1// SPDX-License-Identifier: GPL-2.0
2/*
3 * 64-bit Periodic Interval Timer driver
4 *
5 * Copyright (C) 2019 Microchip Technology Inc. and its subsidiaries
6 *
7 * Author: Claudiu Beznea <claudiu.beznea@microchip.com>
8 */
9
10#include <linux/clk.h>
11#include <linux/clockchips.h>
12#include <linux/delay.h>
13#include <linux/interrupt.h>
14#include <linux/of_address.h>
15#include <linux/of_irq.h>
16#include <linux/sched_clock.h>
17#include <linux/slab.h>
18
19#define MCHP_PIT64B_CR 0x00 /* Control Register */
20#define MCHP_PIT64B_CR_START BIT(0)
21#define MCHP_PIT64B_CR_SWRST BIT(8)
22
23#define MCHP_PIT64B_MR 0x04 /* Mode Register */
24#define MCHP_PIT64B_MR_CONT BIT(0)
25#define MCHP_PIT64B_MR_ONE_SHOT (0)
26#define MCHP_PIT64B_MR_SGCLK BIT(3)
27#define MCHP_PIT64B_MR_PRES GENMASK(11, 8)
28
29#define MCHP_PIT64B_LSB_PR 0x08 /* LSB Period Register */
30
31#define MCHP_PIT64B_MSB_PR 0x0C /* MSB Period Register */
32
33#define MCHP_PIT64B_IER 0x10 /* Interrupt Enable Register */
34#define MCHP_PIT64B_IER_PERIOD BIT(0)
35
36#define MCHP_PIT64B_ISR 0x1C /* Interrupt Status Register */
37
38#define MCHP_PIT64B_TLSBR 0x20 /* Timer LSB Register */
39
40#define MCHP_PIT64B_TMSBR 0x24 /* Timer MSB Register */
41
42#define MCHP_PIT64B_PRES_MAX 0x10
43#define MCHP_PIT64B_LSBMASK GENMASK_ULL(31, 0)
44#define MCHP_PIT64B_PRES_TO_MODE(p) (MCHP_PIT64B_MR_PRES & ((p) << 8))
45#define MCHP_PIT64B_MODE_TO_PRES(m) ((MCHP_PIT64B_MR_PRES & (m)) >> 8)
46#define MCHP_PIT64B_DEF_FREQ 5000000UL /* 5 MHz */
47
48#define MCHP_PIT64B_NAME "pit64b"
49
50/**
51 * struct mchp_pit64b_timer - PIT64B timer data structure
52 * @base: base address of PIT64B hardware block
53 * @pclk: PIT64B's peripheral clock
54 * @gclk: PIT64B's generic clock
55 * @mode: precomputed value for mode register
56 */
57struct mchp_pit64b_timer {
58 void __iomem *base;
59 struct clk *pclk;
60 struct clk *gclk;
61 u32 mode;
62};
63
64/**
65 * struct mchp_pit64b_clkevt - PIT64B clockevent data structure
66 * @timer: PIT64B timer
67 * @clkevt: clockevent
68 */
69struct mchp_pit64b_clkevt {
70 struct mchp_pit64b_timer timer;
71 struct clock_event_device clkevt;
72};
73
74#define clkevt_to_mchp_pit64b_timer(x) \
75 ((struct mchp_pit64b_timer *)container_of(x,\
76 struct mchp_pit64b_clkevt, clkevt))
77
78/**
79 * struct mchp_pit64b_clksrc - PIT64B clocksource data structure
80 * @timer: PIT64B timer
81 * @clksrc: clocksource
82 */
83struct mchp_pit64b_clksrc {
84 struct mchp_pit64b_timer timer;
85 struct clocksource clksrc;
86};
87
88#define clksrc_to_mchp_pit64b_timer(x) \
89 ((struct mchp_pit64b_timer *)container_of(x,\
90 struct mchp_pit64b_clksrc, clksrc))
91
92/* Base address for clocksource timer. */
93static void __iomem *mchp_pit64b_cs_base;
94/* Default cycles for clockevent timer. */
95static u64 mchp_pit64b_ce_cycles;
96/* Delay timer. */
97static struct delay_timer mchp_pit64b_dt;
98
99static inline u64 mchp_pit64b_cnt_read(void __iomem *base)
100{
101 unsigned long flags;
102 u32 low, high;
103
104 raw_local_irq_save(flags);
105
106 /*
107 * When using a 64 bit period TLSB must be read first, followed by the
108 * read of TMSB. This sequence generates an atomic read of the 64 bit
109 * timer value whatever the lapse of time between the accesses.
110 */
111 low = readl_relaxed(base + MCHP_PIT64B_TLSBR);
112 high = readl_relaxed(base + MCHP_PIT64B_TMSBR);
113
114 raw_local_irq_restore(flags);
115
116 return (((u64)high << 32) | low);
117}
118
119static inline void mchp_pit64b_reset(struct mchp_pit64b_timer *timer,
120 u64 cycles, u32 mode, u32 irqs)
121{
122 u32 low, high;
123
124 low = cycles & MCHP_PIT64B_LSBMASK;
125 high = cycles >> 32;
126
127 writel_relaxed(MCHP_PIT64B_CR_SWRST, timer->base + MCHP_PIT64B_CR);
128 writel_relaxed(mode | timer->mode, timer->base + MCHP_PIT64B_MR);
129 writel_relaxed(high, timer->base + MCHP_PIT64B_MSB_PR);
130 writel_relaxed(low, timer->base + MCHP_PIT64B_LSB_PR);
131 writel_relaxed(irqs, timer->base + MCHP_PIT64B_IER);
132 writel_relaxed(MCHP_PIT64B_CR_START, timer->base + MCHP_PIT64B_CR);
133}
134
135static void mchp_pit64b_suspend(struct mchp_pit64b_timer *timer)
136{
137 writel_relaxed(MCHP_PIT64B_CR_SWRST, timer->base + MCHP_PIT64B_CR);
138 if (timer->mode & MCHP_PIT64B_MR_SGCLK)
139 clk_disable_unprepare(clk: timer->gclk);
140 clk_disable_unprepare(clk: timer->pclk);
141}
142
143static void mchp_pit64b_resume(struct mchp_pit64b_timer *timer)
144{
145 clk_prepare_enable(clk: timer->pclk);
146 if (timer->mode & MCHP_PIT64B_MR_SGCLK)
147 clk_prepare_enable(clk: timer->gclk);
148}
149
150static void mchp_pit64b_clksrc_suspend(struct clocksource *cs)
151{
152 struct mchp_pit64b_timer *timer = clksrc_to_mchp_pit64b_timer(cs);
153
154 mchp_pit64b_suspend(timer);
155}
156
157static void mchp_pit64b_clksrc_resume(struct clocksource *cs)
158{
159 struct mchp_pit64b_timer *timer = clksrc_to_mchp_pit64b_timer(cs);
160
161 mchp_pit64b_resume(timer);
162 mchp_pit64b_reset(timer, ULLONG_MAX, MCHP_PIT64B_MR_CONT, irqs: 0);
163}
164
165static u64 mchp_pit64b_clksrc_read(struct clocksource *cs)
166{
167 return mchp_pit64b_cnt_read(base: mchp_pit64b_cs_base);
168}
169
170static u64 notrace mchp_pit64b_sched_read_clk(void)
171{
172 return mchp_pit64b_cnt_read(base: mchp_pit64b_cs_base);
173}
174
175static unsigned long notrace mchp_pit64b_dt_read(void)
176{
177 return mchp_pit64b_cnt_read(base: mchp_pit64b_cs_base);
178}
179
180static int mchp_pit64b_clkevt_shutdown(struct clock_event_device *cedev)
181{
182 struct mchp_pit64b_timer *timer = clkevt_to_mchp_pit64b_timer(cedev);
183
184 if (!clockevent_state_detached(dev: cedev))
185 mchp_pit64b_suspend(timer);
186
187 return 0;
188}
189
190static int mchp_pit64b_clkevt_set_periodic(struct clock_event_device *cedev)
191{
192 struct mchp_pit64b_timer *timer = clkevt_to_mchp_pit64b_timer(cedev);
193
194 if (clockevent_state_shutdown(dev: cedev))
195 mchp_pit64b_resume(timer);
196
197 mchp_pit64b_reset(timer, cycles: mchp_pit64b_ce_cycles, MCHP_PIT64B_MR_CONT,
198 MCHP_PIT64B_IER_PERIOD);
199
200 return 0;
201}
202
203static int mchp_pit64b_clkevt_set_oneshot(struct clock_event_device *cedev)
204{
205 struct mchp_pit64b_timer *timer = clkevt_to_mchp_pit64b_timer(cedev);
206
207 if (clockevent_state_shutdown(dev: cedev))
208 mchp_pit64b_resume(timer);
209
210 mchp_pit64b_reset(timer, cycles: mchp_pit64b_ce_cycles, MCHP_PIT64B_MR_ONE_SHOT,
211 MCHP_PIT64B_IER_PERIOD);
212
213 return 0;
214}
215
216static int mchp_pit64b_clkevt_set_next_event(unsigned long evt,
217 struct clock_event_device *cedev)
218{
219 struct mchp_pit64b_timer *timer = clkevt_to_mchp_pit64b_timer(cedev);
220
221 mchp_pit64b_reset(timer, cycles: evt, MCHP_PIT64B_MR_ONE_SHOT,
222 MCHP_PIT64B_IER_PERIOD);
223
224 return 0;
225}
226
227static irqreturn_t mchp_pit64b_interrupt(int irq, void *dev_id)
228{
229 struct mchp_pit64b_clkevt *irq_data = dev_id;
230
231 /* Need to clear the interrupt. */
232 readl_relaxed(irq_data->timer.base + MCHP_PIT64B_ISR);
233
234 irq_data->clkevt.event_handler(&irq_data->clkevt);
235
236 return IRQ_HANDLED;
237}
238
239static void __init mchp_pit64b_pres_compute(u32 *pres, u32 clk_rate,
240 u32 max_rate)
241{
242 u32 tmp;
243
244 for (*pres = 0; *pres < MCHP_PIT64B_PRES_MAX; (*pres)++) {
245 tmp = clk_rate / (*pres + 1);
246 if (tmp <= max_rate)
247 break;
248 }
249
250 /* Use the biggest prescaler if we didn't match one. */
251 if (*pres == MCHP_PIT64B_PRES_MAX)
252 *pres = MCHP_PIT64B_PRES_MAX - 1;
253}
254
255/**
256 * mchp_pit64b_init_mode() - prepare PIT64B mode register value to be used at
257 * runtime; this includes prescaler and SGCLK bit
258 * @timer: pointer to pit64b timer to init
259 * @max_rate: maximum rate that timer's clock could use
260 *
261 * PIT64B timer may be fed by gclk or pclk. When gclk is used its rate has to
262 * be at least 3 times lower that pclk's rate. pclk rate is fixed, gclk rate
263 * could be changed via clock APIs. The chosen clock (pclk or gclk) could be
264 * divided by the internal PIT64B's divider.
265 *
266 * This function, first tries to use GCLK by requesting the desired rate from
267 * PMC and then using the internal PIT64B prescaler, if any, to reach the
268 * requested rate. If PCLK/GCLK < 3 (condition requested by PIT64B hardware)
269 * then the function falls back on using PCLK as clock source for PIT64B timer
270 * choosing the highest prescaler in case it doesn't locate one to match the
271 * requested frequency.
272 *
273 * Below is presented the PIT64B block in relation with PMC:
274 *
275 * PIT64B
276 * PMC +------------------------------------+
277 * +----+ | +-----+ |
278 * | |-->gclk -->|-->| | +---------+ +-----+ |
279 * | | | | MUX |--->| Divider |->|timer| |
280 * | |-->pclk -->|-->| | +---------+ +-----+ |
281 * +----+ | +-----+ |
282 * | ^ |
283 * | sel |
284 * +------------------------------------+
285 *
286 * Where:
287 * - gclk rate <= pclk rate/3
288 * - gclk rate could be requested from PMC
289 * - pclk rate is fixed (cannot be requested from PMC)
290 */
291static int __init mchp_pit64b_init_mode(struct mchp_pit64b_timer *timer,
292 unsigned long max_rate)
293{
294 unsigned long pclk_rate, diff = 0, best_diff = ULONG_MAX;
295 long gclk_round = 0;
296 u32 pres, best_pres = 0;
297
298 pclk_rate = clk_get_rate(clk: timer->pclk);
299 if (!pclk_rate)
300 return -EINVAL;
301
302 timer->mode = 0;
303
304 /* Try using GCLK. */
305 gclk_round = clk_round_rate(clk: timer->gclk, rate: max_rate);
306 if (gclk_round < 0)
307 goto pclk;
308
309 if (pclk_rate / gclk_round < 3)
310 goto pclk;
311
312 mchp_pit64b_pres_compute(pres: &pres, clk_rate: gclk_round, max_rate);
313 best_diff = abs(gclk_round / (pres + 1) - max_rate);
314 best_pres = pres;
315
316 if (!best_diff) {
317 timer->mode |= MCHP_PIT64B_MR_SGCLK;
318 clk_set_rate(clk: timer->gclk, rate: gclk_round);
319 goto done;
320 }
321
322pclk:
323 /* Check if requested rate could be obtained using PCLK. */
324 mchp_pit64b_pres_compute(pres: &pres, clk_rate: pclk_rate, max_rate);
325 diff = abs(pclk_rate / (pres + 1) - max_rate);
326
327 if (best_diff > diff) {
328 /* Use PCLK. */
329 best_pres = pres;
330 } else {
331 /* Use GCLK. */
332 timer->mode |= MCHP_PIT64B_MR_SGCLK;
333 clk_set_rate(clk: timer->gclk, rate: gclk_round);
334 }
335
336done:
337 timer->mode |= MCHP_PIT64B_PRES_TO_MODE(best_pres);
338
339 pr_info("PIT64B: using clk=%s with prescaler %u, freq=%lu [Hz]\n",
340 timer->mode & MCHP_PIT64B_MR_SGCLK ? "gclk" : "pclk", best_pres,
341 timer->mode & MCHP_PIT64B_MR_SGCLK ?
342 gclk_round / (best_pres + 1) : pclk_rate / (best_pres + 1));
343
344 return 0;
345}
346
347static int __init mchp_pit64b_init_clksrc(struct mchp_pit64b_timer *timer,
348 u32 clk_rate)
349{
350 struct mchp_pit64b_clksrc *cs;
351 int ret;
352
353 cs = kzalloc(sizeof(*cs), GFP_KERNEL);
354 if (!cs)
355 return -ENOMEM;
356
357 mchp_pit64b_resume(timer);
358 mchp_pit64b_reset(timer, ULLONG_MAX, MCHP_PIT64B_MR_CONT, irqs: 0);
359
360 mchp_pit64b_cs_base = timer->base;
361
362 cs->timer.base = timer->base;
363 cs->timer.pclk = timer->pclk;
364 cs->timer.gclk = timer->gclk;
365 cs->timer.mode = timer->mode;
366 cs->clksrc.name = MCHP_PIT64B_NAME;
367 cs->clksrc.mask = CLOCKSOURCE_MASK(64);
368 cs->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
369 cs->clksrc.rating = 210;
370 cs->clksrc.read = mchp_pit64b_clksrc_read;
371 cs->clksrc.suspend = mchp_pit64b_clksrc_suspend;
372 cs->clksrc.resume = mchp_pit64b_clksrc_resume;
373
374 ret = clocksource_register_hz(cs: &cs->clksrc, hz: clk_rate);
375 if (ret) {
376 pr_debug("clksrc: Failed to register PIT64B clocksource!\n");
377
378 /* Stop timer. */
379 mchp_pit64b_suspend(timer);
380 kfree(objp: cs);
381
382 return ret;
383 }
384
385 sched_clock_register(read: mchp_pit64b_sched_read_clk, bits: 64, rate: clk_rate);
386
387 mchp_pit64b_dt.read_current_timer = mchp_pit64b_dt_read;
388 mchp_pit64b_dt.freq = clk_rate;
389 register_current_timer_delay(&mchp_pit64b_dt);
390
391 return 0;
392}
393
394static int __init mchp_pit64b_init_clkevt(struct mchp_pit64b_timer *timer,
395 u32 clk_rate, u32 irq)
396{
397 struct mchp_pit64b_clkevt *ce;
398 int ret;
399
400 ce = kzalloc(sizeof(*ce), GFP_KERNEL);
401 if (!ce)
402 return -ENOMEM;
403
404 mchp_pit64b_ce_cycles = DIV_ROUND_CLOSEST(clk_rate, HZ);
405
406 ce->timer.base = timer->base;
407 ce->timer.pclk = timer->pclk;
408 ce->timer.gclk = timer->gclk;
409 ce->timer.mode = timer->mode;
410 ce->clkevt.name = MCHP_PIT64B_NAME;
411 ce->clkevt.features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC;
412 ce->clkevt.rating = 150;
413 ce->clkevt.set_state_shutdown = mchp_pit64b_clkevt_shutdown;
414 ce->clkevt.set_state_periodic = mchp_pit64b_clkevt_set_periodic;
415 ce->clkevt.set_state_oneshot = mchp_pit64b_clkevt_set_oneshot;
416 ce->clkevt.set_next_event = mchp_pit64b_clkevt_set_next_event;
417 ce->clkevt.cpumask = cpumask_of(0);
418 ce->clkevt.irq = irq;
419
420 ret = request_irq(irq, handler: mchp_pit64b_interrupt, IRQF_TIMER,
421 name: "pit64b_tick", dev: ce);
422 if (ret) {
423 pr_debug("clkevt: Failed to setup PIT64B IRQ\n");
424 kfree(objp: ce);
425 return ret;
426 }
427
428 clockevents_config_and_register(dev: &ce->clkevt, freq: clk_rate, min_delta: 1, ULONG_MAX);
429
430 return 0;
431}
432
433static int __init mchp_pit64b_dt_init_timer(struct device_node *node,
434 bool clkevt)
435{
436 struct mchp_pit64b_timer timer;
437 unsigned long clk_rate;
438 u32 irq = 0;
439 int ret;
440
441 /* Parse DT node. */
442 timer.pclk = of_clk_get_by_name(np: node, name: "pclk");
443 if (IS_ERR(ptr: timer.pclk))
444 return PTR_ERR(ptr: timer.pclk);
445
446 timer.gclk = of_clk_get_by_name(np: node, name: "gclk");
447 if (IS_ERR(ptr: timer.gclk))
448 return PTR_ERR(ptr: timer.gclk);
449
450 timer.base = of_iomap(node, index: 0);
451 if (!timer.base)
452 return -ENXIO;
453
454 if (clkevt) {
455 irq = irq_of_parse_and_map(node, index: 0);
456 if (!irq) {
457 ret = -ENODEV;
458 goto io_unmap;
459 }
460 }
461
462 /* Initialize mode (prescaler + SGCK bit). To be used at runtime. */
463 ret = mchp_pit64b_init_mode(timer: &timer, MCHP_PIT64B_DEF_FREQ);
464 if (ret)
465 goto irq_unmap;
466
467 if (timer.mode & MCHP_PIT64B_MR_SGCLK)
468 clk_rate = clk_get_rate(clk: timer.gclk);
469 else
470 clk_rate = clk_get_rate(clk: timer.pclk);
471 clk_rate = clk_rate / (MCHP_PIT64B_MODE_TO_PRES(timer.mode) + 1);
472
473 if (clkevt)
474 ret = mchp_pit64b_init_clkevt(timer: &timer, clk_rate, irq);
475 else
476 ret = mchp_pit64b_init_clksrc(timer: &timer, clk_rate);
477
478 if (ret)
479 goto irq_unmap;
480
481 return 0;
482
483irq_unmap:
484 irq_dispose_mapping(virq: irq);
485io_unmap:
486 iounmap(addr: timer.base);
487
488 return ret;
489}
490
491static int __init mchp_pit64b_dt_init(struct device_node *node)
492{
493 static int inits;
494
495 switch (inits++) {
496 case 0:
497 /* 1st request, register clockevent. */
498 return mchp_pit64b_dt_init_timer(node, clkevt: true);
499 case 1:
500 /* 2nd request, register clocksource. */
501 return mchp_pit64b_dt_init_timer(node, clkevt: false);
502 }
503
504 /* The rest, don't care. */
505 return -EINVAL;
506}
507
508TIMER_OF_DECLARE(mchp_pit64b, "microchip,sam9x60-pit64b", mchp_pit64b_dt_init);
509

source code of linux/drivers/clocksource/timer-microchip-pit64b.c