xref: /linux/drivers/clocksource/timer-atmel-tcb.c (revision 0ea5c948cb64bab5bc7a5516774eb8536f05aa0d)
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 clockevent source, used in
31  *   either periodic or oneshot mode. For 16-bit counter its runs at 32 KiHZ,
32  *   and can handle delays of up to two seconds. For 32-bit counters, it runs at
33  *   the same rate as the clocksource
34  *
35  * REVISIT behavior during system suspend states... we should disable
36  * all clocks and save the power.  Easily done for clockevent devices,
37  * but clocksources won't necessarily get the needed notifications.
38  * For deeper system sleep states, this will be mandatory...
39  */
40 
41 static void __iomem *tcaddr;
42 static struct
43 {
44 	u32 cmr;
45 	u32 imr;
46 	u32 rc;
47 	bool clken;
48 } tcb_cache[3];
49 static u32 bmr_cache;
50 
51 static const u8 atmel_tcb_divisors[] = { 2, 8, 32, 128 };
52 
tc_get_cycles(struct clocksource * cs)53 static u64 tc_get_cycles(struct clocksource *cs)
54 {
55 	unsigned long	flags;
56 	u32		lower, upper;
57 
58 	raw_local_irq_save(flags);
59 	do {
60 		upper = readl_relaxed(tcaddr + ATMEL_TC_REG(1, CV));
61 		lower = readl_relaxed(tcaddr + ATMEL_TC_REG(0, CV));
62 	} while (upper != readl_relaxed(tcaddr + ATMEL_TC_REG(1, CV)));
63 
64 	raw_local_irq_restore(flags);
65 	return (upper << 16) | lower;
66 }
67 
tc_get_cycles32(struct clocksource * cs)68 static u64 tc_get_cycles32(struct clocksource *cs)
69 {
70 	return readl_relaxed(tcaddr + ATMEL_TC_REG(0, CV));
71 }
72 
tc_clksrc_suspend(struct clocksource * cs)73 static void tc_clksrc_suspend(struct clocksource *cs)
74 {
75 	int i;
76 
77 	for (i = 0; i < ARRAY_SIZE(tcb_cache); i++) {
78 		tcb_cache[i].cmr = readl(tcaddr + ATMEL_TC_REG(i, CMR));
79 		tcb_cache[i].imr = readl(tcaddr + ATMEL_TC_REG(i, IMR));
80 		tcb_cache[i].rc = readl(tcaddr + ATMEL_TC_REG(i, RC));
81 		tcb_cache[i].clken = !!(readl(tcaddr + ATMEL_TC_REG(i, SR)) &
82 					ATMEL_TC_CLKSTA);
83 	}
84 
85 	bmr_cache = readl(tcaddr + ATMEL_TC_BMR);
86 }
87 
tc_clksrc_resume(struct clocksource * cs)88 static void tc_clksrc_resume(struct clocksource *cs)
89 {
90 	int i;
91 
92 	for (i = 0; i < ARRAY_SIZE(tcb_cache); i++) {
93 		/* Restore registers for the channel, RA and RB are not used  */
94 		writel(tcb_cache[i].cmr, tcaddr + ATMEL_TC_REG(i, CMR));
95 		writel(tcb_cache[i].rc, tcaddr + ATMEL_TC_REG(i, RC));
96 		writel(0, tcaddr + ATMEL_TC_REG(i, RA));
97 		writel(0, tcaddr + ATMEL_TC_REG(i, RB));
98 		/* Disable all the interrupts */
99 		writel(0xff, tcaddr + ATMEL_TC_REG(i, IDR));
100 		/* Reenable interrupts that were enabled before suspending */
101 		writel(tcb_cache[i].imr, tcaddr + ATMEL_TC_REG(i, IER));
102 		/* Start the clock if it was used */
103 		if (tcb_cache[i].clken)
104 			writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(i, CCR));
105 	}
106 
107 	/* Dual channel, chain channels */
108 	writel(bmr_cache, tcaddr + ATMEL_TC_BMR);
109 	/* Finally, trigger all the channels*/
110 	writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
111 }
112 
113 static struct clocksource clksrc = {
114 	.rating         = 200,
115 	.read           = tc_get_cycles,
116 	.mask           = CLOCKSOURCE_MASK(32),
117 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
118 	.suspend	= tc_clksrc_suspend,
119 	.resume		= tc_clksrc_resume,
120 };
121 
tc_sched_clock_read(void)122 static u64 notrace tc_sched_clock_read(void)
123 {
124 	return tc_get_cycles(&clksrc);
125 }
126 
tc_sched_clock_read32(void)127 static u64 notrace tc_sched_clock_read32(void)
128 {
129 	return tc_get_cycles32(&clksrc);
130 }
131 
132 static struct delay_timer tc_delay_timer;
133 
tc_delay_timer_read(void)134 static unsigned long tc_delay_timer_read(void)
135 {
136 	return tc_get_cycles(&clksrc);
137 }
138 
tc_delay_timer_read32(void)139 static unsigned long notrace tc_delay_timer_read32(void)
140 {
141 	return tc_get_cycles32(&clksrc);
142 }
143 
144 #ifdef CONFIG_GENERIC_CLOCKEVENTS
145 
146 struct tc_clkevt_device {
147 	struct clock_event_device	clkevt;
148 	struct clk			*clk;
149 	u32				rate;
150 	void __iomem			*regs;
151 };
152 
to_tc_clkevt(struct clock_event_device * clkevt)153 static struct tc_clkevt_device *to_tc_clkevt(struct clock_event_device *clkevt)
154 {
155 	return container_of(clkevt, struct tc_clkevt_device, clkevt);
156 }
157 
158 static u32 timer_clock;
159 
tc_shutdown(struct clock_event_device * d)160 static int tc_shutdown(struct clock_event_device *d)
161 {
162 	struct tc_clkevt_device *tcd = to_tc_clkevt(d);
163 	void __iomem		*regs = tcd->regs;
164 
165 	writel(0xff, regs + ATMEL_TC_REG(2, IDR));
166 	writel(ATMEL_TC_CLKDIS, regs + ATMEL_TC_REG(2, CCR));
167 	if (!clockevent_state_detached(d))
168 		clk_disable(tcd->clk);
169 
170 	return 0;
171 }
172 
tc_set_oneshot(struct clock_event_device * d)173 static int tc_set_oneshot(struct clock_event_device *d)
174 {
175 	struct tc_clkevt_device *tcd = to_tc_clkevt(d);
176 	void __iomem		*regs = tcd->regs;
177 
178 	if (clockevent_state_oneshot(d) || clockevent_state_periodic(d))
179 		tc_shutdown(d);
180 
181 	clk_enable(tcd->clk);
182 
183 	/* count up to RC, then irq and stop */
184 	writel(timer_clock | ATMEL_TC_CPCSTOP | ATMEL_TC_WAVE |
185 		     ATMEL_TC_WAVESEL_UP_AUTO, regs + ATMEL_TC_REG(2, CMR));
186 	writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
187 
188 	/* set_next_event() configures and starts the timer */
189 	return 0;
190 }
191 
tc_set_periodic(struct clock_event_device * d)192 static int tc_set_periodic(struct clock_event_device *d)
193 {
194 	struct tc_clkevt_device *tcd = to_tc_clkevt(d);
195 	void __iomem		*regs = tcd->regs;
196 
197 	if (clockevent_state_oneshot(d) || clockevent_state_periodic(d))
198 		tc_shutdown(d);
199 
200 	/* By not making the gentime core emulate periodic mode on top
201 	 * of oneshot, we get lower overhead and improved accuracy.
202 	 */
203 	clk_enable(tcd->clk);
204 
205 	/* count up to RC, then irq and restart */
206 	writel(timer_clock | ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
207 		     regs + ATMEL_TC_REG(2, CMR));
208 	writel((tcd->rate + HZ / 2) / HZ, tcaddr + ATMEL_TC_REG(2, RC));
209 
210 	/* Enable clock and interrupts on RC compare */
211 	writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
212 
213 	/* go go gadget! */
214 	writel(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG, regs +
215 		     ATMEL_TC_REG(2, CCR));
216 	return 0;
217 }
218 
tc_next_event(unsigned long delta,struct clock_event_device * d)219 static int tc_next_event(unsigned long delta, struct clock_event_device *d)
220 {
221 	writel_relaxed(delta, tcaddr + ATMEL_TC_REG(2, RC));
222 
223 	/* go go gadget! */
224 	writel_relaxed(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG,
225 			tcaddr + ATMEL_TC_REG(2, CCR));
226 	return 0;
227 }
228 
229 static struct tc_clkevt_device clkevt = {
230 	.clkevt	= {
231 		.features		= CLOCK_EVT_FEAT_PERIODIC |
232 					  CLOCK_EVT_FEAT_ONESHOT,
233 		/* Should be lower than at91rm9200's system timer */
234 		.rating			= 125,
235 		.set_next_event		= tc_next_event,
236 		.set_state_shutdown	= tc_shutdown,
237 		.set_state_periodic	= tc_set_periodic,
238 		.set_state_oneshot	= tc_set_oneshot,
239 	},
240 };
241 
ch2_irq(int irq,void * handle)242 static irqreturn_t ch2_irq(int irq, void *handle)
243 {
244 	struct tc_clkevt_device	*dev = handle;
245 	unsigned int		sr;
246 
247 	sr = readl_relaxed(dev->regs + ATMEL_TC_REG(2, SR));
248 	if (sr & ATMEL_TC_CPCS) {
249 		dev->clkevt.event_handler(&dev->clkevt);
250 		return IRQ_HANDLED;
251 	}
252 
253 	return IRQ_NONE;
254 }
255 
setup_clkevents(struct atmel_tc * tc,int divisor_idx)256 static int __init setup_clkevents(struct atmel_tc *tc, int divisor_idx)
257 {
258 	int ret;
259 	struct clk *t2_clk = tc->clk[2];
260 	int irq = tc->irq[2];
261 	int bits = tc->tcb_config->counter_width;
262 
263 	/* try to enable t2 clk to avoid future errors in mode change */
264 	ret = clk_prepare_enable(t2_clk);
265 	if (ret)
266 		return ret;
267 
268 	clkevt.regs = tc->regs;
269 	clkevt.clk = t2_clk;
270 
271 	if (bits == 32) {
272 		timer_clock = divisor_idx;
273 		clkevt.rate = clk_get_rate(t2_clk) / atmel_tcb_divisors[divisor_idx];
274 	} else {
275 		ret = clk_prepare_enable(tc->slow_clk);
276 		if (ret) {
277 			clk_disable_unprepare(t2_clk);
278 			return ret;
279 		}
280 
281 		clkevt.rate = clk_get_rate(tc->slow_clk);
282 		timer_clock = ATMEL_TC_TIMER_CLOCK5;
283 	}
284 
285 	clk_disable(t2_clk);
286 
287 	clkevt.clkevt.cpumask = cpumask_of(0);
288 
289 	ret = request_irq(irq, ch2_irq, IRQF_TIMER, "tc_clkevt", &clkevt);
290 	if (ret) {
291 		clk_unprepare(t2_clk);
292 		if (bits != 32)
293 			clk_disable_unprepare(tc->slow_clk);
294 		return ret;
295 	}
296 
297 	clockevents_config_and_register(&clkevt.clkevt, clkevt.rate, 1, BIT(bits) - 1);
298 
299 	return ret;
300 }
301 
302 #else /* !CONFIG_GENERIC_CLOCKEVENTS */
303 
setup_clkevents(struct atmel_tc * tc,int divisor_idx)304 static int __init setup_clkevents(struct atmel_tc *tc, int divisor_idx)
305 {
306 	/* NOTHING */
307 	return 0;
308 }
309 
310 #endif
311 
tcb_setup_dual_chan(struct atmel_tc * tc,int mck_divisor_idx)312 static void __init tcb_setup_dual_chan(struct atmel_tc *tc, int mck_divisor_idx)
313 {
314 	/* channel 0:  waveform mode, input mclk/8, clock TIOA0 on overflow */
315 	writel(mck_divisor_idx			/* likely divide-by-8 */
316 			| ATMEL_TC_WAVE
317 			| ATMEL_TC_WAVESEL_UP		/* free-run */
318 			| ATMEL_TC_ASWTRG_SET		/* TIOA0 rises at software trigger */
319 			| ATMEL_TC_ACPA_SET		/* TIOA0 rises at 0 */
320 			| ATMEL_TC_ACPC_CLEAR,		/* (duty cycle 50%) */
321 			tcaddr + ATMEL_TC_REG(0, CMR));
322 	writel(0x0000, tcaddr + ATMEL_TC_REG(0, RA));
323 	writel(0x8000, tcaddr + ATMEL_TC_REG(0, RC));
324 	writel(0xff, tcaddr + ATMEL_TC_REG(0, IDR));	/* no irqs */
325 	writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(0, CCR));
326 
327 	/* channel 1:  waveform mode, input TIOA0 */
328 	writel(ATMEL_TC_XC1			/* input: TIOA0 */
329 			| ATMEL_TC_WAVE
330 			| ATMEL_TC_WAVESEL_UP,		/* free-run */
331 			tcaddr + ATMEL_TC_REG(1, CMR));
332 	writel(0xff, tcaddr + ATMEL_TC_REG(1, IDR));	/* no irqs */
333 	writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(1, CCR));
334 
335 	/* chain channel 0 to channel 1*/
336 	writel(ATMEL_TC_TC1XC1S_TIOA0, tcaddr + ATMEL_TC_BMR);
337 	/* then reset all the timers */
338 	writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
339 }
340 
tcb_setup_single_chan(struct atmel_tc * tc,int mck_divisor_idx)341 static void __init tcb_setup_single_chan(struct atmel_tc *tc, int mck_divisor_idx)
342 {
343 	/* channel 0:  waveform mode, input mclk/8 */
344 	writel(mck_divisor_idx			/* likely divide-by-8 */
345 			| ATMEL_TC_WAVE
346 			| ATMEL_TC_WAVESEL_UP,		/* free-run */
347 			tcaddr + ATMEL_TC_REG(0, CMR));
348 	writel(0xff, tcaddr + ATMEL_TC_REG(0, IDR));	/* no irqs */
349 	writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(0, CCR));
350 
351 	/* then reset all the timers */
352 	writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
353 }
354 
355 static struct atmel_tcb_config tcb_rm9200_config = {
356 	.counter_width = 16,
357 };
358 
359 static struct atmel_tcb_config tcb_sam9x5_config = {
360 	.counter_width = 32,
361 };
362 
363 static struct atmel_tcb_config tcb_sama5d2_config = {
364 	.counter_width = 32,
365 	.has_gclk = 1,
366 };
367 
368 static const struct of_device_id atmel_tcb_of_match[] = {
369 	{ .compatible = "atmel,at91rm9200-tcb", .data = &tcb_rm9200_config, },
370 	{ .compatible = "atmel,at91sam9x5-tcb", .data = &tcb_sam9x5_config, },
371 	{ .compatible = "atmel,sama5d2-tcb", .data = &tcb_sama5d2_config, },
372 	{ /* sentinel */ }
373 };
374 
tcb_clksrc_init(struct device_node * node)375 static int __init tcb_clksrc_init(struct device_node *node)
376 {
377 	struct atmel_tc tc;
378 	struct clk *t0_clk;
379 	const struct of_device_id *match;
380 	u64 (*tc_sched_clock)(void);
381 	u32 rate, divided_rate = 0;
382 	int best_divisor_idx = -1;
383 	int bits;
384 	int i;
385 	int ret;
386 
387 	/* Protect against multiple calls */
388 	if (tcaddr)
389 		return 0;
390 
391 	tc.regs = of_iomap(node->parent, 0);
392 	if (!tc.regs)
393 		return -ENXIO;
394 
395 	t0_clk = of_clk_get_by_name(node->parent, "t0_clk");
396 	if (IS_ERR(t0_clk))
397 		return PTR_ERR(t0_clk);
398 
399 	tc.slow_clk = of_clk_get_by_name(node->parent, "slow_clk");
400 	if (IS_ERR(tc.slow_clk))
401 		return PTR_ERR(tc.slow_clk);
402 
403 	tc.clk[0] = t0_clk;
404 	tc.clk[1] = of_clk_get_by_name(node->parent, "t1_clk");
405 	if (IS_ERR(tc.clk[1]))
406 		tc.clk[1] = t0_clk;
407 	tc.clk[2] = of_clk_get_by_name(node->parent, "t2_clk");
408 	if (IS_ERR(tc.clk[2]))
409 		tc.clk[2] = t0_clk;
410 
411 	tc.irq[2] = of_irq_get(node->parent, 2);
412 	if (tc.irq[2] <= 0) {
413 		tc.irq[2] = of_irq_get(node->parent, 0);
414 		if (tc.irq[2] <= 0)
415 			return -EINVAL;
416 	}
417 
418 	match = of_match_node(atmel_tcb_of_match, node->parent);
419 	if (!match)
420 		return -ENODEV;
421 
422 	tc.tcb_config = match->data;
423 	bits = tc.tcb_config->counter_width;
424 
425 	for (i = 0; i < ARRAY_SIZE(tc.irq); i++)
426 		writel(ATMEL_TC_ALL_IRQ, tc.regs + ATMEL_TC_REG(i, IDR));
427 
428 	ret = clk_prepare_enable(t0_clk);
429 	if (ret) {
430 		pr_debug("can't enable T0 clk\n");
431 		return ret;
432 	}
433 
434 	/* How fast will we be counting?  Pick something over 5 MHz.  */
435 	rate = (u32) clk_get_rate(t0_clk);
436 	i = 0;
437 	if (tc.tcb_config->has_gclk)
438 		i = 1;
439 	for (; i < ARRAY_SIZE(atmel_tcb_divisors); i++) {
440 		unsigned divisor = atmel_tcb_divisors[i];
441 		unsigned tmp;
442 
443 		tmp = rate / divisor;
444 		pr_debug("TC: %u / %-3u [%d] --> %u\n", rate, divisor, i, tmp);
445 		if ((best_divisor_idx >= 0) && (tmp < 5 * 1000 * 1000))
446 			break;
447 		divided_rate = tmp;
448 		best_divisor_idx = i;
449 	}
450 
451 	clksrc.name = kbasename(node->parent->full_name);
452 	clkevt.clkevt.name = kbasename(node->parent->full_name);
453 	pr_debug("%s at %d.%03d MHz\n", clksrc.name, divided_rate / 1000000,
454 			((divided_rate % 1000000) + 500) / 1000);
455 
456 	tcaddr = tc.regs;
457 
458 	if (bits == 32) {
459 		/* use appropriate function to read 32 bit counter */
460 		clksrc.read = tc_get_cycles32;
461 		/* setup only channel 0 */
462 		tcb_setup_single_chan(&tc, best_divisor_idx);
463 		tc_sched_clock = tc_sched_clock_read32;
464 		tc_delay_timer.read_current_timer = tc_delay_timer_read32;
465 	} else {
466 		/* we have three clocks no matter what the
467 		 * underlying platform supports.
468 		 */
469 		ret = clk_prepare_enable(tc.clk[1]);
470 		if (ret) {
471 			pr_debug("can't enable T1 clk\n");
472 			goto err_disable_t0;
473 		}
474 		/* setup both channel 0 & 1 */
475 		tcb_setup_dual_chan(&tc, best_divisor_idx);
476 		tc_sched_clock = tc_sched_clock_read;
477 		tc_delay_timer.read_current_timer = tc_delay_timer_read;
478 	}
479 
480 	/* and away we go! */
481 	ret = clocksource_register_hz(&clksrc, divided_rate);
482 	if (ret)
483 		goto err_disable_t1;
484 
485 	/* channel 2:  periodic and oneshot timer support */
486 	ret = setup_clkevents(&tc, best_divisor_idx);
487 	if (ret)
488 		goto err_unregister_clksrc;
489 
490 	sched_clock_register(tc_sched_clock, 32, divided_rate);
491 
492 	tc_delay_timer.freq = divided_rate;
493 	register_current_timer_delay(&tc_delay_timer);
494 
495 	return 0;
496 
497 err_unregister_clksrc:
498 	clocksource_unregister(&clksrc);
499 
500 err_disable_t1:
501 	if (bits != 32)
502 		clk_disable_unprepare(tc.clk[1]);
503 
504 err_disable_t0:
505 	clk_disable_unprepare(t0_clk);
506 
507 	tcaddr = NULL;
508 
509 	return ret;
510 }
511 TIMER_OF_DECLARE(atmel_tcb_clksrc, "atmel,tcb-timer", tcb_clksrc_init);
512