132 static 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
 139 static 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 (clockevent_state_oneshot(evt))
 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
 167 static 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                 CLOCK_EVT_FEAT_PERCPU;
 174         clk->set_state_shutdown = gt_clockevent_shutdown;
 175         clk->set_state_periodic = gt_clockevent_set_periodic;
 176         clk->set_state_oneshot = gt_clockevent_shutdown;
 177         clk->set_next_event = gt_clockevent_set_next_event;
 178         clk->cpumask = cpumask_of(cpu);
 179         clk->rating = 300;
 180         clk->irq = gt_ppi;
 181         clockevents_config_and_register(clk, gt_clk_rate,
 182                                         1, 0xffffffff);
 183         enable_percpu_irq(clk->irq, IRQ_TYPE_NONE);
 184         return 0;
 185 }
 186
 187 static void gt_clockevents_stop(struct clock_event_device *clk)
 188 {
 189         gt_clockevent_shutdown(clk);
 190         disable_percpu_irq(clk->irq);
 191 }
 192
 193 static cycle_t gt_clocksource_read(struct clocksource *cs)
 194 {
 195         return gt_counter_read();
 196 }
 197
 198 static struct clocksource gt_clocksource = {
 199         .name   = "arm_global_timer",
 200         .rating = 300,
 201         .read   = gt_clocksource_read,
 202         .mask   = CLOCKSOURCE_MASK(64),
 203         .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 204 };
 205
 206 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
 207 static u64 notrace gt_sched_clock_read(void)
 208 {
 209         return _gt_counter_read();
 210 }
 211 #endif
 212
 213 static void __init gt_clocksource_init(void)
 214 {
 215         writel(0, gt_base + GT_CONTROL);
 216         writel(0, gt_base + GT_COUNTER0);
 217         writel(0, gt_base + GT_COUNTER1);
 218         /* enables timer on all the cores */
 219         writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
 220
 221 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
 222         sched_clock_register(gt_sched_clock_read, 64, gt_clk_rate);
 223 #endif
 224         clocksource_register_hz(&gt_clocksource, gt_clk_rate);
 225 }
 226
 227 static int gt_cpu_notify(struct notifier_block *self, unsigned long action,
 228                          void *hcpu)
 229 {
 230         switch (action & ~CPU_TASKS_FROZEN) {
 231         case CPU_STARTING:
 232                 gt_clockevents_init(this_cpu_ptr(gt_evt));
 233                 break;
 234         case CPU_DYING:
 235                 gt_clockevents_stop(this_cpu_ptr(gt_evt));
 236                 break;
 237         }
 238
 239         return NOTIFY_OK;
 240 }
 241 static struct notifier_block gt_cpu_nb = {
 242         .notifier_call = gt_cpu_notify,
 243 };
 244
 245 static void __init global_timer_of_register(struct device_node *np)
 246 {
 247         struct clk *gt_clk;
 248         int err = 0;
 249
 250         /*
 251          * In A9 r2p0 the comparators for each processor with the global timer
 252          * fire when the timer value is greater than or equal to. In previous
 253          * revisions the comparators fired when the timer value was equal to.
 254          */
 255         if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9
 256             && (read_cpuid_id() & 0xf0000f) < 0x200000) {
 257                 pr_warn("global-timer: non support for this cpu version.\n");
 258                 return;
 259         }
 260
 261         gt_ppi = irq_of_parse_and_map(np, 0);
 262         if (!gt_ppi) {
 263                 pr_warn("global-timer: unable to parse irq\n");
 264                 return;
 265         }
 266
 267         gt_base = of_iomap(np, 0);
 268         if (!gt_base) {
 269                 pr_warn("global-timer: invalid base address\n");
 270                 return;
 271         }
 272
 273         gt_clk = of_clk_get(np, 0);
 274         if (!IS_ERR(gt_clk)) {
 275                 err = clk_prepare_enable(gt_clk);
 276                 if (err)
 277                         goto out_unmap;
 278         } else {
 279                 pr_warn("global-timer: clk not found\n");
 280                 err = -EINVAL;
 281                 goto out_unmap;
 282         }
 283
 284         gt_clk_rate = clk_get_rate(gt_clk);
 285         gt_evt = alloc_percpu(struct clock_event_device);
 286         if (!gt_evt) {
 287                 pr_warn("global-timer: can't allocate memory\n");
 288                 err = -ENOMEM;
 289                 goto out_clk;
 290         }
 291
 292         err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt,
 293                                  "gt", gt_evt);
 294         if (err) {
 295                 pr_warn("global-timer: can't register interrupt %d (%d)\n",
 296                         gt_ppi, err);
 297                 goto out_free;
 298         }
 299
 300         err = register_cpu_notifier(&gt_cpu_nb);
 301         if (err) {
 302                 pr_warn("global-timer: unable to register cpu notifier.\n");
 303                 goto out_irq;
 304         }
 305
 306         /* Immediately configure the timer on the boot CPU */
 307         gt_clocksource_init();
 308         gt_clockevents_init(this_cpu_ptr(gt_evt));
 309
 310         return;
 311
 312 out_irq:
 313         free_percpu_irq(gt_ppi, gt_evt);
 314 out_free:
 315         free_percpu(gt_evt);
 316 out_clk:
 317         clk_disable_unprepare(gt_clk);
 318 out_unmap:
 319         iounmap(gt_base);
 320         WARN(err, "ARM Global timer register failed (%d)\n", err);
 321 }
 322
 323 /* Only tested on r2p2 and r3p0  */
 324 CLOCKSOURCE_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
 325                         global_timer_of_register);