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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 <[email protected]>
7 * Author: Srinivas Kandagatla <[email protected]>
8 */
9
10#include <linux/init.h>
11#include <linux/interrupt.h>
12#include <linux/bitfield.h>
13#include <linux/clocksource.h>
14#include <linux/clockchips.h>
15#include <linux/cpu.h>
16#include <linux/clk.h>
17#include <linux/delay.h>
18#include <linux/err.h>
19#include <linux/io.h>
20#include <linux/of.h>
21#include <linux/of_irq.h>
22#include <linux/of_address.h>
23#include <linux/sched_clock.h>
24
25#include <asm/cputype.h>
26
27#define GT_COUNTER0 0x00
28#define GT_COUNTER1 0x04
29
30#define GT_CONTROL 0x08
31#define GT_CONTROL_TIMER_ENABLE BIT(0) /* this bit is NOT banked */
32#define GT_CONTROL_COMP_ENABLE BIT(1) /* banked */
33#define GT_CONTROL_IRQ_ENABLE BIT(2) /* banked */
34#define GT_CONTROL_AUTO_INC BIT(3) /* banked */
35#define GT_CONTROL_PRESCALER_MASK GENMASK(15, 8)
36
37#define GT_INT_STATUS 0x0c
38#define GT_INT_STATUS_EVENT_FLAG BIT(0)
39
40#define GT_COMP0 0x10
41#define GT_COMP1 0x14
42#define GT_AUTO_INC 0x18
43
44#define MAX_F_ERR 50
45/*
46 * We are expecting to be clocked by the ARM peripheral clock.
47 *
48 * Note: it is assumed we are using a prescaler value of zero, so this is
49 * the units for all operations.
50 */
51static void __iomem *gt_base;
52static struct notifier_block gt_clk_rate_change_nb;
53static u32 gt_psv_new, gt_psv_bck;
54static unsigned long gt_target_rate;
55static int gt_ppi;
56static struct clock_event_device __percpu *gt_evt;
57
58/*
59 * To get the value from the Global Timer Counter register proceed as follows:
60 * 1. Read the upper 32-bit timer counter register
61 * 2. Read the lower 32-bit timer counter register
62 * 3. Read the upper 32-bit timer counter register again. If the value is
63 * different to the 32-bit upper value read previously, go back to step 2.
64 * Otherwise the 64-bit timer counter value is correct.
65 */
66static u64 notrace _gt_counter_read(void)
67{
68 u64 counter;
69 u32 lower;
70 u32 upper, old_upper;
71
72 upper = readl_relaxed(gt_base + GT_COUNTER1);
73 do {
74 old_upper = upper;
75 lower = readl_relaxed(gt_base + GT_COUNTER0);
76 upper = readl_relaxed(gt_base + GT_COUNTER1);
77 } while (upper != old_upper);
78
79 counter = upper;
80 counter <<= 32;
81 counter |= lower;
82 return counter;
83}
84
85static u64 gt_counter_read(void)
86{
87 return _gt_counter_read();
88}
89
90/*
91 * To ensure that updates to comparator value register do not set the
92 * Interrupt Status Register proceed as follows:
93 * 1. Clear the Comp Enable bit in the Timer Control Register.
94 * 2. Write the lower 32-bit Comparator Value Register.
95 * 3. Write the upper 32-bit Comparator Value Register.
96 * 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit.
97 */
98static void gt_compare_set(unsigned long delta, int periodic)
99{
100 u64 counter = gt_counter_read();
101 unsigned long ctrl;
102
103 counter += delta;
104 ctrl = readl(gt_base + GT_CONTROL);
105 ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE |
106 GT_CONTROL_AUTO_INC);
107 ctrl |= GT_CONTROL_TIMER_ENABLE;
108 writel_relaxed(ctrl, gt_base + GT_CONTROL);
109 writel_relaxed(lower_32_bits(counter), gt_base + GT_COMP0);
110 writel_relaxed(upper_32_bits(counter), gt_base + GT_COMP1);
111
112 if (periodic) {
113 writel_relaxed(delta, gt_base + GT_AUTO_INC);
114 ctrl |= GT_CONTROL_AUTO_INC;
115 }
116
117 ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
118 writel_relaxed(ctrl, gt_base + GT_CONTROL);
119}
120
121static int gt_clockevent_shutdown(struct clock_event_device *evt)
122{
123 unsigned long ctrl;
124
125 ctrl = readl(gt_base + GT_CONTROL);
126 ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE |
127 GT_CONTROL_AUTO_INC);
128 writel(ctrl, gt_base + GT_CONTROL);
129 return 0;
130}
131
132static int gt_clockevent_set_periodic(struct clock_event_device *evt)
133{
134 gt_compare_set(DIV_ROUND_CLOSEST(gt_target_rate, HZ), 1);
135 return 0;
136}
137
138static int gt_clockevent_set_next_event(unsigned long evt,
139 struct clock_event_device *unused)
140{
141 gt_compare_set(evt, 0);
142 return 0;
143}
144
145static irqreturn_t gt_clockevent_interrupt(int irq, void *dev_id)
146{
147 struct clock_event_device *evt = dev_id;
148
149 if (!(readl_relaxed(gt_base + GT_INT_STATUS) &
150 GT_INT_STATUS_EVENT_FLAG))
151 return IRQ_NONE;
152
153 /**
154 * ERRATA 740657( Global Timer can send 2 interrupts for
155 * the same event in single-shot mode)
156 * Workaround:
157 * Either disable single-shot mode.
158 * Or
159 * Modify the Interrupt Handler to avoid the
160 * offending sequence. This is achieved by clearing
161 * the Global Timer flag _after_ having incremented
162 * the Comparator register value to a higher value.
163 */
164 if (clockevent_state_oneshot(evt))
165 gt_compare_set(ULONG_MAX, 0);
166
167 writel_relaxed(GT_INT_STATUS_EVENT_FLAG, gt_base + GT_INT_STATUS);
168 evt->event_handler(evt);
169
170 return IRQ_HANDLED;
171}
172
173static int gt_starting_cpu(unsigned int cpu)
174{
175 struct clock_event_device *clk = this_cpu_ptr(gt_evt);
176
177 clk->name = "arm_global_timer";
178 clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
179 CLOCK_EVT_FEAT_PERCPU;
180 clk->set_state_shutdown = gt_clockevent_shutdown;
181 clk->set_state_periodic = gt_clockevent_set_periodic;
182 clk->set_state_oneshot = gt_clockevent_shutdown;
183 clk->set_state_oneshot_stopped = gt_clockevent_shutdown;
184 clk->set_next_event = gt_clockevent_set_next_event;
185 clk->cpumask = cpumask_of(cpu);
186 clk->rating = 300;
187 clk->irq = gt_ppi;
188 clockevents_config_and_register(clk, gt_target_rate,
189 1, 0xffffffff);
190 enable_percpu_irq(clk->irq, IRQ_TYPE_NONE);
191 return 0;
192}
193
194static int gt_dying_cpu(unsigned int cpu)
195{
196 struct clock_event_device *clk = this_cpu_ptr(gt_evt);
197
198 disable_percpu_irq(clk->irq);
199 return 0;
200}
201
202static u64 gt_clocksource_read(struct clocksource *cs)
203{
204 return gt_counter_read();
205}
206
207static void gt_resume(struct clocksource *cs)
208{
209 unsigned long ctrl;
210
211 ctrl = readl(gt_base + GT_CONTROL);
212 if (!(ctrl & GT_CONTROL_TIMER_ENABLE))
213 /* re-enable timer on resume */
214 writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
215}
216
217static struct clocksource gt_clocksource = {
218 .name = "arm_global_timer",
219 .rating = 300,
220 .read = gt_clocksource_read,
221 .mask = CLOCKSOURCE_MASK(64),
222 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
223 .resume = gt_resume,
224};
225
226#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
227static u64 notrace gt_sched_clock_read(void)
228{
229 return _gt_counter_read();
230}
231#endif
232
233static unsigned long gt_read_long(void)
234{
235 return readl_relaxed(gt_base + GT_COUNTER0);
236}
237
238static struct delay_timer gt_delay_timer = {
239 .read_current_timer = gt_read_long,
240};
241
242static void gt_write_presc(u32 psv)
243{
244 u32 reg;
245
246 reg = readl(gt_base + GT_CONTROL);
247 reg &= ~GT_CONTROL_PRESCALER_MASK;
248 reg |= FIELD_PREP(GT_CONTROL_PRESCALER_MASK, psv);
249 writel(reg, gt_base + GT_CONTROL);
250}
251
252static u32 gt_read_presc(void)
253{
254 u32 reg;
255
256 reg = readl(gt_base + GT_CONTROL);
257 return FIELD_GET(GT_CONTROL_PRESCALER_MASK, reg);
258}
259
260static void __init gt_delay_timer_init(void)
261{
262 gt_delay_timer.freq = gt_target_rate;
263 register_current_timer_delay(&gt_delay_timer);
264}
265
266static int __init gt_clocksource_init(unsigned int psv)
267{
268 writel(0, gt_base + GT_CONTROL);
269 writel(0, gt_base + GT_COUNTER0);
270 writel(0, gt_base + GT_COUNTER1);
271 /* set prescaler and enable timer on all the cores */
272 writel(FIELD_PREP(GT_CONTROL_PRESCALER_MASK, psv - 1) |
273 GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
274
275#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
276 sched_clock_register(gt_sched_clock_read, 64, gt_target_rate);
277#endif
278 return clocksource_register_hz(&gt_clocksource, gt_target_rate);
279}
280
281static int gt_clk_rate_change_cb(struct notifier_block *nb,
282 unsigned long event, void *data)
283{
284 struct clk_notifier_data *ndata = data;
285
286 switch (event) {
287 case PRE_RATE_CHANGE:
288 {
289 unsigned long psv;
290
291 psv = DIV_ROUND_CLOSEST(ndata->new_rate, gt_target_rate);
292 if (!psv ||
293 abs(gt_target_rate - (ndata->new_rate / psv)) > MAX_F_ERR)
294 return NOTIFY_BAD;
295
296 psv--;
297
298 /* prescaler within legal range? */
299 if (!FIELD_FIT(GT_CONTROL_PRESCALER_MASK, psv))
300 return NOTIFY_BAD;
301
302 /*
303 * store timer clock ctrl register so we can restore it in case
304 * of an abort.
305 */
306 gt_psv_bck = gt_read_presc();
307 gt_psv_new = psv;
308 /* scale down: adjust divider in post-change notification */
309 if (ndata->new_rate < ndata->old_rate)
310 return NOTIFY_DONE;
311
312 /* scale up: adjust divider now - before frequency change */
313 gt_write_presc(psv);
314 break;
315 }
316 case POST_RATE_CHANGE:
317 /* scale up: pre-change notification did the adjustment */
318 if (ndata->new_rate > ndata->old_rate)
319 return NOTIFY_OK;
320
321 /* scale down: adjust divider now - after frequency change */
322 gt_write_presc(gt_psv_new);
323 break;
324
325 case ABORT_RATE_CHANGE:
326 /* we have to undo the adjustment in case we scale up */
327 if (ndata->new_rate < ndata->old_rate)
328 return NOTIFY_OK;
329
330 /* restore original register value */
331 gt_write_presc(gt_psv_bck);
332 break;
333 default:
334 return NOTIFY_DONE;
335 }
336
337 return NOTIFY_DONE;
338}
339
340struct gt_prescaler_config {
341 const char *compatible;
342 unsigned long prescaler;
343};
344
345static const struct gt_prescaler_config gt_prescaler_configs[] = {
346 /*
347 * On am43 the global timer clock is a child of the clock used for CPU
348 * OPPs, so the initial prescaler has to be compatible with all OPPs
349 * which are 300, 600, 720, 800 and 1000 with a fixed divider of 2, this
350 * gives us a GCD of 10. Initial frequency is 1000, so the prescaler is
351 * 50.
352 */
353 { .compatible = "ti,am43", .prescaler = 50 },
354 { .compatible = "xlnx,zynq-7000", .prescaler = 2 },
355 { .compatible = NULL }
356};
357
358static unsigned long gt_get_initial_prescaler_value(struct device_node *np)
359{
360 const struct gt_prescaler_config *config;
361
362 if (CONFIG_ARM_GT_INITIAL_PRESCALER_VAL != 0)
363 return CONFIG_ARM_GT_INITIAL_PRESCALER_VAL;
364
365 for (config = gt_prescaler_configs; config->compatible; config++) {
366 if (of_machine_is_compatible(config->compatible))
367 return config->prescaler;
368 }
369
370 return 1;
371}
372
373static int __init global_timer_of_register(struct device_node *np)
374{
375 struct clk *gt_clk;
376 static unsigned long gt_clk_rate;
377 int err;
378 unsigned long psv;
379
380 /*
381 * In A9 r2p0 the comparators for each processor with the global timer
382 * fire when the timer value is greater than or equal to. In previous
383 * revisions the comparators fired when the timer value was equal to.
384 */
385 if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9
386 && (read_cpuid_id() & 0xf0000f) < 0x200000) {
387 pr_warn("global-timer: non support for this cpu version.\n");
388 return -ENOSYS;
389 }
390
391 gt_ppi = irq_of_parse_and_map(np, 0);
392 if (!gt_ppi) {
393 pr_warn("global-timer: unable to parse irq\n");
394 return -EINVAL;
395 }
396
397 gt_base = of_iomap(np, 0);
398 if (!gt_base) {
399 pr_warn("global-timer: invalid base address\n");
400 return -ENXIO;
401 }
402
403 gt_clk = of_clk_get(np, 0);
404 if (!IS_ERR(gt_clk)) {
405 err = clk_prepare_enable(gt_clk);
406 if (err)
407 goto out_unmap;
408 } else {
409 pr_warn("global-timer: clk not found\n");
410 err = -EINVAL;
411 goto out_unmap;
412 }
413
414 psv = gt_get_initial_prescaler_value(np);
415 gt_clk_rate = clk_get_rate(gt_clk);
416 gt_target_rate = gt_clk_rate / psv;
417 gt_clk_rate_change_nb.notifier_call =
418 gt_clk_rate_change_cb;
419 err = clk_notifier_register(gt_clk, &gt_clk_rate_change_nb);
420 if (err) {
421 pr_warn("Unable to register clock notifier\n");
422 goto out_clk;
423 }
424
425 gt_evt = alloc_percpu(struct clock_event_device);
426 if (!gt_evt) {
427 pr_warn("global-timer: can't allocate memory\n");
428 err = -ENOMEM;
429 goto out_clk_nb;
430 }
431
432 err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt,
433 "gt", gt_evt);
434 if (err) {
435 pr_warn("global-timer: can't register interrupt %d (%d)\n",
436 gt_ppi, err);
437 goto out_free;
438 }
439
440 /* Register and immediately configure the timer on the boot CPU */
441 err = gt_clocksource_init(psv);
442 if (err)
443 goto out_irq;
444
445 err = cpuhp_setup_state(CPUHP_AP_ARM_GLOBAL_TIMER_STARTING,
446 "clockevents/arm/global_timer:starting",
447 gt_starting_cpu, gt_dying_cpu);
448 if (err)
449 goto out_irq;
450
451 gt_delay_timer_init();
452
453 return 0;
454
455out_irq:
456 free_percpu_irq(gt_ppi, gt_evt);
457out_free:
458 free_percpu(gt_evt);
459out_clk_nb:
460 clk_notifier_unregister(gt_clk, &gt_clk_rate_change_nb);
461out_clk:
462 clk_disable_unprepare(gt_clk);
463out_unmap:
464 iounmap(gt_base);
465 WARN(err, "ARM Global timer register failed (%d)\n", err);
466
467 return err;
468}
469
470/* Only tested on r2p2 and r3p0 */
471TIMER_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
472 global_timer_of_register);