arch/arm/kernel/smp_twd.c

   1 /*
   2  *  linux/arch/arm/kernel/smp_twd.c
   3  *
   4  *  Copyright (C) 2002 ARM Ltd.
   5  *  All Rights Reserved
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11 #include <linux/init.h>
  12 #include <linux/kernel.h>
  13 #include <linux/clk.h>
  14 #include <linux/cpu.h>
  15 #include <linux/delay.h>
  16 #include <linux/device.h>
  17 #include <linux/err.h>
  18 #include <linux/smp.h>
  19 #include <linux/jiffies.h>
  20 #include <linux/clockchips.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/io.h>
  23 #include <linux/of_irq.h>
  24 #include <linux/of_address.h>
  25
  26 #include <asm/smp_twd.h>
  27
  28 /* set up by the platform code */
  29 static void __iomem *twd_base;
  30
  31 static struct clk *twd_clk;
  32 static unsigned long twd_timer_rate;
  33 static DEFINE_PER_CPU(bool, percpu_setup_called);
  34
  35 static struct clock_event_device __percpu *twd_evt;
  36 static unsigned int twd_features =
  37                 CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
  38 static int twd_ppi;
  39
  40 static int twd_shutdown(struct clock_event_device *clk)
  41 {
  42         writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
  43         return 0;
  44 }
  45
  46 static int twd_set_oneshot(struct clock_event_device *clk)
  47 {
  48         /* period set, and timer enabled in 'next_event' hook */
  49         writel_relaxed(TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT,
  50                        twd_base + TWD_TIMER_CONTROL);
  51         return 0;
  52 }
  53
  54 static int twd_set_periodic(struct clock_event_device *clk)
  55 {
  56         unsigned long ctrl = TWD_TIMER_CONTROL_ENABLE |
  57                              TWD_TIMER_CONTROL_IT_ENABLE |
  58                              TWD_TIMER_CONTROL_PERIODIC;
  59
  60         writel_relaxed(DIV_ROUND_CLOSEST(twd_timer_rate, HZ),
  61                        twd_base + TWD_TIMER_LOAD);
  62         writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL);
  63         return 0;
  64 }
  65
  66 static int twd_set_next_event(unsigned long evt,
  67                         struct clock_event_device *unused)
  68 {
  69         unsigned long ctrl = readl_relaxed(twd_base + TWD_TIMER_CONTROL);
  70
  71         ctrl |= TWD_TIMER_CONTROL_ENABLE;
  72
  73         writel_relaxed(evt, twd_base + TWD_TIMER_COUNTER);
  74         writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL);
  75
  76         return 0;
  77 }
  78
  79 /*
  80  * local_timer_ack: checks for a local timer interrupt.
  81  *
  82  * If a local timer interrupt has occurred, acknowledge and return 1.
  83  * Otherwise, return 0.
  84  */
  85 static int twd_timer_ack(void)
  86 {
  87         if (readl_relaxed(twd_base + TWD_TIMER_INTSTAT)) {
  88                 writel_relaxed(1, twd_base + TWD_TIMER_INTSTAT);
  89                 return 1;
  90         }
  91
  92         return 0;
  93 }
  94
  95 static void twd_timer_stop(void)
  96 {
  97         struct clock_event_device *clk = raw_cpu_ptr(twd_evt);
  98
  99         twd_shutdown(clk);
 100         disable_percpu_irq(clk->irq);
 101 }
 102
 103 /*
 104  * Updates clockevent frequency when the cpu frequency changes.
 105  * Called on the cpu that is changing frequency with interrupts disabled.
 106  */
 107 static void twd_update_frequency(void *new_rate)
 108 {
 109         twd_timer_rate = *((unsigned long *) new_rate);
 110
 111         clockevents_update_freq(raw_cpu_ptr(twd_evt), twd_timer_rate);
 112 }
 113
 114 static int twd_rate_change(struct notifier_block *nb,
 115         unsigned long flags, void *data)
 116 {
 117         struct clk_notifier_data *cnd = data;
 118
 119         /*
 120          * The twd clock events must be reprogrammed to account for the new
 121          * frequency.  The timer is local to a cpu, so cross-call to the
 122          * changing cpu.
 123          */
 124         if (flags == POST_RATE_CHANGE)
 125                 on_each_cpu(twd_update_frequency,
 126                                   (void *)&cnd->new_rate, 1);
 127
 128         return NOTIFY_OK;
 129 }
 130
 131 static struct notifier_block twd_clk_nb = {
 132         .notifier_call = twd_rate_change,
 133 };
 134
 135 static int twd_clk_init(void)
 136 {
 137         if (twd_evt && raw_cpu_ptr(twd_evt) && !IS_ERR(twd_clk))
 138                 return clk_notifier_register(twd_clk, &twd_clk_nb);
 139
 140         return 0;
 141 }
 142 core_initcall(twd_clk_init);
 143
 144 static void twd_calibrate_rate(void)
 145 {
 146         unsigned long count;
 147         u64 waitjiffies;
 148
 149         /*
 150          * If this is the first time round, we need to work out how fast
 151          * the timer ticks
 152          */
 153         if (twd_timer_rate == 0) {
 154                 pr_info("Calibrating local timer... ");
 155
 156                 /* Wait for a tick to start */
 157                 waitjiffies = get_jiffies_64() + 1;
 158
 159                 while (get_jiffies_64() < waitjiffies)
 160                         udelay(10);
 161
 162                 /* OK, now the tick has started, let's get the timer going */
 163                 waitjiffies += 5;
 164
 165                                  /* enable, no interrupt or reload */
 166                 writel_relaxed(0x1, twd_base + TWD_TIMER_CONTROL);
 167
 168                                  /* maximum value */
 169                 writel_relaxed(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
 170
 171                 while (get_jiffies_64() < waitjiffies)
 172                         udelay(10);
 173
 174                 count = readl_relaxed(twd_base + TWD_TIMER_COUNTER);
 175
 176                 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
 177
 178                 pr_cont("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
 179                         (twd_timer_rate / 10000) % 100);
 180         }
 181 }
 182
 183 static irqreturn_t twd_handler(int irq, void *dev_id)
 184 {
 185         struct clock_event_device *evt = dev_id;
 186
 187         if (twd_timer_ack()) {
 188                 evt->event_handler(evt);
 189                 return IRQ_HANDLED;
 190         }
 191
 192         return IRQ_NONE;
 193 }
 194
 195 static void twd_get_clock(struct device_node *np)
 196 {
 197         int err;
 198
 199         if (np)
 200                 twd_clk = of_clk_get(np, 0);
 201         else
 202                 twd_clk = clk_get_sys("smp_twd", NULL);
 203
 204         if (IS_ERR(twd_clk)) {
 205                 pr_err("smp_twd: clock not found %d\n", (int) PTR_ERR(twd_clk));
 206                 return;
 207         }
 208
 209         err = clk_prepare_enable(twd_clk);
 210         if (err) {
 211                 pr_err("smp_twd: clock failed to prepare+enable: %d\n", err);
 212                 clk_put(twd_clk);
 213                 return;
 214         }
 215
 216         twd_timer_rate = clk_get_rate(twd_clk);
 217 }
 218
 219 /*
 220  * Setup the local clock events for a CPU.
 221  */
 222 static void twd_timer_setup(void)
 223 {
 224         struct clock_event_device *clk = raw_cpu_ptr(twd_evt);
 225         int cpu = smp_processor_id();
 226
 227         /*
 228          * If the basic setup for this CPU has been done before don't
 229          * bother with the below.
 230          */
 231         if (per_cpu(percpu_setup_called, cpu)) {
 232                 writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
 233                 clockevents_register_device(clk);
 234                 enable_percpu_irq(clk->irq, 0);
 235                 return;
 236         }
 237         per_cpu(percpu_setup_called, cpu) = true;
 238
 239         twd_calibrate_rate();
 240
 241         /*
 242          * The following is done once per CPU the first time .setup() is
 243          * called.
 244          */
 245         writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
 246
 247         clk->name = "local_timer";
 248         clk->features = twd_features;
 249         clk->rating = 350;
 250         clk->set_state_shutdown = twd_shutdown;
 251         clk->set_state_periodic = twd_set_periodic;
 252         clk->set_state_oneshot = twd_set_oneshot;
 253         clk->tick_resume = twd_shutdown;
 254         clk->set_next_event = twd_set_next_event;
 255         clk->irq = twd_ppi;
 256         clk->cpumask = cpumask_of(cpu);
 257
 258         clockevents_config_and_register(clk, twd_timer_rate,
 259                                         0xf, 0xffffffff);
 260         enable_percpu_irq(clk->irq, 0);
 261 }
 262
 263 static int twd_timer_starting_cpu(unsigned int cpu)
 264 {
 265         twd_timer_setup();
 266         return 0;
 267 }
 268
 269 static int twd_timer_dying_cpu(unsigned int cpu)
 270 {
 271         twd_timer_stop();
 272         return 0;
 273 }
 274
 275 static int __init twd_local_timer_common_register(struct device_node *np)
 276 {
 277         int err;
 278
 279         twd_evt = alloc_percpu(struct clock_event_device);
 280         if (!twd_evt) {
 281                 err = -ENOMEM;
 282                 goto out_free;
 283         }
 284
 285         err = request_percpu_irq(twd_ppi, twd_handler, "twd", twd_evt);
 286         if (err) {
 287                 pr_err("twd: can't register interrupt %d (%d)\n", twd_ppi, err);
 288                 goto out_free;
 289         }
 290
 291         cpuhp_setup_state_nocalls(CPUHP_AP_ARM_TWD_STARTING,
 292                                   "arm/timer/twd:starting",
 293                                   twd_timer_starting_cpu, twd_timer_dying_cpu);
 294
 295         twd_get_clock(np);
 296         if (!of_property_read_bool(np, "always-on"))
 297                 twd_features |= CLOCK_EVT_FEAT_C3STOP;
 298
 299         /*
 300          * Immediately configure the timer on the boot CPU, unless we need
 301          * jiffies to be incrementing to calibrate the rate in which case
 302          * setup the timer in late_time_init.
 303          */
 304         if (twd_timer_rate)
 305                 twd_timer_setup();
 306         else
 307                 late_time_init = twd_timer_setup;
 308
 309         return 0;
 310
 311 out_free:
 312         iounmap(twd_base);
 313         twd_base = NULL;
 314         free_percpu(twd_evt);
 315
 316         return err;
 317 }
 318
 319 static int __init twd_local_timer_of_register(struct device_node *np)
 320 {
 321         int err;
 322
 323         twd_ppi = irq_of_parse_and_map(np, 0);
 324         if (!twd_ppi) {
 325                 err = -EINVAL;
 326                 goto out;
 327         }
 328
 329         twd_base = of_iomap(np, 0);
 330         if (!twd_base) {
 331                 err = -ENOMEM;
 332                 goto out;
 333         }
 334
 335         err = twd_local_timer_common_register(np);
 336
 337 out:
 338         WARN(err, "twd_local_timer_of_register failed (%d)\n", err);
 339         return err;
 340 }
 341 TIMER_OF_DECLARE(arm_twd_a9, "arm,cortex-a9-twd-timer", twd_local_timer_of_register);
 342 TIMER_OF_DECLARE(arm_twd_a5, "arm,cortex-a5-twd-timer", twd_local_timer_of_register);
 343 TIMER_OF_DECLARE(arm_twd_11mp, "arm,arm11mp-twd-timer", twd_local_timer_of_register);