summaryrefslogtreecommitdiff
path: root/drivers/clocksource/cadence_ttc_timer.c
blob: 63f176de0d0228c63ba58f606d21afd98cdc5e9e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
/*
 * This file contains driver for the Cadence Triple Timer Counter Rev 06
 *
 *  Copyright (C) 2011-2013 Xilinx
 *
 * based on arch/mips/kernel/time.c timer driver
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/clk.h>
#include <linux/interrupt.h>
#include <linux/clockchips.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/slab.h>
#include <linux/sched_clock.h>

/*
 * This driver configures the 2 16-bit count-up timers as follows:
 *
 * T1: Timer 1, clocksource for generic timekeeping
 * T2: Timer 2, clockevent source for hrtimers
 * T3: Timer 3, <unused>
 *
 * The input frequency to the timer module for emulation is 2.5MHz which is
 * common to all the timer channels (T1, T2, and T3). With a pre-scaler of 32,
 * the timers are clocked at 78.125KHz (12.8 us resolution).

 * The input frequency to the timer module in silicon is configurable and
 * obtained from device tree. The pre-scaler of 32 is used.
 */

/*
 * Timer Register Offset Definitions of Timer 1, Increment base address by 4
 * and use same offsets for Timer 2
 */
#define TTC_CLK_CNTRL_OFFSET		0x00 /* Clock Control Reg, RW */
#define TTC_CNT_CNTRL_OFFSET		0x0C /* Counter Control Reg, RW */
#define TTC_COUNT_VAL_OFFSET		0x18 /* Counter Value Reg, RO */
#define TTC_INTR_VAL_OFFSET		0x24 /* Interval Count Reg, RW */
#define TTC_ISR_OFFSET		0x54 /* Interrupt Status Reg, RO */
#define TTC_IER_OFFSET		0x60 /* Interrupt Enable Reg, RW */

#define TTC_CNT_CNTRL_DISABLE_MASK	0x1

#define TTC_CLK_CNTRL_CSRC_MASK		(1 << 5)	/* clock source */

/*
 * Setup the timers to use pre-scaling, using a fixed value for now that will
 * work across most input frequency, but it may need to be more dynamic
 */
#define PRESCALE_EXPONENT	11	/* 2 ^ PRESCALE_EXPONENT = PRESCALE */
#define PRESCALE		2048	/* The exponent must match this */
#define CLK_CNTRL_PRESCALE	((PRESCALE_EXPONENT - 1) << 1)
#define CLK_CNTRL_PRESCALE_EN	1
#define CNT_CNTRL_RESET		(1 << 4)

/**
 * struct ttc_timer - This definition defines local timer structure
 *
 * @base_addr:	Base address of timer
 * @freq:	Timer input clock frequency
 * @clk:	Associated clock source
 * @clk_rate_change_nb	Notifier block for clock rate changes
 */
struct ttc_timer {
	void __iomem *base_addr;
	unsigned long freq;
	struct clk *clk;
	struct notifier_block clk_rate_change_nb;
};

#define to_ttc_timer(x) \
		container_of(x, struct ttc_timer, clk_rate_change_nb)

struct ttc_timer_clocksource {
	struct ttc_timer	ttc;
	struct clocksource	cs;
};

#define to_ttc_timer_clksrc(x) \
		container_of(x, struct ttc_timer_clocksource, cs)

struct ttc_timer_clockevent {
	struct ttc_timer		ttc;
	struct clock_event_device	ce;
};

#define to_ttc_timer_clkevent(x) \
		container_of(x, struct ttc_timer_clockevent, ce)

static void __iomem *ttc_sched_clock_val_reg;

/**
 * ttc_set_interval - Set the timer interval value
 *
 * @timer:	Pointer to the timer instance
 * @cycles:	Timer interval ticks
 **/
static void ttc_set_interval(struct ttc_timer *timer,
					unsigned long cycles)
{
	u32 ctrl_reg;

	/* Disable the counter, set the counter value  and re-enable counter */
	ctrl_reg = __raw_readl(timer->base_addr + TTC_CNT_CNTRL_OFFSET);
	ctrl_reg |= TTC_CNT_CNTRL_DISABLE_MASK;
	__raw_writel(ctrl_reg, timer->base_addr + TTC_CNT_CNTRL_OFFSET);

	__raw_writel(cycles, timer->base_addr + TTC_INTR_VAL_OFFSET);

	/*
	 * Reset the counter (0x10) so that it starts from 0, one-shot
	 * mode makes this needed for timing to be right.
	 */
	ctrl_reg |= CNT_CNTRL_RESET;
	ctrl_reg &= ~TTC_CNT_CNTRL_DISABLE_MASK;
	__raw_writel(ctrl_reg, timer->base_addr + TTC_CNT_CNTRL_OFFSET);
}

/**
 * ttc_clock_event_interrupt - Clock event timer interrupt handler
 *
 * @irq:	IRQ number of the Timer
 * @dev_id:	void pointer to the ttc_timer instance
 *
 * returns: Always IRQ_HANDLED - success
 **/
static irqreturn_t ttc_clock_event_interrupt(int irq, void *dev_id)
{
	struct ttc_timer_clockevent *ttce = dev_id;
	struct ttc_timer *timer = &ttce->ttc;

	/* Acknowledge the interrupt and call event handler */
	__raw_readl(timer->base_addr + TTC_ISR_OFFSET);

	ttce->ce.event_handler(&ttce->ce);

	return IRQ_HANDLED;
}

/**
 * __ttc_clocksource_read - Reads the timer counter register
 *
 * returns: Current timer counter register value
 **/
static cycle_t __ttc_clocksource_read(struct clocksource *cs)
{
	struct ttc_timer *timer = &to_ttc_timer_clksrc(cs)->ttc;

	return (cycle_t)__raw_readl(timer->base_addr +
				TTC_COUNT_VAL_OFFSET);
}

static u64 notrace ttc_sched_clock_read(void)
{
	return __raw_readl(ttc_sched_clock_val_reg);
}

/**
 * ttc_set_next_event - Sets the time interval for next event
 *
 * @cycles:	Timer interval ticks
 * @evt:	Address of clock event instance
 *
 * returns: Always 0 - success
 **/
static int ttc_set_next_event(unsigned long cycles,
					struct clock_event_device *evt)
{
	struct ttc_timer_clockevent *ttce = to_ttc_timer_clkevent(evt);
	struct ttc_timer *timer = &ttce->ttc;

	ttc_set_interval(timer, cycles);
	return 0;
}

/**
 * ttc_set_mode - Sets the mode of timer
 *
 * @mode:	Mode to be set
 * @evt:	Address of clock event instance
 **/
static void ttc_set_mode(enum clock_event_mode mode,
					struct clock_event_device *evt)
{
	struct ttc_timer_clockevent *ttce = to_ttc_timer_clkevent(evt);
	struct ttc_timer *timer = &ttce->ttc;
	u32 ctrl_reg;

	switch (mode) {
	case CLOCK_EVT_MODE_PERIODIC:
		ttc_set_interval(timer, DIV_ROUND_CLOSEST(ttce->ttc.freq,
						PRESCALE * HZ));
		break;
	case CLOCK_EVT_MODE_ONESHOT:
	case CLOCK_EVT_MODE_UNUSED:
	case CLOCK_EVT_MODE_SHUTDOWN:
		ctrl_reg = __raw_readl(timer->base_addr +
					TTC_CNT_CNTRL_OFFSET);
		ctrl_reg |= TTC_CNT_CNTRL_DISABLE_MASK;
		__raw_writel(ctrl_reg,
				timer->base_addr + TTC_CNT_CNTRL_OFFSET);
		break;
	case CLOCK_EVT_MODE_RESUME:
		ctrl_reg = __raw_readl(timer->base_addr +
					TTC_CNT_CNTRL_OFFSET);
		ctrl_reg &= ~TTC_CNT_CNTRL_DISABLE_MASK;
		__raw_writel(ctrl_reg,
				timer->base_addr + TTC_CNT_CNTRL_OFFSET);
		break;
	}
}

static int ttc_rate_change_clocksource_cb(struct notifier_block *nb,
		unsigned long event, void *data)
{
	struct clk_notifier_data *ndata = data;
	struct ttc_timer *ttc = to_ttc_timer(nb);
	struct ttc_timer_clocksource *ttccs = container_of(ttc,
			struct ttc_timer_clocksource, ttc);

	switch (event) {
	case POST_RATE_CHANGE:
		/*
		 * Do whatever is necessary to maintain a proper time base
		 *
		 * I cannot find a way to adjust the currently used clocksource
		 * to the new frequency. __clocksource_updatefreq_hz() sounds
		 * good, but does not work. Not sure what's that missing.
		 *
		 * This approach works, but triggers two clocksource switches.
		 * The first after unregister to clocksource jiffies. And
		 * another one after the register to the newly registered timer.
		 *
		 * Alternatively we could 'waste' another HW timer to ping pong
		 * between clock sources. That would also use one register and
		 * one unregister call, but only trigger one clocksource switch
		 * for the cost of another HW timer used by the OS.
		 */
		clocksource_unregister(&ttccs->cs);
		clocksource_register_hz(&ttccs->cs,
				ndata->new_rate / PRESCALE);
		/* fall through */
	case PRE_RATE_CHANGE:
	case ABORT_RATE_CHANGE:
	default:
		return NOTIFY_DONE;
	}
}

static void __init ttc_setup_clocksource(struct clk *clk, void __iomem *base)
{
	struct ttc_timer_clocksource *ttccs;
	int err;

	ttccs = kzalloc(sizeof(*ttccs), GFP_KERNEL);
	if (WARN_ON(!ttccs))
		return;

	ttccs->ttc.clk = clk;

	err = clk_prepare_enable(ttccs->ttc.clk);
	if (WARN_ON(err)) {
		kfree(ttccs);
		return;
	}

	ttccs->ttc.freq = clk_get_rate(ttccs->ttc.clk);

	ttccs->ttc.clk_rate_change_nb.notifier_call =
		ttc_rate_change_clocksource_cb;
	ttccs->ttc.clk_rate_change_nb.next = NULL;
	if (clk_notifier_register(ttccs->ttc.clk,
				&ttccs->ttc.clk_rate_change_nb))
		pr_warn("Unable to register clock notifier.\n");

	ttccs->ttc.base_addr = base;
	ttccs->cs.name = "ttc_clocksource";
	ttccs->cs.rating = 200;
	ttccs->cs.read = __ttc_clocksource_read;
	ttccs->cs.mask = CLOCKSOURCE_MASK(16);
	ttccs->cs.flags = CLOCK_SOURCE_IS_CONTINUOUS;

	/*
	 * Setup the clock source counter to be an incrementing counter
	 * with no interrupt and it rolls over at 0xFFFF. Pre-scale
	 * it by 32 also. Let it start running now.
	 */
	__raw_writel(0x0,  ttccs->ttc.base_addr + TTC_IER_OFFSET);
	__raw_writel(CLK_CNTRL_PRESCALE | CLK_CNTRL_PRESCALE_EN,
		     ttccs->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
	__raw_writel(CNT_CNTRL_RESET,
		     ttccs->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);

	err = clocksource_register_hz(&ttccs->cs, ttccs->ttc.freq / PRESCALE);
	if (WARN_ON(err)) {
		kfree(ttccs);
		return;
	}

	ttc_sched_clock_val_reg = base + TTC_COUNT_VAL_OFFSET;
	sched_clock_register(ttc_sched_clock_read, 16, ttccs->ttc.freq / PRESCALE);
}

static int ttc_rate_change_clockevent_cb(struct notifier_block *nb,
		unsigned long event, void *data)
{
	struct clk_notifier_data *ndata = data;
	struct ttc_timer *ttc = to_ttc_timer(nb);
	struct ttc_timer_clockevent *ttcce = container_of(ttc,
			struct ttc_timer_clockevent, ttc);

	switch (event) {
	case POST_RATE_CHANGE:
	{
		unsigned long flags;

		/*
		 * clockevents_update_freq should be called with IRQ disabled on
		 * the CPU the timer provides events for. The timer we use is
		 * common to both CPUs, not sure if we need to run on both
		 * cores.
		 */
		local_irq_save(flags);
		clockevents_update_freq(&ttcce->ce,
				ndata->new_rate / PRESCALE);
		local_irq_restore(flags);

		/* update cached frequency */
		ttc->freq = ndata->new_rate;

		/* fall through */
	}
	case PRE_RATE_CHANGE:
	case ABORT_RATE_CHANGE:
	default:
		return NOTIFY_DONE;
	}
}

static void __init ttc_setup_clockevent(struct clk *clk,
						void __iomem *base, u32 irq)
{
	struct ttc_timer_clockevent *ttcce;
	int err;

	ttcce = kzalloc(sizeof(*ttcce), GFP_KERNEL);
	if (WARN_ON(!ttcce))
		return;

	ttcce->ttc.clk = clk;

	err = clk_prepare_enable(ttcce->ttc.clk);
	if (WARN_ON(err)) {
		kfree(ttcce);
		return;
	}

	ttcce->ttc.clk_rate_change_nb.notifier_call =
		ttc_rate_change_clockevent_cb;
	ttcce->ttc.clk_rate_change_nb.next = NULL;
	if (clk_notifier_register(ttcce->ttc.clk,
				&ttcce->ttc.clk_rate_change_nb))
		pr_warn("Unable to register clock notifier.\n");
	ttcce->ttc.freq = clk_get_rate(ttcce->ttc.clk);

	ttcce->ttc.base_addr = base;
	ttcce->ce.name = "ttc_clockevent";
	ttcce->ce.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
	ttcce->ce.set_next_event = ttc_set_next_event;
	ttcce->ce.set_mode = ttc_set_mode;
	ttcce->ce.rating = 200;
	ttcce->ce.irq = irq;
	ttcce->ce.cpumask = cpu_possible_mask;

	/*
	 * Setup the clock event timer to be an interval timer which
	 * is prescaled by 32 using the interval interrupt. Leave it
	 * disabled for now.
	 */
	__raw_writel(0x23, ttcce->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);
	__raw_writel(CLK_CNTRL_PRESCALE | CLK_CNTRL_PRESCALE_EN,
		     ttcce->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
	__raw_writel(0x1,  ttcce->ttc.base_addr + TTC_IER_OFFSET);

	err = request_irq(irq, ttc_clock_event_interrupt,
			  IRQF_TIMER, ttcce->ce.name, ttcce);
	if (WARN_ON(err)) {
		kfree(ttcce);
		return;
	}

	clockevents_config_and_register(&ttcce->ce,
			ttcce->ttc.freq / PRESCALE, 1, 0xfffe);
}

/**
 * ttc_timer_init - Initialize the timer
 *
 * Initializes the timer hardware and register the clock source and clock event
 * timers with Linux kernal timer framework
 */
static void __init ttc_timer_init(struct device_node *timer)
{
	unsigned int irq;
	void __iomem *timer_baseaddr;
	struct clk *clk_cs, *clk_ce;
	static int initialized;
	int clksel;

	if (initialized)
		return;

	initialized = 1;

	/*
	 * Get the 1st Triple Timer Counter (TTC) block from the device tree
	 * and use it. Note that the event timer uses the interrupt and it's the
	 * 2nd TTC hence the irq_of_parse_and_map(,1)
	 */
	timer_baseaddr = of_iomap(timer, 0);
	if (!timer_baseaddr) {
		pr_err("ERROR: invalid timer base address\n");
		BUG();
	}

	irq = irq_of_parse_and_map(timer, 1);
	if (irq <= 0) {
		pr_err("ERROR: invalid interrupt number\n");
		BUG();
	}

	clksel = __raw_readl(timer_baseaddr + TTC_CLK_CNTRL_OFFSET);
	clksel = !!(clksel & TTC_CLK_CNTRL_CSRC_MASK);
	clk_cs = of_clk_get(timer, clksel);
	if (IS_ERR(clk_cs)) {
		pr_err("ERROR: timer input clock not found\n");
		BUG();
	}

	clksel = __raw_readl(timer_baseaddr + 4 + TTC_CLK_CNTRL_OFFSET);
	clksel = !!(clksel & TTC_CLK_CNTRL_CSRC_MASK);
	clk_ce = of_clk_get(timer, clksel);
	if (IS_ERR(clk_ce)) {
		pr_err("ERROR: timer input clock not found\n");
		BUG();
	}

	ttc_setup_clocksource(clk_cs, timer_baseaddr);
	ttc_setup_clockevent(clk_ce, timer_baseaddr + 4, irq);

	pr_info("%s #0 at %p, irq=%d\n", timer->name, timer_baseaddr, irq);
}

CLOCKSOURCE_OF_DECLARE(ttc, "cdns,ttc", ttc_timer_init);