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1// SPDX-License-Identifier: GPL-2.0
2#include <linux/init.h>
3#include <linux/clocksource.h>
4#include <linux/clockchips.h>
5#include <linux/interrupt.h>
6#include <linux/irq.h>
7
8#include <linux/clk.h>
9#include <linux/delay.h>
10#include <linux/err.h>
11#include <linux/ioport.h>
12#include <linux/io.h>
13#include <linux/of_address.h>
14#include <linux/of_irq.h>
15#include <linux/sched_clock.h>
16#include <linux/syscore_ops.h>
17#include <soc/at91/atmel_tcb.h>
18
19
20/*
21 * We're configured to use a specific TC block, one that's not hooked
22 * up to external hardware, to provide a time solution:
23 *
24 * - Two channels combine to create a free-running 32 bit counter
25 * with a base rate of 5+ MHz, packaged as a clocksource (with
26 * resolution better than 200 nsec).
27 * - Some chips support 32 bit counter. A single channel is used for
28 * this 32 bit free-running counter. the second channel is not used.
29 *
30 * - The third channel may be used to provide a 16-bit clockevent
31 * source, used in either periodic or oneshot mode. This runs
32 * at 32 KiHZ, and can handle delays of up to two seconds.
33 *
34 * REVISIT behavior during system suspend states... we should disable
35 * all clocks and save the power. Easily done for clockevent devices,
36 * but clocksources won't necessarily get the needed notifications.
37 * For deeper system sleep states, this will be mandatory...
38 */
39
40static void __iomem *tcaddr;
41static struct
42{
43 u32 cmr;
44 u32 imr;
45 u32 rc;
46 bool clken;
47} tcb_cache[3];
48static u32 bmr_cache;
49
50static u64 tc_get_cycles(struct clocksource *cs)
51{
52 unsigned long flags;
53 u32 lower, upper;
54
55 raw_local_irq_save(flags);
56 do {
57 upper = readl_relaxed(tcaddr + ATMEL_TC_REG(1, CV));
58 lower = readl_relaxed(tcaddr + ATMEL_TC_REG(0, CV));
59 } while (upper != readl_relaxed(tcaddr + ATMEL_TC_REG(1, CV)));
60
61 raw_local_irq_restore(flags);
62 return (upper << 16) | lower;
63}
64
65static u64 tc_get_cycles32(struct clocksource *cs)
66{
67 return readl_relaxed(tcaddr + ATMEL_TC_REG(0, CV));
68}
69
70static void tc_clksrc_suspend(struct clocksource *cs)
71{
72 int i;
73
74 for (i = 0; i < ARRAY_SIZE(tcb_cache); i++) {
75 tcb_cache[i].cmr = readl(tcaddr + ATMEL_TC_REG(i, CMR));
76 tcb_cache[i].imr = readl(tcaddr + ATMEL_TC_REG(i, IMR));
77 tcb_cache[i].rc = readl(tcaddr + ATMEL_TC_REG(i, RC));
78 tcb_cache[i].clken = !!(readl(tcaddr + ATMEL_TC_REG(i, SR)) &
79 ATMEL_TC_CLKSTA);
80 }
81
82 bmr_cache = readl(tcaddr + ATMEL_TC_BMR);
83}
84
85static void tc_clksrc_resume(struct clocksource *cs)
86{
87 int i;
88
89 for (i = 0; i < ARRAY_SIZE(tcb_cache); i++) {
90 /* Restore registers for the channel, RA and RB are not used */
91 writel(tcb_cache[i].cmr, tcaddr + ATMEL_TC_REG(i, CMR));
92 writel(tcb_cache[i].rc, tcaddr + ATMEL_TC_REG(i, RC));
93 writel(0, tcaddr + ATMEL_TC_REG(i, RA));
94 writel(0, tcaddr + ATMEL_TC_REG(i, RB));
95 /* Disable all the interrupts */
96 writel(0xff, tcaddr + ATMEL_TC_REG(i, IDR));
97 /* Reenable interrupts that were enabled before suspending */
98 writel(tcb_cache[i].imr, tcaddr + ATMEL_TC_REG(i, IER));
99 /* Start the clock if it was used */
100 if (tcb_cache[i].clken)
101 writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(i, CCR));
102 }
103
104 /* Dual channel, chain channels */
105 writel(bmr_cache, tcaddr + ATMEL_TC_BMR);
106 /* Finally, trigger all the channels*/
107 writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
108}
109
110static struct clocksource clksrc = {
111 .rating = 200,
112 .read = tc_get_cycles,
113 .mask = CLOCKSOURCE_MASK(32),
114 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
115 .suspend = tc_clksrc_suspend,
116 .resume = tc_clksrc_resume,
117};
118
119static u64 notrace tc_sched_clock_read(void)
120{
121 return tc_get_cycles(&clksrc);
122}
123
124static u64 notrace tc_sched_clock_read32(void)
125{
126 return tc_get_cycles32(&clksrc);
127}
128
129static struct delay_timer tc_delay_timer;
130
131static unsigned long tc_delay_timer_read(void)
132{
133 return tc_get_cycles(&clksrc);
134}
135
136static unsigned long notrace tc_delay_timer_read32(void)
137{
138 return tc_get_cycles32(&clksrc);
139}
140
141#ifdef CONFIG_GENERIC_CLOCKEVENTS
142
143struct tc_clkevt_device {
144 struct clock_event_device clkevt;
145 struct clk *clk;
146 void __iomem *regs;
147};
148
149static struct tc_clkevt_device *to_tc_clkevt(struct clock_event_device *clkevt)
150{
151 return container_of(clkevt, struct tc_clkevt_device, clkevt);
152}
153
154/* For now, we always use the 32K clock ... this optimizes for NO_HZ,
155 * because using one of the divided clocks would usually mean the
156 * tick rate can never be less than several dozen Hz (vs 0.5 Hz).
157 *
158 * A divided clock could be good for high resolution timers, since
159 * 30.5 usec resolution can seem "low".
160 */
161static u32 timer_clock;
162
163static int tc_shutdown(struct clock_event_device *d)
164{
165 struct tc_clkevt_device *tcd = to_tc_clkevt(d);
166 void __iomem *regs = tcd->regs;
167
168 writel(0xff, regs + ATMEL_TC_REG(2, IDR));
169 writel(ATMEL_TC_CLKDIS, regs + ATMEL_TC_REG(2, CCR));
170 if (!clockevent_state_detached(d))
171 clk_disable(tcd->clk);
172
173 return 0;
174}
175
176static int tc_set_oneshot(struct clock_event_device *d)
177{
178 struct tc_clkevt_device *tcd = to_tc_clkevt(d);
179 void __iomem *regs = tcd->regs;
180
181 if (clockevent_state_oneshot(d) || clockevent_state_periodic(d))
182 tc_shutdown(d);
183
184 clk_enable(tcd->clk);
185
186 /* slow clock, count up to RC, then irq and stop */
187 writel(timer_clock | ATMEL_TC_CPCSTOP | ATMEL_TC_WAVE |
188 ATMEL_TC_WAVESEL_UP_AUTO, regs + ATMEL_TC_REG(2, CMR));
189 writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
190
191 /* set_next_event() configures and starts the timer */
192 return 0;
193}
194
195static int tc_set_periodic(struct clock_event_device *d)
196{
197 struct tc_clkevt_device *tcd = to_tc_clkevt(d);
198 void __iomem *regs = tcd->regs;
199
200 if (clockevent_state_oneshot(d) || clockevent_state_periodic(d))
201 tc_shutdown(d);
202
203 /* By not making the gentime core emulate periodic mode on top
204 * of oneshot, we get lower overhead and improved accuracy.
205 */
206 clk_enable(tcd->clk);
207
208 /* slow clock, count up to RC, then irq and restart */
209 writel(timer_clock | ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
210 regs + ATMEL_TC_REG(2, CMR));
211 writel((32768 + HZ / 2) / HZ, tcaddr + ATMEL_TC_REG(2, RC));
212
213 /* Enable clock and interrupts on RC compare */
214 writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
215
216 /* go go gadget! */
217 writel(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG, regs +
218 ATMEL_TC_REG(2, CCR));
219 return 0;
220}
221
222static int tc_next_event(unsigned long delta, struct clock_event_device *d)
223{
224 writel_relaxed(delta, tcaddr + ATMEL_TC_REG(2, RC));
225
226 /* go go gadget! */
227 writel_relaxed(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG,
228 tcaddr + ATMEL_TC_REG(2, CCR));
229 return 0;
230}
231
232static struct tc_clkevt_device clkevt = {
233 .clkevt = {
234 .features = CLOCK_EVT_FEAT_PERIODIC |
235 CLOCK_EVT_FEAT_ONESHOT,
236 /* Should be lower than at91rm9200's system timer */
237 .rating = 125,
238 .set_next_event = tc_next_event,
239 .set_state_shutdown = tc_shutdown,
240 .set_state_periodic = tc_set_periodic,
241 .set_state_oneshot = tc_set_oneshot,
242 },
243};
244
245static irqreturn_t ch2_irq(int irq, void *handle)
246{
247 struct tc_clkevt_device *dev = handle;
248 unsigned int sr;
249
250 sr = readl_relaxed(dev->regs + ATMEL_TC_REG(2, SR));
251 if (sr & ATMEL_TC_CPCS) {
252 dev->clkevt.event_handler(&dev->clkevt);
253 return IRQ_HANDLED;
254 }
255
256 return IRQ_NONE;
257}
258
259static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
260{
261 int ret;
262 struct clk *t2_clk = tc->clk[2];
263 int irq = tc->irq[2];
264
265 ret = clk_prepare_enable(tc->slow_clk);
266 if (ret)
267 return ret;
268
269 /* try to enable t2 clk to avoid future errors in mode change */
270 ret = clk_prepare_enable(t2_clk);
271 if (ret) {
272 clk_disable_unprepare(tc->slow_clk);
273 return ret;
274 }
275
276 clk_disable(t2_clk);
277
278 clkevt.regs = tc->regs;
279 clkevt.clk = t2_clk;
280
281 timer_clock = clk32k_divisor_idx;
282
283 clkevt.clkevt.cpumask = cpumask_of(0);
284
285 ret = request_irq(irq, ch2_irq, IRQF_TIMER, "tc_clkevt", &clkevt);
286 if (ret) {
287 clk_unprepare(t2_clk);
288 clk_disable_unprepare(tc->slow_clk);
289 return ret;
290 }
291
292 clockevents_config_and_register(&clkevt.clkevt, 32768, 1, 0xffff);
293
294 return ret;
295}
296
297#else /* !CONFIG_GENERIC_CLOCKEVENTS */
298
299static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
300{
301 /* NOTHING */
302 return 0;
303}
304
305#endif
306
307static void __init tcb_setup_dual_chan(struct atmel_tc *tc, int mck_divisor_idx)
308{
309 /* channel 0: waveform mode, input mclk/8, clock TIOA0 on overflow */
310 writel(mck_divisor_idx /* likely divide-by-8 */
311 | ATMEL_TC_WAVE
312 | ATMEL_TC_WAVESEL_UP /* free-run */
313 | ATMEL_TC_ACPA_SET /* TIOA0 rises at 0 */
314 | ATMEL_TC_ACPC_CLEAR, /* (duty cycle 50%) */
315 tcaddr + ATMEL_TC_REG(0, CMR));
316 writel(0x0000, tcaddr + ATMEL_TC_REG(0, RA));
317 writel(0x8000, tcaddr + ATMEL_TC_REG(0, RC));
318 writel(0xff, tcaddr + ATMEL_TC_REG(0, IDR)); /* no irqs */
319 writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(0, CCR));
320
321 /* channel 1: waveform mode, input TIOA0 */
322 writel(ATMEL_TC_XC1 /* input: TIOA0 */
323 | ATMEL_TC_WAVE
324 | ATMEL_TC_WAVESEL_UP, /* free-run */
325 tcaddr + ATMEL_TC_REG(1, CMR));
326 writel(0xff, tcaddr + ATMEL_TC_REG(1, IDR)); /* no irqs */
327 writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(1, CCR));
328
329 /* chain channel 0 to channel 1*/
330 writel(ATMEL_TC_TC1XC1S_TIOA0, tcaddr + ATMEL_TC_BMR);
331 /* then reset all the timers */
332 writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
333}
334
335static void __init tcb_setup_single_chan(struct atmel_tc *tc, int mck_divisor_idx)
336{
337 /* channel 0: waveform mode, input mclk/8 */
338 writel(mck_divisor_idx /* likely divide-by-8 */
339 | ATMEL_TC_WAVE
340 | ATMEL_TC_WAVESEL_UP, /* free-run */
341 tcaddr + ATMEL_TC_REG(0, CMR));
342 writel(0xff, tcaddr + ATMEL_TC_REG(0, IDR)); /* no irqs */
343 writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(0, CCR));
344
345 /* then reset all the timers */
346 writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
347}
348
349static const u8 atmel_tcb_divisors[5] = { 2, 8, 32, 128, 0, };
350
351static const struct of_device_id atmel_tcb_of_match[] = {
352 { .compatible = "atmel,at91rm9200-tcb", .data = (void *)16, },
353 { .compatible = "atmel,at91sam9x5-tcb", .data = (void *)32, },
354 { /* sentinel */ }
355};
356
357static int __init tcb_clksrc_init(struct device_node *node)
358{
359 struct atmel_tc tc;
360 struct clk *t0_clk;
361 const struct of_device_id *match;
362 u64 (*tc_sched_clock)(void);
363 u32 rate, divided_rate = 0;
364 int best_divisor_idx = -1;
365 int clk32k_divisor_idx = -1;
366 int bits;
367 int i;
368 int ret;
369
370 /* Protect against multiple calls */
371 if (tcaddr)
372 return 0;
373
374 tc.regs = of_iomap(node->parent, 0);
375 if (!tc.regs)
376 return -ENXIO;
377
378 t0_clk = of_clk_get_by_name(node->parent, "t0_clk");
379 if (IS_ERR(t0_clk))
380 return PTR_ERR(t0_clk);
381
382 tc.slow_clk = of_clk_get_by_name(node->parent, "slow_clk");
383 if (IS_ERR(tc.slow_clk))
384 return PTR_ERR(tc.slow_clk);
385
386 tc.clk[0] = t0_clk;
387 tc.clk[1] = of_clk_get_by_name(node->parent, "t1_clk");
388 if (IS_ERR(tc.clk[1]))
389 tc.clk[1] = t0_clk;
390 tc.clk[2] = of_clk_get_by_name(node->parent, "t2_clk");
391 if (IS_ERR(tc.clk[2]))
392 tc.clk[2] = t0_clk;
393
394 tc.irq[2] = of_irq_get(node->parent, 2);
395 if (tc.irq[2] <= 0) {
396 tc.irq[2] = of_irq_get(node->parent, 0);
397 if (tc.irq[2] <= 0)
398 return -EINVAL;
399 }
400
401 match = of_match_node(atmel_tcb_of_match, node->parent);
402 bits = (uintptr_t)match->data;
403
404 for (i = 0; i < ARRAY_SIZE(tc.irq); i++)
405 writel(ATMEL_TC_ALL_IRQ, tc.regs + ATMEL_TC_REG(i, IDR));
406
407 ret = clk_prepare_enable(t0_clk);
408 if (ret) {
409 pr_debug("can't enable T0 clk\n");
410 return ret;
411 }
412
413 /* How fast will we be counting? Pick something over 5 MHz. */
414 rate = (u32) clk_get_rate(t0_clk);
415 for (i = 0; i < ARRAY_SIZE(atmel_tcb_divisors); i++) {
416 unsigned divisor = atmel_tcb_divisors[i];
417 unsigned tmp;
418
419 /* remember 32 KiHz clock for later */
420 if (!divisor) {
421 clk32k_divisor_idx = i;
422 continue;
423 }
424
425 tmp = rate / divisor;
426 pr_debug("TC: %u / %-3u [%d] --> %u\n", rate, divisor, i, tmp);
427 if (best_divisor_idx > 0) {
428 if (tmp < 5 * 1000 * 1000)
429 continue;
430 }
431 divided_rate = tmp;
432 best_divisor_idx = i;
433 }
434
435 clksrc.name = kbasename(node->parent->full_name);
436 clkevt.clkevt.name = kbasename(node->parent->full_name);
437 pr_debug("%s at %d.%03d MHz\n", clksrc.name, divided_rate / 1000000,
438 ((divided_rate % 1000000) + 500) / 1000);
439
440 tcaddr = tc.regs;
441
442 if (bits == 32) {
443 /* use apropriate function to read 32 bit counter */
444 clksrc.read = tc_get_cycles32;
445 /* setup ony channel 0 */
446 tcb_setup_single_chan(&tc, best_divisor_idx);
447 tc_sched_clock = tc_sched_clock_read32;
448 tc_delay_timer.read_current_timer = tc_delay_timer_read32;
449 } else {
450 /* we have three clocks no matter what the
451 * underlying platform supports.
452 */
453 ret = clk_prepare_enable(tc.clk[1]);
454 if (ret) {
455 pr_debug("can't enable T1 clk\n");
456 goto err_disable_t0;
457 }
458 /* setup both channel 0 & 1 */
459 tcb_setup_dual_chan(&tc, best_divisor_idx);
460 tc_sched_clock = tc_sched_clock_read;
461 tc_delay_timer.read_current_timer = tc_delay_timer_read;
462 }
463
464 /* and away we go! */
465 ret = clocksource_register_hz(&clksrc, divided_rate);
466 if (ret)
467 goto err_disable_t1;
468
469 /* channel 2: periodic and oneshot timer support */
470 ret = setup_clkevents(&tc, clk32k_divisor_idx);
471 if (ret)
472 goto err_unregister_clksrc;
473
474 sched_clock_register(tc_sched_clock, 32, divided_rate);
475
476 tc_delay_timer.freq = divided_rate;
477 register_current_timer_delay(&tc_delay_timer);
478
479 return 0;
480
481err_unregister_clksrc:
482 clocksource_unregister(&clksrc);
483
484err_disable_t1:
485 if (bits != 32)
486 clk_disable_unprepare(tc.clk[1]);
487
488err_disable_t0:
489 clk_disable_unprepare(t0_clk);
490
491 tcaddr = NULL;
492
493 return ret;
494}
495TIMER_OF_DECLARE(atmel_tcb_clksrc, "atmel,tcb-timer", tcb_clksrc_init);