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/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(addr: 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(addr: gt_base + GT_CONTROL);
126 ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE |
127 GT_CONTROL_AUTO_INC);
128 writel(val: ctrl, addr: 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), periodic: 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(delta: evt, periodic: 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(dev: evt))
165 gt_compare_set(ULONG_MAX, periodic: 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(dev: clk, freq: gt_target_rate,
189 min_delta: 1, max_delta: 0xffffffff);
190 enable_percpu_irq(irq: clk->irq, type: 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 gt_clockevent_shutdown(evt: clk);
199 disable_percpu_irq(irq: clk->irq);
200 return 0;
201}
202
203static u64 gt_clocksource_read(struct clocksource *cs)
204{
205 return gt_counter_read();
206}
207
208static void gt_resume(struct clocksource *cs)
209{
210 unsigned long ctrl;
211
212 ctrl = readl(addr: gt_base + GT_CONTROL);
213 if (!(ctrl & GT_CONTROL_TIMER_ENABLE))
214 /* re-enable timer on resume */
215 writel(GT_CONTROL_TIMER_ENABLE, addr: gt_base + GT_CONTROL);
216}
217
218static struct clocksource gt_clocksource = {
219 .name = "arm_global_timer",
220 .rating = 300,
221 .read = gt_clocksource_read,
222 .mask = CLOCKSOURCE_MASK(64),
223 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
224 .resume = gt_resume,
225};
226
227#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
228static u64 notrace gt_sched_clock_read(void)
229{
230 return _gt_counter_read();
231}
232#endif
233
234static unsigned long gt_read_long(void)
235{
236 return readl_relaxed(gt_base + GT_COUNTER0);
237}
238
239static struct delay_timer gt_delay_timer = {
240 .read_current_timer = gt_read_long,
241};
242
243static void gt_write_presc(u32 psv)
244{
245 u32 reg;
246
247 reg = readl(addr: gt_base + GT_CONTROL);
248 reg &= ~GT_CONTROL_PRESCALER_MASK;
249 reg |= FIELD_PREP(GT_CONTROL_PRESCALER_MASK, psv);
250 writel(val: reg, addr: gt_base + GT_CONTROL);
251}
252
253static u32 gt_read_presc(void)
254{
255 u32 reg;
256
257 reg = readl(addr: gt_base + GT_CONTROL);
258 return FIELD_GET(GT_CONTROL_PRESCALER_MASK, reg);
259}
260
261static void __init gt_delay_timer_init(void)
262{
263 gt_delay_timer.freq = gt_target_rate;
264 register_current_timer_delay(&gt_delay_timer);
265}
266
267static int __init gt_clocksource_init(void)
268{
269 writel(val: 0, addr: gt_base + GT_CONTROL);
270 writel(val: 0, addr: gt_base + GT_COUNTER0);
271 writel(val: 0, addr: gt_base + GT_COUNTER1);
272 /* set prescaler and enable timer on all the cores */
273 writel(FIELD_PREP(GT_CONTROL_PRESCALER_MASK,
274 CONFIG_ARM_GT_INITIAL_PRESCALER_VAL - 1) |
275 GT_CONTROL_TIMER_ENABLE, addr: gt_base + GT_CONTROL);
276
277#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
278 sched_clock_register(gt_sched_clock_read, 64, gt_target_rate);
279#endif
280 return clocksource_register_hz(cs: &gt_clocksource, hz: gt_target_rate);
281}
282
283static int gt_clk_rate_change_cb(struct notifier_block *nb,
284 unsigned long event, void *data)
285{
286 struct clk_notifier_data *ndata = data;
287
288 switch (event) {
289 case PRE_RATE_CHANGE:
290 {
291 unsigned long psv;
292
293 psv = DIV_ROUND_CLOSEST(ndata->new_rate, gt_target_rate);
294 if (!psv ||
295 abs(gt_target_rate - (ndata->new_rate / psv)) > MAX_F_ERR)
296 return NOTIFY_BAD;
297
298 psv--;
299
300 /* prescaler within legal range? */
301 if (!FIELD_FIT(GT_CONTROL_PRESCALER_MASK, psv))
302 return NOTIFY_BAD;
303
304 /*
305 * store timer clock ctrl register so we can restore it in case
306 * of an abort.
307 */
308 gt_psv_bck = gt_read_presc();
309 gt_psv_new = psv;
310 /* scale down: adjust divider in post-change notification */
311 if (ndata->new_rate < ndata->old_rate)
312 return NOTIFY_DONE;
313
314 /* scale up: adjust divider now - before frequency change */
315 gt_write_presc(psv);
316 break;
317 }
318 case POST_RATE_CHANGE:
319 /* scale up: pre-change notification did the adjustment */
320 if (ndata->new_rate > ndata->old_rate)
321 return NOTIFY_OK;
322
323 /* scale down: adjust divider now - after frequency change */
324 gt_write_presc(psv: gt_psv_new);
325 break;
326
327 case ABORT_RATE_CHANGE:
328 /* we have to undo the adjustment in case we scale up */
329 if (ndata->new_rate < ndata->old_rate)
330 return NOTIFY_OK;
331
332 /* restore original register value */
333 gt_write_presc(psv: gt_psv_bck);
334 break;
335 default:
336 return NOTIFY_DONE;
337 }
338
339 return NOTIFY_DONE;
340}
341
342static int __init global_timer_of_register(struct device_node *np)
343{
344 struct clk *gt_clk;
345 static unsigned long gt_clk_rate;
346 int err = 0;
347
348 /*
349 * In A9 r2p0 the comparators for each processor with the global timer
350 * fire when the timer value is greater than or equal to. In previous
351 * revisions the comparators fired when the timer value was equal to.
352 */
353 if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9
354 && (read_cpuid_id() & 0xf0000f) < 0x200000) {
355 pr_warn("global-timer: non support for this cpu version.\n");
356 return -ENOSYS;
357 }
358
359 gt_ppi = irq_of_parse_and_map(node: np, index: 0);
360 if (!gt_ppi) {
361 pr_warn("global-timer: unable to parse irq\n");
362 return -EINVAL;
363 }
364
365 gt_base = of_iomap(node: np, index: 0);
366 if (!gt_base) {
367 pr_warn("global-timer: invalid base address\n");
368 return -ENXIO;
369 }
370
371 gt_clk = of_clk_get(np, index: 0);
372 if (!IS_ERR(ptr: gt_clk)) {
373 err = clk_prepare_enable(clk: gt_clk);
374 if (err)
375 goto out_unmap;
376 } else {
377 pr_warn("global-timer: clk not found\n");
378 err = -EINVAL;
379 goto out_unmap;
380 }
381
382 gt_clk_rate = clk_get_rate(clk: gt_clk);
383 gt_target_rate = gt_clk_rate / CONFIG_ARM_GT_INITIAL_PRESCALER_VAL;
384 gt_clk_rate_change_nb.notifier_call =
385 gt_clk_rate_change_cb;
386 err = clk_notifier_register(clk: gt_clk, nb: &gt_clk_rate_change_nb);
387 if (err) {
388 pr_warn("Unable to register clock notifier\n");
389 goto out_clk;
390 }
391
392 gt_evt = alloc_percpu(struct clock_event_device);
393 if (!gt_evt) {
394 pr_warn("global-timer: can't allocate memory\n");
395 err = -ENOMEM;
396 goto out_clk_nb;
397 }
398
399 err = request_percpu_irq(irq: gt_ppi, handler: gt_clockevent_interrupt,
400 devname: "gt", percpu_dev_id: gt_evt);
401 if (err) {
402 pr_warn("global-timer: can't register interrupt %d (%d)\n",
403 gt_ppi, err);
404 goto out_free;
405 }
406
407 /* Register and immediately configure the timer on the boot CPU */
408 err = gt_clocksource_init();
409 if (err)
410 goto out_irq;
411
412 err = cpuhp_setup_state(state: CPUHP_AP_ARM_GLOBAL_TIMER_STARTING,
413 name: "clockevents/arm/global_timer:starting",
414 startup: gt_starting_cpu, teardown: gt_dying_cpu);
415 if (err)
416 goto out_irq;
417
418 gt_delay_timer_init();
419
420 return 0;
421
422out_irq:
423 free_percpu_irq(gt_ppi, gt_evt);
424out_free:
425 free_percpu(pdata: gt_evt);
426out_clk_nb:
427 clk_notifier_unregister(clk: gt_clk, nb: &gt_clk_rate_change_nb);
428out_clk:
429 clk_disable_unprepare(clk: gt_clk);
430out_unmap:
431 iounmap(addr: gt_base);
432 WARN(err, "ARM Global timer register failed (%d)\n", err);
433
434 return err;
435}
436
437/* Only tested on r2p2 and r3p0 */
438TIMER_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
439 global_timer_of_register);
440

source code of linux/drivers/clocksource/arm_global_timer.c