arm/kernel/smp_twd.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  *  linux/arch/arm/kernel/smp_twd.c
0004  *
0005  *  Copyright (C) 2002 ARM Ltd.
0006  *  All Rights Reserved
0007  */
0008 #include <linux/init.h>
0009 #include <linux/kernel.h>
0010 #include <linux/clk.h>
0011 #include <linux/cpu.h>
0012 #include <linux/delay.h>
0013 #include <linux/device.h>
0014 #include <linux/err.h>
0015 #include <linux/smp.h>
0016 #include <linux/jiffies.h>
0017 #include <linux/clockchips.h>
0018 #include <linux/interrupt.h>
0019 #include <linux/io.h>
0020 #include <linux/of_irq.h>
0021 #include <linux/of_address.h>
0022
0023 #include <asm/smp_twd.h>
0024
0025 /* set up by the platform code */
0026 static void __iomem *twd_base;
0027
0028 static struct clk *twd_clk;
0029 static unsigned long twd_timer_rate;
0030 static DEFINE_PER_CPU(bool, percpu_setup_called);
0031
0032 static struct clock_event_device __percpu *twd_evt;
0033 static unsigned int twd_features =
0034         CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
0035 static int twd_ppi;
0036
0037 static int twd_shutdown(struct clock_event_device *clk)
0038 {
0039     writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
0040     return 0;
0041 }
0042
0043 static int twd_set_oneshot(struct clock_event_device *clk)
0044 {
0045     /* period set, and timer enabled in 'next_event' hook */
0046     writel_relaxed(TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT,
0047                twd_base + TWD_TIMER_CONTROL);
0048     return 0;
0049 }
0050
0051 static int twd_set_periodic(struct clock_event_device *clk)
0052 {
0053     unsigned long ctrl = TWD_TIMER_CONTROL_ENABLE |
0054                  TWD_TIMER_CONTROL_IT_ENABLE |
0055                  TWD_TIMER_CONTROL_PERIODIC;
0056
0057     writel_relaxed(DIV_ROUND_CLOSEST(twd_timer_rate, HZ),
0058                twd_base + TWD_TIMER_LOAD);
0059     writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL);
0060     return 0;
0061 }
0062
0063 static int twd_set_next_event(unsigned long evt,
0064             struct clock_event_device *unused)
0065 {
0066     unsigned long ctrl = readl_relaxed(twd_base + TWD_TIMER_CONTROL);
0067
0068     ctrl |= TWD_TIMER_CONTROL_ENABLE;
0069
0070     writel_relaxed(evt, twd_base + TWD_TIMER_COUNTER);
0071     writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL);
0072
0073     return 0;
0074 }
0075
0076 /*
0077  * local_timer_ack: checks for a local timer interrupt.
0078  *
0079  * If a local timer interrupt has occurred, acknowledge and return 1.
0080  * Otherwise, return 0.
0081  */
0082 static int twd_timer_ack(void)
0083 {
0084     if (readl_relaxed(twd_base + TWD_TIMER_INTSTAT)) {
0085         writel_relaxed(1, twd_base + TWD_TIMER_INTSTAT);
0086         return 1;
0087     }
0088
0089     return 0;
0090 }
0091
0092 static void twd_timer_stop(void)
0093 {
0094     struct clock_event_device *clk = raw_cpu_ptr(twd_evt);
0095
0096     twd_shutdown(clk);
0097     disable_percpu_irq(clk->irq);
0098 }
0099
0100 /*
0101  * Updates clockevent frequency when the cpu frequency changes.
0102  * Called on the cpu that is changing frequency with interrupts disabled.
0103  */
0104 static void twd_update_frequency(void *new_rate)
0105 {
0106     twd_timer_rate = *((unsigned long *) new_rate);
0107
0108     clockevents_update_freq(raw_cpu_ptr(twd_evt), twd_timer_rate);
0109 }
0110
0111 static int twd_rate_change(struct notifier_block *nb,
0112     unsigned long flags, void *data)
0113 {
0114     struct clk_notifier_data *cnd = data;
0115
0116     /*
0117      * The twd clock events must be reprogrammed to account for the new
0118      * frequency.  The timer is local to a cpu, so cross-call to the
0119      * changing cpu.
0120      */
0121     if (flags == POST_RATE_CHANGE)
0122         on_each_cpu(twd_update_frequency,
0123                   (void *)&cnd->new_rate, 1);
0124
0125     return NOTIFY_OK;
0126 }
0127
0128 static struct notifier_block twd_clk_nb = {
0129     .notifier_call = twd_rate_change,
0130 };
0131
0132 static int twd_clk_init(void)
0133 {
0134     if (twd_evt && raw_cpu_ptr(twd_evt) && !IS_ERR(twd_clk))
0135         return clk_notifier_register(twd_clk, &twd_clk_nb);
0136
0137     return 0;
0138 }
0139 core_initcall(twd_clk_init);
0140
0141 static void twd_calibrate_rate(void)
0142 {
0143     unsigned long count;
0144     u64 waitjiffies;
0145
0146     /*
0147      * If this is the first time round, we need to work out how fast
0148      * the timer ticks
0149      */
0150     if (twd_timer_rate == 0) {
0151         pr_info("Calibrating local timer... ");
0152
0153         /* Wait for a tick to start */
0154         waitjiffies = get_jiffies_64() + 1;
0155
0156         while (get_jiffies_64() < waitjiffies)
0157             udelay(10);
0158
0159         /* OK, now the tick has started, let's get the timer going */
0160         waitjiffies += 5;
0161
0162                  /* enable, no interrupt or reload */
0163         writel_relaxed(0x1, twd_base + TWD_TIMER_CONTROL);
0164
0165                  /* maximum value */
0166         writel_relaxed(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
0167
0168         while (get_jiffies_64() < waitjiffies)
0169             udelay(10);
0170
0171         count = readl_relaxed(twd_base + TWD_TIMER_COUNTER);
0172
0173         twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
0174
0175         pr_cont("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
0176             (twd_timer_rate / 10000) % 100);
0177     }
0178 }
0179
0180 static irqreturn_t twd_handler(int irq, void *dev_id)
0181 {
0182     struct clock_event_device *evt = dev_id;
0183
0184     if (twd_timer_ack()) {
0185         evt->event_handler(evt);
0186         return IRQ_HANDLED;
0187     }
0188
0189     return IRQ_NONE;
0190 }
0191
0192 static void twd_get_clock(struct device_node *np)
0193 {
0194     int err;
0195
0196     if (np)
0197         twd_clk = of_clk_get(np, 0);
0198     else
0199         twd_clk = clk_get_sys("smp_twd", NULL);
0200
0201     if (IS_ERR(twd_clk)) {
0202         pr_err("smp_twd: clock not found %d\n", (int) PTR_ERR(twd_clk));
0203         return;
0204     }
0205
0206     err = clk_prepare_enable(twd_clk);
0207     if (err) {
0208         pr_err("smp_twd: clock failed to prepare+enable: %d\n", err);
0209         clk_put(twd_clk);
0210         return;
0211     }
0212
0213     twd_timer_rate = clk_get_rate(twd_clk);
0214 }
0215
0216 /*
0217  * Setup the local clock events for a CPU.
0218  */
0219 static void twd_timer_setup(void)
0220 {
0221     struct clock_event_device *clk = raw_cpu_ptr(twd_evt);
0222     int cpu = smp_processor_id();
0223
0224     /*
0225      * If the basic setup for this CPU has been done before don't
0226      * bother with the below.
0227      */
0228     if (per_cpu(percpu_setup_called, cpu)) {
0229         writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
0230         clockevents_register_device(clk);
0231         enable_percpu_irq(clk->irq, 0);
0232         return;
0233     }
0234     per_cpu(percpu_setup_called, cpu) = true;
0235
0236     twd_calibrate_rate();
0237
0238     /*
0239      * The following is done once per CPU the first time .setup() is
0240      * called.
0241      */
0242     writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
0243
0244     clk->name = "local_timer";
0245     clk->features = twd_features;
0246     clk->rating = 350;
0247     clk->set_state_shutdown = twd_shutdown;
0248     clk->set_state_periodic = twd_set_periodic;
0249     clk->set_state_oneshot = twd_set_oneshot;
0250     clk->tick_resume = twd_shutdown;
0251     clk->set_next_event = twd_set_next_event;
0252     clk->irq = twd_ppi;
0253     clk->cpumask = cpumask_of(cpu);
0254
0255     clockevents_config_and_register(clk, twd_timer_rate,
0256                     0xf, 0xffffffff);
0257     enable_percpu_irq(clk->irq, 0);
0258 }
0259
0260 static int twd_timer_starting_cpu(unsigned int cpu)
0261 {
0262     twd_timer_setup();
0263     return 0;
0264 }
0265
0266 static int twd_timer_dying_cpu(unsigned int cpu)
0267 {
0268     twd_timer_stop();
0269     return 0;
0270 }
0271
0272 static int __init twd_local_timer_common_register(struct device_node *np)
0273 {
0274     int err;
0275
0276     twd_evt = alloc_percpu(struct clock_event_device);
0277     if (!twd_evt) {
0278         err = -ENOMEM;
0279         goto out_free;
0280     }
0281
0282     err = request_percpu_irq(twd_ppi, twd_handler, "twd", twd_evt);
0283     if (err) {
0284         pr_err("twd: can't register interrupt %d (%d)\n", twd_ppi, err);
0285         goto out_free;
0286     }
0287
0288     cpuhp_setup_state_nocalls(CPUHP_AP_ARM_TWD_STARTING,
0289                   "arm/timer/twd:starting",
0290                   twd_timer_starting_cpu, twd_timer_dying_cpu);
0291
0292     twd_get_clock(np);
0293     if (!of_property_read_bool(np, "always-on"))
0294         twd_features |= CLOCK_EVT_FEAT_C3STOP;
0295
0296     /*
0297      * Immediately configure the timer on the boot CPU, unless we need
0298      * jiffies to be incrementing to calibrate the rate in which case
0299      * setup the timer in late_time_init.
0300      */
0301     if (twd_timer_rate)
0302         twd_timer_setup();
0303     else
0304         late_time_init = twd_timer_setup;
0305
0306     return 0;
0307
0308 out_free:
0309     iounmap(twd_base);
0310     twd_base = NULL;
0311     free_percpu(twd_evt);
0312
0313     return err;
0314 }
0315
0316 static int __init twd_local_timer_of_register(struct device_node *np)
0317 {
0318     int err;
0319
0320     twd_ppi = irq_of_parse_and_map(np, 0);
0321     if (!twd_ppi) {
0322         err = -EINVAL;
0323         goto out;
0324     }
0325
0326     twd_base = of_iomap(np, 0);
0327     if (!twd_base) {
0328         err = -ENOMEM;
0329         goto out;
0330     }
0331
0332     err = twd_local_timer_common_register(np);
0333
0334 out:
0335     WARN(err, "twd_local_timer_of_register failed (%d)\n", err);
0336     return err;
0337 }
0338 TIMER_OF_DECLARE(arm_twd_a9, "arm,cortex-a9-twd-timer", twd_local_timer_of_register);
0339 TIMER_OF_DECLARE(arm_twd_a5, "arm,cortex-a5-twd-timer", twd_local_timer_of_register);
0340 TIMER_OF_DECLARE(arm_twd_11mp, "arm,arm11mp-twd-timer", twd_local_timer_of_register);