root/arch/arm/kernel/smp_twd.c

DEFINITIONS

1. twd_shutdown
2. twd_set_oneshot
3. twd_set_periodic
4. twd_set_next_event
5. twd_timer_ack
6. twd_timer_stop
7. twd_update_frequency
8. twd_rate_change
9. twd_clk_init
10. twd_calibrate_rate
11. twd_handler
12. twd_get_clock
13. twd_timer_setup
14. twd_timer_starting_cpu
15. twd_timer_dying_cpu
16. twd_local_timer_common_register
17. twd_local_timer_of_register

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/arch/arm/kernel/smp_twd.c
   4  *
   5  *  Copyright (C) 2002 ARM Ltd.
   6  *  All Rights Reserved
   7  */
   8 #include <linux/init.h>
   9 #include <linux/kernel.h>
  10 #include <linux/clk.h>
  11 #include <linux/cpu.h>
  12 #include <linux/delay.h>
  13 #include <linux/device.h>
  14 #include <linux/err.h>
  15 #include <linux/smp.h>
  16 #include <linux/jiffies.h>
  17 #include <linux/clockchips.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/io.h>
  20 #include <linux/of_irq.h>
  21 #include <linux/of_address.h>
  22 
  23 #include <asm/smp_twd.h>
  24 
  25 /* set up by the platform code */
  26 static void __iomem *twd_base;
  27 
  28 static struct clk *twd_clk;
  29 static unsigned long twd_timer_rate;
  30 static DEFINE_PER_CPU(bool, percpu_setup_called);
  31 
  32 static struct clock_event_device __percpu *twd_evt;
  33 static unsigned int twd_features =
  34                 CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
  35 static int twd_ppi;
  36 
  37 static int twd_shutdown(struct clock_event_device *clk)
  38 {
  39         writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
  40         return 0;
  41 }
  42 
  43 static int twd_set_oneshot(struct clock_event_device *clk)
  44 {
  45         /* period set, and timer enabled in 'next_event' hook */
  46         writel_relaxed(TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT,
  47                        twd_base + TWD_TIMER_CONTROL);
  48         return 0;
  49 }
  50 
  51 static int twd_set_periodic(struct clock_event_device *clk)
  52 {
  53         unsigned long ctrl = TWD_TIMER_CONTROL_ENABLE |
  54                              TWD_TIMER_CONTROL_IT_ENABLE |
  55                              TWD_TIMER_CONTROL_PERIODIC;
  56 
  57         writel_relaxed(DIV_ROUND_CLOSEST(twd_timer_rate, HZ),
  58                        twd_base + TWD_TIMER_LOAD);
  59         writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL);
  60         return 0;
  61 }
  62 
  63 static int twd_set_next_event(unsigned long evt,
  64                         struct clock_event_device *unused)
  65 {
  66         unsigned long ctrl = readl_relaxed(twd_base + TWD_TIMER_CONTROL);
  67 
  68         ctrl |= TWD_TIMER_CONTROL_ENABLE;
  69 
  70         writel_relaxed(evt, twd_base + TWD_TIMER_COUNTER);
  71         writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL);
  72 
  73         return 0;
  74 }
  75 
  76 /*
  77  * local_timer_ack: checks for a local timer interrupt.
  78  *
  79  * If a local timer interrupt has occurred, acknowledge and return 1.
  80  * Otherwise, return 0.
  81  */
  82 static int twd_timer_ack(void)
  83 {
  84         if (readl_relaxed(twd_base + TWD_TIMER_INTSTAT)) {
  85                 writel_relaxed(1, twd_base + TWD_TIMER_INTSTAT);
  86                 return 1;
  87         }
  88 
  89         return 0;
  90 }
  91 
  92 static void twd_timer_stop(void)
  93 {
  94         struct clock_event_device *clk = raw_cpu_ptr(twd_evt);
  95 
  96         twd_shutdown(clk);
  97         disable_percpu_irq(clk->irq);
  98 }
  99 
 100 /*
 101  * Updates clockevent frequency when the cpu frequency changes.
 102  * Called on the cpu that is changing frequency with interrupts disabled.
 103  */
 104 static void twd_update_frequency(void *new_rate)
 105 {
 106         twd_timer_rate = *((unsigned long *) new_rate);
 107 
 108         clockevents_update_freq(raw_cpu_ptr(twd_evt), twd_timer_rate);
 109 }
 110 
 111 static int twd_rate_change(struct notifier_block *nb,
 112         unsigned long flags, void *data)
 113 {
 114         struct clk_notifier_data *cnd = data;
 115 
 116         /*
 117          * The twd clock events must be reprogrammed to account for the new
 118          * frequency.  The timer is local to a cpu, so cross-call to the
 119          * changing cpu.
 120          */
 121         if (flags == POST_RATE_CHANGE)
 122                 on_each_cpu(twd_update_frequency,
 123                                   (void *)&cnd->new_rate, 1);
 124 
 125         return NOTIFY_OK;
 126 }
 127 
 128 static struct notifier_block twd_clk_nb = {
 129         .notifier_call = twd_rate_change,
 130 };
 131 
 132 static int twd_clk_init(void)
 133 {
 134         if (twd_evt && raw_cpu_ptr(twd_evt) && !IS_ERR(twd_clk))
 135                 return clk_notifier_register(twd_clk, &twd_clk_nb);
 136 
 137         return 0;
 138 }
 139 core_initcall(twd_clk_init);
 140 
 141 static void twd_calibrate_rate(void)
 142 {
 143         unsigned long count;
 144         u64 waitjiffies;
 145 
 146         /*
 147          * If this is the first time round, we need to work out how fast
 148          * the timer ticks
 149          */
 150         if (twd_timer_rate == 0) {
 151                 pr_info("Calibrating local timer... ");
 152 
 153                 /* Wait for a tick to start */
 154                 waitjiffies = get_jiffies_64() + 1;
 155 
 156                 while (get_jiffies_64() < waitjiffies)
 157                         udelay(10);
 158 
 159                 /* OK, now the tick has started, let's get the timer going */
 160                 waitjiffies += 5;
 161 
 162                                  /* enable, no interrupt or reload */
 163                 writel_relaxed(0x1, twd_base + TWD_TIMER_CONTROL);
 164 
 165                                  /* maximum value */
 166                 writel_relaxed(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
 167 
 168                 while (get_jiffies_64() < waitjiffies)
 169                         udelay(10);
 170 
 171                 count = readl_relaxed(twd_base + TWD_TIMER_COUNTER);
 172 
 173                 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
 174 
 175                 pr_cont("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
 176                         (twd_timer_rate / 10000) % 100);
 177         }
 178 }
 179 
 180 static irqreturn_t twd_handler(int irq, void *dev_id)
 181 {
 182         struct clock_event_device *evt = dev_id;
 183 
 184         if (twd_timer_ack()) {
 185                 evt->event_handler(evt);
 186                 return IRQ_HANDLED;
 187         }
 188 
 189         return IRQ_NONE;
 190 }
 191 
 192 static void twd_get_clock(struct device_node *np)
 193 {
 194         int err;
 195 
 196         if (np)
 197                 twd_clk = of_clk_get(np, 0);
 198         else
 199                 twd_clk = clk_get_sys("smp_twd", NULL);
 200 
 201         if (IS_ERR(twd_clk)) {
 202                 pr_err("smp_twd: clock not found %d\n", (int) PTR_ERR(twd_clk));
 203                 return;
 204         }
 205 
 206         err = clk_prepare_enable(twd_clk);
 207         if (err) {
 208                 pr_err("smp_twd: clock failed to prepare+enable: %d\n", err);
 209                 clk_put(twd_clk);
 210                 return;
 211         }
 212 
 213         twd_timer_rate = clk_get_rate(twd_clk);
 214 }
 215 
 216 /*
 217  * Setup the local clock events for a CPU.
 218  */
 219 static void twd_timer_setup(void)
 220 {
 221         struct clock_event_device *clk = raw_cpu_ptr(twd_evt);
 222         int cpu = smp_processor_id();
 223 
 224         /*
 225          * If the basic setup for this CPU has been done before don't
 226          * bother with the below.
 227          */
 228         if (per_cpu(percpu_setup_called, cpu)) {
 229                 writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
 230                 clockevents_register_device(clk);
 231                 enable_percpu_irq(clk->irq, 0);
 232                 return;
 233         }
 234         per_cpu(percpu_setup_called, cpu) = true;
 235 
 236         twd_calibrate_rate();
 237 
 238         /*
 239          * The following is done once per CPU the first time .setup() is
 240          * called.
 241          */
 242         writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
 243 
 244         clk->name = "local_timer";
 245         clk->features = twd_features;
 246         clk->rating = 350;
 247         clk->set_state_shutdown = twd_shutdown;
 248         clk->set_state_periodic = twd_set_periodic;
 249         clk->set_state_oneshot = twd_set_oneshot;
 250         clk->tick_resume = twd_shutdown;
 251         clk->set_next_event = twd_set_next_event;
 252         clk->irq = twd_ppi;
 253         clk->cpumask = cpumask_of(cpu);
 254 
 255         clockevents_config_and_register(clk, twd_timer_rate,
 256                                         0xf, 0xffffffff);
 257         enable_percpu_irq(clk->irq, 0);
 258 }
 259 
 260 static int twd_timer_starting_cpu(unsigned int cpu)
 261 {
 262         twd_timer_setup();
 263         return 0;
 264 }
 265 
 266 static int twd_timer_dying_cpu(unsigned int cpu)
 267 {
 268         twd_timer_stop();
 269         return 0;
 270 }
 271 
 272 static int __init twd_local_timer_common_register(struct device_node *np)
 273 {
 274         int err;
 275 
 276         twd_evt = alloc_percpu(struct clock_event_device);
 277         if (!twd_evt) {
 278                 err = -ENOMEM;
 279                 goto out_free;
 280         }
 281 
 282         err = request_percpu_irq(twd_ppi, twd_handler, "twd", twd_evt);
 283         if (err) {
 284                 pr_err("twd: can't register interrupt %d (%d)\n", twd_ppi, err);
 285                 goto out_free;
 286         }
 287 
 288         cpuhp_setup_state_nocalls(CPUHP_AP_ARM_TWD_STARTING,
 289                                   "arm/timer/twd:starting",
 290                                   twd_timer_starting_cpu, twd_timer_dying_cpu);
 291 
 292         twd_get_clock(np);
 293         if (!of_property_read_bool(np, "always-on"))
 294                 twd_features |= CLOCK_EVT_FEAT_C3STOP;
 295 
 296         /*
 297          * Immediately configure the timer on the boot CPU, unless we need
 298          * jiffies to be incrementing to calibrate the rate in which case
 299          * setup the timer in late_time_init.
 300          */
 301         if (twd_timer_rate)
 302                 twd_timer_setup();
 303         else
 304                 late_time_init = twd_timer_setup;
 305 
 306         return 0;
 307 
 308 out_free:
 309         iounmap(twd_base);
 310         twd_base = NULL;
 311         free_percpu(twd_evt);
 312 
 313         return err;
 314 }
 315 
 316 static int __init twd_local_timer_of_register(struct device_node *np)
 317 {
 318         int err;
 319 
 320         twd_ppi = irq_of_parse_and_map(np, 0);
 321         if (!twd_ppi) {
 322                 err = -EINVAL;
 323                 goto out;
 324         }
 325 
 326         twd_base = of_iomap(np, 0);
 327         if (!twd_base) {
 328                 err = -ENOMEM;
 329                 goto out;
 330         }
 331 
 332         err = twd_local_timer_common_register(np);
 333 
 334 out:
 335         WARN(err, "twd_local_timer_of_register failed (%d)\n", err);
 336         return err;
 337 }
 338 TIMER_OF_DECLARE(arm_twd_a9, "arm,cortex-a9-twd-timer", twd_local_timer_of_register);
 339 TIMER_OF_DECLARE(arm_twd_a5, "arm,cortex-a5-twd-timer", twd_local_timer_of_register);
 340 TIMER_OF_DECLARE(arm_twd_11mp, "arm,arm11mp-twd-timer", twd_local_timer_of_register);