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 */
 26static void __iomem *twd_base;
 27
 28static struct clk *twd_clk;
 29static unsigned long twd_timer_rate;
 30static DEFINE_PER_CPU(bool, percpu_setup_called);
 31
 32static struct clock_event_device __percpu *twd_evt;
 33static unsigned int twd_features =
 34		CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
 35static int twd_ppi;
 36
 37static int twd_shutdown(struct clock_event_device *clk)
 38{
 39	writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
 40	return 0;
 41}
 42
 43static 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
 51static 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
 63static 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 */
 82static 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
 92static 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 */
103static 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
110static 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
127static struct notifier_block twd_clk_nb = {
128	.notifier_call = twd_rate_change,
129};
130
131static 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}
138core_initcall(twd_clk_init);
139
140static 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
179static 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
191static 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 */
218static 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
259static int twd_timer_starting_cpu(unsigned int cpu)
260{
261	twd_timer_setup();
262	return 0;
263}
264
265static int twd_timer_dying_cpu(unsigned int cpu)
266{
267	twd_timer_stop();
268	return 0;
269}
270
271static 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
307out_free:
308	iounmap(twd_base);
309	twd_base = NULL;
310	free_percpu(twd_evt);
311
312	return err;
313}
314
315static 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
333out:
334	WARN(err, "twd_local_timer_of_register failed (%d)\n", err);
335	return err;
336}
337TIMER_OF_DECLARE(arm_twd_a9, "arm,cortex-a9-twd-timer", twd_local_timer_of_register);
338TIMER_OF_DECLARE(arm_twd_a5, "arm,cortex-a5-twd-timer", twd_local_timer_of_register);
339TIMER_OF_DECLARE(arm_twd_11mp, "arm,arm11mp-twd-timer", twd_local_timer_of_register);