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 */
51 static void __iomem *gt_base;
52 static struct notifier_block gt_clk_rate_change_nb;
53 static u32 gt_psv_new, gt_psv_bck;
54 static unsigned long gt_target_rate;
55 static int gt_ppi;
56 static 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 */
_gt_counter_read(void)66 static 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
gt_counter_read(void)85 static 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 */
gt_compare_set(unsigned long delta,int periodic)98 static 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
gt_clockevent_shutdown(struct clock_event_device * evt)121 static 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
gt_clockevent_set_periodic(struct clock_event_device * evt)132 static 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
gt_clockevent_set_next_event(unsigned long evt,struct clock_event_device * unused)138 static 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
gt_clockevent_interrupt(int irq,void * dev_id)145 static 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
gt_starting_cpu(unsigned int cpu)173 static 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
gt_dying_cpu(unsigned int cpu)194 static int gt_dying_cpu(unsigned int cpu)
195 {
196 struct clock_event_device *clk = this_cpu_ptr(gt_evt);
197
198 gt_clockevent_shutdown(clk);
199 disable_percpu_irq(clk->irq);
200 return 0;
201 }
202
gt_clocksource_read(struct clocksource * cs)203 static u64 gt_clocksource_read(struct clocksource *cs)
204 {
205 return gt_counter_read();
206 }
207
gt_resume(struct clocksource * cs)208 static void gt_resume(struct clocksource *cs)
209 {
210 unsigned long ctrl;
211
212 ctrl = readl(gt_base + GT_CONTROL);
213 if (!(ctrl & GT_CONTROL_TIMER_ENABLE))
214 /* re-enable timer on resume */
215 writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
216 }
217
218 static 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
gt_sched_clock_read(void)228 static u64 notrace gt_sched_clock_read(void)
229 {
230 return _gt_counter_read();
231 }
232 #endif
233
gt_read_long(void)234 static unsigned long gt_read_long(void)
235 {
236 return readl_relaxed(gt_base + GT_COUNTER0);
237 }
238
239 static struct delay_timer gt_delay_timer = {
240 .read_current_timer = gt_read_long,
241 };
242
gt_write_presc(u32 psv)243 static void gt_write_presc(u32 psv)
244 {
245 u32 reg;
246
247 reg = readl(gt_base + GT_CONTROL);
248 reg &= ~GT_CONTROL_PRESCALER_MASK;
249 reg |= FIELD_PREP(GT_CONTROL_PRESCALER_MASK, psv);
250 writel(reg, gt_base + GT_CONTROL);
251 }
252
gt_read_presc(void)253 static u32 gt_read_presc(void)
254 {
255 u32 reg;
256
257 reg = readl(gt_base + GT_CONTROL);
258 return FIELD_GET(GT_CONTROL_PRESCALER_MASK, reg);
259 }
260
gt_delay_timer_init(void)261 static void __init gt_delay_timer_init(void)
262 {
263 gt_delay_timer.freq = gt_target_rate;
264 register_current_timer_delay(>_delay_timer);
265 }
266
gt_clocksource_init(void)267 static int __init gt_clocksource_init(void)
268 {
269 writel(0, gt_base + GT_CONTROL);
270 writel(0, gt_base + GT_COUNTER0);
271 writel(0, 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, 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(>_clocksource, gt_target_rate);
281 }
282
gt_clk_rate_change_cb(struct notifier_block * nb,unsigned long event,void * data)283 static 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(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(gt_psv_bck);
334 break;
335 default:
336 return NOTIFY_DONE;
337 }
338
339 return NOTIFY_DONE;
340 }
341
global_timer_of_register(struct device_node * np)342 static 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;
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(np, 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(np, 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, 0);
372 if (!IS_ERR(gt_clk)) {
373 err = clk_prepare_enable(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(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(gt_clk, >_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(gt_ppi, gt_clockevent_interrupt,
400 "gt", 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(CPUHP_AP_ARM_GLOBAL_TIMER_STARTING,
413 "clockevents/arm/global_timer:starting",
414 gt_starting_cpu, gt_dying_cpu);
415 if (err)
416 goto out_irq;
417
418 gt_delay_timer_init();
419
420 return 0;
421
422 out_irq:
423 free_percpu_irq(gt_ppi, gt_evt);
424 out_free:
425 free_percpu(gt_evt);
426 out_clk_nb:
427 clk_notifier_unregister(gt_clk, >_clk_rate_change_nb);
428 out_clk:
429 clk_disable_unprepare(gt_clk);
430 out_unmap:
431 iounmap(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 */
438 TIMER_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
439 global_timer_of_register);
440