arch/arm/kernel/smp_twd.c

   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         disable_percpu_irq(clk->irq);
  97 }
  98
  99 /*
 100  * Updates clockevent frequency when the cpu frequency changes.
 101  * Called on the cpu that is changing frequency with interrupts disabled.
 102  */
 103 static void twd_update_frequency(void *new_rate)
 104 {
 105         twd_timer_rate = *((unsigned long *) new_rate);
 106
 107         clockevents_update_freq(raw_cpu_ptr(twd_evt), twd_timer_rate);
 108 }
 109
 110 static int twd_rate_change(struct notifier_block *nb,
 111         unsigned long flags, void *data)
 112 {
 113         struct clk_notifier_data *cnd = data;
 114
 115         /*
 116          * The twd clock events must be reprogrammed to account for the new
 117          * frequency.  The timer is local to a cpu, so cross-call to the
 118          * changing cpu.
 119          */
 120         if (flags == POST_RATE_CHANGE)
 121                 on_each_cpu(twd_update_frequency,
 122                                   (void *)&cnd->new_rate, 1);
 123
 124         return NOTIFY_OK;
 125 }
 126
 127 static struct notifier_block twd_clk_nb = {
 128         .notifier_call = twd_rate_change,
 129 };
 130
 131 static int twd_clk_init(void)
 132 {
 133         if (twd_evt && raw_cpu_ptr(twd_evt) && !IS_ERR(twd_clk))
 134                 return clk_notifier_register(twd_clk, &twd_clk_nb);
 135
 136         return 0;
 137 }
 138 core_initcall(twd_clk_init);
 139
 140 static void twd_calibrate_rate(void)
 141 {
 142         unsigned long count;
 143         u64 waitjiffies;
 144
 145         /*
 146          * If this is the first time round, we need to work out how fast
 147          * the timer ticks
 148          */
 149         if (twd_timer_rate == 0) {
 150                 pr_info("Calibrating local timer... ");
 151
 152                 /* Wait for a tick to start */
 153                 waitjiffies = get_jiffies_64() + 1;
 154
 155                 while (get_jiffies_64() < waitjiffies)
 156                         udelay(10);
 157
 158                 /* OK, now the tick has started, let's get the timer going */
 159                 waitjiffies += 5;
 160
 161                                  /* enable, no interrupt or reload */
 162                 writel_relaxed(0x1, twd_base + TWD_TIMER_CONTROL);
 163
 164                                  /* maximum value */
 165                 writel_relaxed(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
 166
 167                 while (get_jiffies_64() < waitjiffies)
 168                         udelay(10);
 169
 170                 count = readl_relaxed(twd_base + TWD_TIMER_COUNTER);
 171
 172                 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
 173
 174                 pr_cont("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
 175                         (twd_timer_rate / 10000) % 100);
 176         }
 177 }
 178
 179 static irqreturn_t twd_handler(int irq, void *dev_id)
 180 {
 181         struct clock_event_device *evt = dev_id;
 182
 183         if (twd_timer_ack()) {
 184                 evt->event_handler(evt);
 185                 return IRQ_HANDLED;
 186         }
 187
 188         return IRQ_NONE;
 189 }
 190
 191 static void twd_get_clock(struct device_node *np)
 192 {
 193         int err;
 194
 195         if (np)
 196                 twd_clk = of_clk_get(np, 0);
 197         else
 198                 twd_clk = clk_get_sys("smp_twd", NULL);
 199
 200         if (IS_ERR(twd_clk)) {
 201                 pr_err("smp_twd: clock not found %d\n", (int) PTR_ERR(twd_clk));
 202                 return;
 203         }
 204
 205         err = clk_prepare_enable(twd_clk);
 206         if (err) {
 207                 pr_err("smp_twd: clock failed to prepare+enable: %d\n", err);
 208                 clk_put(twd_clk);
 209                 return;
 210         }
 211
 212         twd_timer_rate = clk_get_rate(twd_clk);
 213 }
 214
 215 /*
 216  * Setup the local clock events for a CPU.
 217  */
 218 static void twd_timer_setup(void)
 219 {
 220         struct clock_event_device *clk = raw_cpu_ptr(twd_evt);
 221         int cpu = smp_processor_id();
 222
 223         /*
 224          * If the basic setup for this CPU has been done before don't
 225          * bother with the below.
 226          */
 227         if (per_cpu(percpu_setup_called, cpu)) {
 228                 writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
 229                 clockevents_register_device(clk);
 230                 enable_percpu_irq(clk->irq, 0);
 231                 return;
 232         }
 233         per_cpu(percpu_setup_called, cpu) = true;
 234
 235         twd_calibrate_rate();
 236
 237         /*
 238          * The following is done once per CPU the first time .setup() is
 239          * called.
 240          */
 241         writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
 242
 243         clk->name = "local_timer";
 244         clk->features = twd_features;
 245         clk->rating = 350;
 246         clk->set_state_shutdown = twd_shutdown;
 247         clk->set_state_periodic = twd_set_periodic;
 248         clk->set_state_oneshot = twd_set_oneshot;
 249         clk->tick_resume = twd_shutdown;
 250         clk->set_next_event = twd_set_next_event;
 251         clk->irq = twd_ppi;
 252         clk->cpumask = cpumask_of(cpu);
 253
 254         clockevents_config_and_register(clk, twd_timer_rate,
 255                                         0xf, 0xffffffff);
 256         enable_percpu_irq(clk->irq, 0);
 257 }
 258
 259 static int twd_timer_starting_cpu(unsigned int cpu)
 260 {
 261         twd_timer_setup();
 262         return 0;
 263 }
 264
 265 static int twd_timer_dying_cpu(unsigned int cpu)
 266 {
 267         twd_timer_stop();
 268         return 0;
 269 }
 270
 271 static int __init twd_local_timer_common_register(struct device_node *np)
 272 {
 273         int err;
 274
 275         twd_evt = alloc_percpu(struct clock_event_device);
 276         if (!twd_evt) {
 277                 err = -ENOMEM;
 278                 goto out_free;
 279         }
 280
 281         err = request_percpu_irq(twd_ppi, twd_handler, "twd", twd_evt);
 282         if (err) {
 283                 pr_err("twd: can't register interrupt %d (%d)\n", twd_ppi, err);
 284                 goto out_free;
 285         }
 286
 287         cpuhp_setup_state_nocalls(CPUHP_AP_ARM_TWD_STARTING,
 288                                   "arm/timer/twd:starting",
 289                                   twd_timer_starting_cpu, twd_timer_dying_cpu);
 290
 291         twd_get_clock(np);
 292         if (!of_property_read_bool(np, "always-on"))
 293                 twd_features |= CLOCK_EVT_FEAT_C3STOP;
 294
 295         /*
 296          * Immediately configure the timer on the boot CPU, unless we need
 297          * jiffies to be incrementing to calibrate the rate in which case
 298          * setup the timer in late_time_init.
 299          */
 300         if (twd_timer_rate)
 301                 twd_timer_setup();
 302         else
 303                 late_time_init = twd_timer_setup;
 304
 305         return 0;
 306
 307 out_free:
 308         iounmap(twd_base);
 309         twd_base = NULL;
 310         free_percpu(twd_evt);
 311
 312         return err;
 313 }
 314
 315 static int __init twd_local_timer_of_register(struct device_node *np)
 316 {
 317         int err;
 318
 319         twd_ppi = irq_of_parse_and_map(np, 0);
 320         if (!twd_ppi) {
 321                 err = -EINVAL;
 322                 goto out;
 323         }
 324
 325         twd_base = of_iomap(np, 0);
 326         if (!twd_base) {
 327                 err = -ENOMEM;
 328                 goto out;
 329         }
 330
 331         err = twd_local_timer_common_register(np);
 332
 333 out:
 334         WARN(err, "twd_local_timer_of_register failed (%d)\n", err);
 335         return err;
 336 }
 337 TIMER_OF_DECLARE(arm_twd_a9, "arm,cortex-a9-twd-timer", twd_local_timer_of_register);
 338 TIMER_OF_DECLARE(arm_twd_a5, "arm,cortex-a5-twd-timer", twd_local_timer_of_register);
 339 TIMER_OF_DECLARE(arm_twd_11mp, "arm,arm11mp-twd-timer", twd_local_timer_of_register);