1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * drivers/clocksource/arm_global_timer.c
4  *
5  * Copyright (C) 2013 STMicroelectronics (R&D) Limited.
6  * Author: Stuart Menefy <stuart.menefy@st.com>
7  * Author: Srinivas Kandagatla <srinivas.kandagatla@st.com>
8  */
9 
10 #include <linux/init.h>
11 #include <linux/interrupt.h>
12 #include <linux/clocksource.h>
13 #include <linux/clockchips.h>
14 #include <linux/cpu.h>
15 #include <linux/clk.h>
16 #include <linux/delay.h>
17 #include <linux/err.h>
18 #include <linux/io.h>
19 #include <linux/of.h>
20 #include <linux/of_irq.h>
21 #include <linux/of_address.h>
22 #include <linux/sched_clock.h>
23 
24 #include <asm/cputype.h>
25 
26 #define GT_COUNTER0	0x00
27 #define GT_COUNTER1	0x04
28 
29 #define GT_CONTROL	0x08
30 #define GT_CONTROL_TIMER_ENABLE		BIT(0)  /* this bit is NOT banked */
31 #define GT_CONTROL_COMP_ENABLE		BIT(1)	/* banked */
32 #define GT_CONTROL_IRQ_ENABLE		BIT(2)	/* banked */
33 #define GT_CONTROL_AUTO_INC		BIT(3)	/* banked */
34 #define GT_CONTROL_PRESCALER_SHIFT      8
35 #define GT_CONTROL_PRESCALER_MAX        0xFF
36 #define GT_CONTROL_PRESCALER_MASK       (GT_CONTROL_PRESCALER_MAX << \
37 					 GT_CONTROL_PRESCALER_SHIFT)
38 
39 #define GT_INT_STATUS	0x0c
40 #define GT_INT_STATUS_EVENT_FLAG	BIT(0)
41 
42 #define GT_COMP0	0x10
43 #define GT_COMP1	0x14
44 #define GT_AUTO_INC	0x18
45 
46 #define MAX_F_ERR 50
47 /*
48  * We are expecting to be clocked by the ARM peripheral clock.
49  *
50  * Note: it is assumed we are using a prescaler value of zero, so this is
51  * the units for all operations.
52  */
53 static void __iomem *gt_base;
54 static struct notifier_block gt_clk_rate_change_nb;
55 static u32 gt_psv_new, gt_psv_bck, gt_target_rate;
56 static int gt_ppi;
57 static struct clock_event_device __percpu *gt_evt;
58 
59 /*
60  * To get the value from the Global Timer Counter register proceed as follows:
61  * 1. Read the upper 32-bit timer counter register
62  * 2. Read the lower 32-bit timer counter register
63  * 3. Read the upper 32-bit timer counter register again. If the value is
64  *  different to the 32-bit upper value read previously, go back to step 2.
65  *  Otherwise the 64-bit timer counter value is correct.
66  */
_gt_counter_read(void)67 static u64 notrace _gt_counter_read(void)
68 {
69 	u64 counter;
70 	u32 lower;
71 	u32 upper, old_upper;
72 
73 	upper = readl_relaxed(gt_base + GT_COUNTER1);
74 	do {
75 		old_upper = upper;
76 		lower = readl_relaxed(gt_base + GT_COUNTER0);
77 		upper = readl_relaxed(gt_base + GT_COUNTER1);
78 	} while (upper != old_upper);
79 
80 	counter = upper;
81 	counter <<= 32;
82 	counter |= lower;
83 	return counter;
84 }
85 
gt_counter_read(void)86 static u64 gt_counter_read(void)
87 {
88 	return _gt_counter_read();
89 }
90 
91 /**
92  * To ensure that updates to comparator value register do not set the
93  * Interrupt Status Register proceed as follows:
94  * 1. Clear the Comp Enable bit in the Timer Control Register.
95  * 2. Write the lower 32-bit Comparator Value Register.
96  * 3. Write the upper 32-bit Comparator Value Register.
97  * 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit.
98  */
gt_compare_set(unsigned long delta,int periodic)99 static void gt_compare_set(unsigned long delta, int periodic)
100 {
101 	u64 counter = gt_counter_read();
102 	unsigned long ctrl;
103 
104 	counter += delta;
105 	ctrl = readl(gt_base + GT_CONTROL);
106 	ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE |
107 		  GT_CONTROL_AUTO_INC);
108 	ctrl |= GT_CONTROL_TIMER_ENABLE;
109 	writel_relaxed(ctrl, gt_base + GT_CONTROL);
110 	writel_relaxed(lower_32_bits(counter), gt_base + GT_COMP0);
111 	writel_relaxed(upper_32_bits(counter), gt_base + GT_COMP1);
112 
113 	if (periodic) {
114 		writel_relaxed(delta, gt_base + GT_AUTO_INC);
115 		ctrl |= GT_CONTROL_AUTO_INC;
116 	}
117 
118 	ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
119 	writel_relaxed(ctrl, gt_base + GT_CONTROL);
120 }
121 
gt_clockevent_shutdown(struct clock_event_device * evt)122 static int gt_clockevent_shutdown(struct clock_event_device *evt)
123 {
124 	unsigned long ctrl;
125 
126 	ctrl = readl(gt_base + GT_CONTROL);
127 	ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE |
128 		  GT_CONTROL_AUTO_INC);
129 	writel(ctrl, gt_base + GT_CONTROL);
130 	return 0;
131 }
132 
gt_clockevent_set_periodic(struct clock_event_device * evt)133 static int gt_clockevent_set_periodic(struct clock_event_device *evt)
134 {
135 	gt_compare_set(DIV_ROUND_CLOSEST(gt_target_rate, HZ), 1);
136 	return 0;
137 }
138 
gt_clockevent_set_next_event(unsigned long evt,struct clock_event_device * unused)139 static int gt_clockevent_set_next_event(unsigned long evt,
140 					struct clock_event_device *unused)
141 {
142 	gt_compare_set(evt, 0);
143 	return 0;
144 }
145 
gt_clockevent_interrupt(int irq,void * dev_id)146 static irqreturn_t gt_clockevent_interrupt(int irq, void *dev_id)
147 {
148 	struct clock_event_device *evt = dev_id;
149 
150 	if (!(readl_relaxed(gt_base + GT_INT_STATUS) &
151 				GT_INT_STATUS_EVENT_FLAG))
152 		return IRQ_NONE;
153 
154 	/**
155 	 * ERRATA 740657( Global Timer can send 2 interrupts for
156 	 * the same event in single-shot mode)
157 	 * Workaround:
158 	 *	Either disable single-shot mode.
159 	 *	Or
160 	 *	Modify the Interrupt Handler to avoid the
161 	 *	offending sequence. This is achieved by clearing
162 	 *	the Global Timer flag _after_ having incremented
163 	 *	the Comparator register	value to a higher value.
164 	 */
165 	if (clockevent_state_oneshot(evt))
166 		gt_compare_set(ULONG_MAX, 0);
167 
168 	writel_relaxed(GT_INT_STATUS_EVENT_FLAG, gt_base + GT_INT_STATUS);
169 	evt->event_handler(evt);
170 
171 	return IRQ_HANDLED;
172 }
173 
gt_starting_cpu(unsigned int cpu)174 static int gt_starting_cpu(unsigned int cpu)
175 {
176 	struct clock_event_device *clk = this_cpu_ptr(gt_evt);
177 
178 	clk->name = "arm_global_timer";
179 	clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
180 		CLOCK_EVT_FEAT_PERCPU;
181 	clk->set_state_shutdown = gt_clockevent_shutdown;
182 	clk->set_state_periodic = gt_clockevent_set_periodic;
183 	clk->set_state_oneshot = gt_clockevent_shutdown;
184 	clk->set_state_oneshot_stopped = gt_clockevent_shutdown;
185 	clk->set_next_event = gt_clockevent_set_next_event;
186 	clk->cpumask = cpumask_of(cpu);
187 	clk->rating = 300;
188 	clk->irq = gt_ppi;
189 	clockevents_config_and_register(clk, gt_target_rate,
190 					1, 0xffffffff);
191 	enable_percpu_irq(clk->irq, IRQ_TYPE_NONE);
192 	return 0;
193 }
194 
gt_dying_cpu(unsigned int cpu)195 static int gt_dying_cpu(unsigned int cpu)
196 {
197 	struct clock_event_device *clk = this_cpu_ptr(gt_evt);
198 
199 	gt_clockevent_shutdown(clk);
200 	disable_percpu_irq(clk->irq);
201 	return 0;
202 }
203 
gt_clocksource_read(struct clocksource * cs)204 static u64 gt_clocksource_read(struct clocksource *cs)
205 {
206 	return gt_counter_read();
207 }
208 
gt_resume(struct clocksource * cs)209 static void gt_resume(struct clocksource *cs)
210 {
211 	unsigned long ctrl;
212 
213 	ctrl = readl(gt_base + GT_CONTROL);
214 	if (!(ctrl & GT_CONTROL_TIMER_ENABLE))
215 		/* re-enable timer on resume */
216 		writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
217 }
218 
219 static struct clocksource gt_clocksource = {
220 	.name	= "arm_global_timer",
221 	.rating	= 300,
222 	.read	= gt_clocksource_read,
223 	.mask	= CLOCKSOURCE_MASK(64),
224 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
225 	.resume = gt_resume,
226 };
227 
228 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
gt_sched_clock_read(void)229 static u64 notrace gt_sched_clock_read(void)
230 {
231 	return _gt_counter_read();
232 }
233 #endif
234 
gt_read_long(void)235 static unsigned long gt_read_long(void)
236 {
237 	return readl_relaxed(gt_base + GT_COUNTER0);
238 }
239 
240 static struct delay_timer gt_delay_timer = {
241 	.read_current_timer = gt_read_long,
242 };
243 
gt_write_presc(u32 psv)244 static void gt_write_presc(u32 psv)
245 {
246 	u32 reg;
247 
248 	reg = readl(gt_base + GT_CONTROL);
249 	reg &= ~GT_CONTROL_PRESCALER_MASK;
250 	reg |= psv << GT_CONTROL_PRESCALER_SHIFT;
251 	writel(reg, gt_base + GT_CONTROL);
252 }
253 
gt_read_presc(void)254 static u32 gt_read_presc(void)
255 {
256 	u32 reg;
257 
258 	reg = readl(gt_base + GT_CONTROL);
259 	reg &= GT_CONTROL_PRESCALER_MASK;
260 	return reg >> GT_CONTROL_PRESCALER_SHIFT;
261 }
262 
gt_delay_timer_init(void)263 static void __init gt_delay_timer_init(void)
264 {
265 	gt_delay_timer.freq = gt_target_rate;
266 	register_current_timer_delay(&gt_delay_timer);
267 }
268 
gt_clocksource_init(void)269 static int __init gt_clocksource_init(void)
270 {
271 	writel(0, gt_base + GT_CONTROL);
272 	writel(0, gt_base + GT_COUNTER0);
273 	writel(0, gt_base + GT_COUNTER1);
274 	/* set prescaler and enable timer on all the cores */
275 	writel(((CONFIG_ARM_GT_INITIAL_PRESCALER_VAL - 1) <<
276 		GT_CONTROL_PRESCALER_SHIFT)
277 	       | GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
278 
279 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
280 	sched_clock_register(gt_sched_clock_read, 64, gt_target_rate);
281 #endif
282 	return clocksource_register_hz(&gt_clocksource, gt_target_rate);
283 }
284 
gt_clk_rate_change_cb(struct notifier_block * nb,unsigned long event,void * data)285 static int gt_clk_rate_change_cb(struct notifier_block *nb,
286 				 unsigned long event, void *data)
287 {
288 	struct clk_notifier_data *ndata = data;
289 
290 	switch (event) {
291 	case PRE_RATE_CHANGE:
292 	{
293 		unsigned long psv;
294 
295 		psv = DIV_ROUND_CLOSEST(ndata->new_rate, gt_target_rate);
296 		if (!psv ||
297 		    abs(gt_target_rate - (ndata->new_rate / psv)) > MAX_F_ERR)
298 			return NOTIFY_BAD;
299 
300 		psv--;
301 
302 		/* prescaler within legal range? */
303 		if (psv > GT_CONTROL_PRESCALER_MAX)
304 			return NOTIFY_BAD;
305 
306 		/*
307 		 * store timer clock ctrl register so we can restore it in case
308 		 * of an abort.
309 		 */
310 		gt_psv_bck = gt_read_presc();
311 		gt_psv_new = psv;
312 		/* scale down: adjust divider in post-change notification */
313 		if (ndata->new_rate < ndata->old_rate)
314 			return NOTIFY_DONE;
315 
316 		/* scale up: adjust divider now - before frequency change */
317 		gt_write_presc(psv);
318 		break;
319 	}
320 	case POST_RATE_CHANGE:
321 		/* scale up: pre-change notification did the adjustment */
322 		if (ndata->new_rate > ndata->old_rate)
323 			return NOTIFY_OK;
324 
325 		/* scale down: adjust divider now - after frequency change */
326 		gt_write_presc(gt_psv_new);
327 		break;
328 
329 	case ABORT_RATE_CHANGE:
330 		/* we have to undo the adjustment in case we scale up */
331 		if (ndata->new_rate < ndata->old_rate)
332 			return NOTIFY_OK;
333 
334 		/* restore original register value */
335 		gt_write_presc(gt_psv_bck);
336 		break;
337 	default:
338 		return NOTIFY_DONE;
339 	}
340 
341 	return NOTIFY_DONE;
342 }
343 
global_timer_of_register(struct device_node * np)344 static int __init global_timer_of_register(struct device_node *np)
345 {
346 	struct clk *gt_clk;
347 	static unsigned long gt_clk_rate;
348 	int err = 0;
349 
350 	/*
351 	 * In A9 r2p0 the comparators for each processor with the global timer
352 	 * fire when the timer value is greater than or equal to. In previous
353 	 * revisions the comparators fired when the timer value was equal to.
354 	 */
355 	if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9
356 	    && (read_cpuid_id() & 0xf0000f) < 0x200000) {
357 		pr_warn("global-timer: non support for this cpu version.\n");
358 		return -ENOSYS;
359 	}
360 
361 	gt_ppi = irq_of_parse_and_map(np, 0);
362 	if (!gt_ppi) {
363 		pr_warn("global-timer: unable to parse irq\n");
364 		return -EINVAL;
365 	}
366 
367 	gt_base = of_iomap(np, 0);
368 	if (!gt_base) {
369 		pr_warn("global-timer: invalid base address\n");
370 		return -ENXIO;
371 	}
372 
373 	gt_clk = of_clk_get(np, 0);
374 	if (!IS_ERR(gt_clk)) {
375 		err = clk_prepare_enable(gt_clk);
376 		if (err)
377 			goto out_unmap;
378 	} else {
379 		pr_warn("global-timer: clk not found\n");
380 		err = -EINVAL;
381 		goto out_unmap;
382 	}
383 
384 	gt_clk_rate = clk_get_rate(gt_clk);
385 	gt_target_rate = gt_clk_rate / CONFIG_ARM_GT_INITIAL_PRESCALER_VAL;
386 	gt_clk_rate_change_nb.notifier_call =
387 		gt_clk_rate_change_cb;
388 	err = clk_notifier_register(gt_clk, &gt_clk_rate_change_nb);
389 	if (err) {
390 		pr_warn("Unable to register clock notifier\n");
391 		goto out_clk;
392 	}
393 
394 	gt_evt = alloc_percpu(struct clock_event_device);
395 	if (!gt_evt) {
396 		pr_warn("global-timer: can't allocate memory\n");
397 		err = -ENOMEM;
398 		goto out_clk_nb;
399 	}
400 
401 	err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt,
402 				 "gt", gt_evt);
403 	if (err) {
404 		pr_warn("global-timer: can't register interrupt %d (%d)\n",
405 			gt_ppi, err);
406 		goto out_free;
407 	}
408 
409 	/* Register and immediately configure the timer on the boot CPU */
410 	err = gt_clocksource_init();
411 	if (err)
412 		goto out_irq;
413 
414 	err = cpuhp_setup_state(CPUHP_AP_ARM_GLOBAL_TIMER_STARTING,
415 				"clockevents/arm/global_timer:starting",
416 				gt_starting_cpu, gt_dying_cpu);
417 	if (err)
418 		goto out_irq;
419 
420 	gt_delay_timer_init();
421 
422 	return 0;
423 
424 out_irq:
425 	free_percpu_irq(gt_ppi, gt_evt);
426 out_free:
427 	free_percpu(gt_evt);
428 out_clk_nb:
429 	clk_notifier_unregister(gt_clk, &gt_clk_rate_change_nb);
430 out_clk:
431 	clk_disable_unprepare(gt_clk);
432 out_unmap:
433 	iounmap(gt_base);
434 	WARN(err, "ARM Global timer register failed (%d)\n", err);
435 
436 	return err;
437 }
438 
439 /* Only tested on r2p2 and r3p0  */
440 TIMER_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
441 			global_timer_of_register);
442