2 * at91sam926x_time.c - Periodic Interval Timer (PIT) for at91sam926x
4 * Copyright (C) 2005-2006 M. Amine SAYA, ATMEL Rousset, France
5 * Revision 2005 M. Nicolas Diremdjian, ATMEL Rousset, France
6 * Converted to ClockSource/ClockEvents by David Brownell.
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
13 #define pr_fmt(fmt) "AT91: PIT: " fmt
15 #include <linux/clk.h>
16 #include <linux/clockchips.h>
17 #include <linux/interrupt.h>
18 #include <linux/irq.h>
19 #include <linux/kernel.h>
21 #include <linux/of_address.h>
22 #include <linux/of_irq.h>
23 #include <linux/slab.h>
25 #define AT91_PIT_MR 0x00 /* Mode Register */
26 #define AT91_PIT_PITIEN BIT(25) /* Timer Interrupt Enable */
27 #define AT91_PIT_PITEN BIT(24) /* Timer Enabled */
28 #define AT91_PIT_PIV GENMASK(19, 0) /* Periodic Interval Value */
30 #define AT91_PIT_SR 0x04 /* Status Register */
31 #define AT91_PIT_PITS BIT(0) /* Timer Status */
33 #define AT91_PIT_PIVR 0x08 /* Periodic Interval Value Register */
34 #define AT91_PIT_PIIR 0x0c /* Periodic Interval Image Register */
35 #define AT91_PIT_PICNT GENMASK(31, 20) /* Interval Counter */
36 #define AT91_PIT_CPIV GENMASK(19, 0) /* Inverval Value */
38 #define PIT_CPIV(x) ((x) & AT91_PIT_CPIV)
39 #define PIT_PICNT(x) (((x) & AT91_PIT_PICNT) >> 20)
42 struct clock_event_device clkevt;
43 struct clocksource clksrc;
52 static inline struct pit_data *clksrc_to_pit_data(struct clocksource *clksrc)
54 return container_of(clksrc, struct pit_data, clksrc);
57 static inline struct pit_data *clkevt_to_pit_data(struct clock_event_device *clkevt)
59 return container_of(clkevt, struct pit_data, clkevt);
62 static inline unsigned int pit_read(void __iomem *base, unsigned int reg_offset)
64 return readl_relaxed(base + reg_offset);
67 static inline void pit_write(void __iomem *base, unsigned int reg_offset, unsigned long value)
69 writel_relaxed(value, base + reg_offset);
73 * Clocksource: just a monotonic counter of MCK/16 cycles.
74 * We don't care whether or not PIT irqs are enabled.
76 static cycle_t read_pit_clk(struct clocksource *cs)
78 struct pit_data *data = clksrc_to_pit_data(cs);
83 raw_local_irq_save(flags);
85 t = pit_read(data->base, AT91_PIT_PIIR);
86 raw_local_irq_restore(flags);
88 elapsed += PIT_PICNT(t) * data->cycle;
89 elapsed += PIT_CPIV(t);
93 static int pit_clkevt_shutdown(struct clock_event_device *dev)
95 struct pit_data *data = clkevt_to_pit_data(dev);
97 /* disable irq, leaving the clocksource active */
98 pit_write(data->base, AT91_PIT_MR, (data->cycle - 1) | AT91_PIT_PITEN);
103 * Clockevent device: interrupts every 1/HZ (== pit_cycles * MCK/16)
105 static int pit_clkevt_set_periodic(struct clock_event_device *dev)
107 struct pit_data *data = clkevt_to_pit_data(dev);
109 /* update clocksource counter */
110 data->cnt += data->cycle * PIT_PICNT(pit_read(data->base, AT91_PIT_PIVR));
111 pit_write(data->base, AT91_PIT_MR,
112 (data->cycle - 1) | AT91_PIT_PITEN | AT91_PIT_PITIEN);
116 static void at91sam926x_pit_suspend(struct clock_event_device *cedev)
118 struct pit_data *data = clkevt_to_pit_data(cedev);
121 pit_write(data->base, AT91_PIT_MR, 0);
124 static void at91sam926x_pit_reset(struct pit_data *data)
126 /* Disable timer and irqs */
127 pit_write(data->base, AT91_PIT_MR, 0);
129 /* Clear any pending interrupts, wait for PIT to stop counting */
130 while (PIT_CPIV(pit_read(data->base, AT91_PIT_PIVR)) != 0)
133 /* Start PIT but don't enable IRQ */
134 pit_write(data->base, AT91_PIT_MR,
135 (data->cycle - 1) | AT91_PIT_PITEN);
138 static void at91sam926x_pit_resume(struct clock_event_device *cedev)
140 struct pit_data *data = clkevt_to_pit_data(cedev);
142 at91sam926x_pit_reset(data);
146 * IRQ handler for the timer.
148 static irqreturn_t at91sam926x_pit_interrupt(int irq, void *dev_id)
150 struct pit_data *data = dev_id;
153 * irqs should be disabled here, but as the irq is shared they are only
154 * guaranteed to be off if the timer irq is registered first.
156 WARN_ON_ONCE(!irqs_disabled());
158 /* The PIT interrupt may be disabled, and is shared */
159 if (clockevent_state_periodic(&data->clkevt) &&
160 (pit_read(data->base, AT91_PIT_SR) & AT91_PIT_PITS)) {
163 /* Get number of ticks performed before irq, and ack it */
164 nr_ticks = PIT_PICNT(pit_read(data->base, AT91_PIT_PIVR));
166 data->cnt += data->cycle;
167 data->clkevt.event_handler(&data->clkevt);
178 * Set up both clocksource and clockevent support.
180 static int __init at91sam926x_pit_common_init(struct pit_data *data)
182 unsigned long pit_rate;
187 * Use our actual MCK to figure out how many MCK/16 ticks per
188 * 1/HZ period (instead of a compile-time constant LATCH).
190 pit_rate = clk_get_rate(data->mck) / 16;
191 data->cycle = DIV_ROUND_CLOSEST(pit_rate, HZ);
192 WARN_ON(((data->cycle - 1) & ~AT91_PIT_PIV) != 0);
194 /* Initialize and enable the timer */
195 at91sam926x_pit_reset(data);
198 * Register clocksource. The high order bits of PIV are unused,
199 * so this isn't a 32-bit counter unless we get clockevent irqs.
201 bits = 12 /* PICNT */ + ilog2(data->cycle) /* PIV */;
202 data->clksrc.mask = CLOCKSOURCE_MASK(bits);
203 data->clksrc.name = "pit";
204 data->clksrc.rating = 175;
205 data->clksrc.read = read_pit_clk;
206 data->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
208 ret = clocksource_register_hz(&data->clksrc, pit_rate);
210 pr_err("Failed to register clocksource");
214 /* Set up irq handler */
215 ret = request_irq(data->irq, at91sam926x_pit_interrupt,
216 IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
219 pr_err("Unable to setup IRQ\n");
223 /* Set up and register clockevents */
224 data->clkevt.name = "pit";
225 data->clkevt.features = CLOCK_EVT_FEAT_PERIODIC;
226 data->clkevt.shift = 32;
227 data->clkevt.mult = div_sc(pit_rate, NSEC_PER_SEC, data->clkevt.shift);
228 data->clkevt.rating = 100;
229 data->clkevt.cpumask = cpumask_of(0);
231 data->clkevt.set_state_shutdown = pit_clkevt_shutdown;
232 data->clkevt.set_state_periodic = pit_clkevt_set_periodic;
233 data->clkevt.resume = at91sam926x_pit_resume;
234 data->clkevt.suspend = at91sam926x_pit_suspend;
235 clockevents_register_device(&data->clkevt);
240 static int __init at91sam926x_pit_dt_init(struct device_node *node)
242 struct pit_data *data;
244 data = kzalloc(sizeof(*data), GFP_KERNEL);
248 data->base = of_iomap(node, 0);
250 pr_err("Could not map PIT address\n");
254 data->mck = of_clk_get(node, 0);
255 if (IS_ERR(data->mck))
256 /* Fallback on clkdev for !CCF-based boards */
257 data->mck = clk_get(NULL, "mck");
259 if (IS_ERR(data->mck)) {
260 pr_err("Unable to get mck clk\n");
261 return PTR_ERR(data->mck);
264 /* Get the interrupts property */
265 data->irq = irq_of_parse_and_map(node, 0);
267 pr_err("Unable to get IRQ from DT\n");
271 return at91sam926x_pit_common_init(data);
273 CLOCKSOURCE_OF_DECLARE_RET(at91sam926x_pit, "atmel,at91sam9260-pit",
274 at91sam926x_pit_dt_init);