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1/*
2 * at91sam926x_time.c - Periodic Interval Timer (PIT) for at91sam926x
3 *
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.
7 *
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.
11 */
12
13#define pr_fmt(fmt) "AT91: PIT: " fmt
14
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>
20#include <linux/of.h>
21#include <linux/of_address.h>
22#include <linux/of_irq.h>
23#include <linux/slab.h>
24
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 */
29
30#define AT91_PIT_SR 0x04 /* Status Register */
31#define AT91_PIT_PITS BIT(0) /* Timer Status */
32
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 */
37
38#define PIT_CPIV(x) ((x) & AT91_PIT_CPIV)
39#define PIT_PICNT(x) (((x) & AT91_PIT_PICNT) >> 20)
40
41struct pit_data {
42 struct clock_event_device clkevt;
43 struct clocksource clksrc;
44
45 void __iomem *base;
46 u32 cycle;
47 u32 cnt;
48 unsigned int irq;
49 struct clk *mck;
50};
51
52static inline struct pit_data *clksrc_to_pit_data(struct clocksource *clksrc)
53{
54 return container_of(clksrc, struct pit_data, clksrc);
55}
56
57static inline struct pit_data *clkevt_to_pit_data(struct clock_event_device *clkevt)
58{
59 return container_of(clkevt, struct pit_data, clkevt);
60}
61
62static inline unsigned int pit_read(void __iomem *base, unsigned int reg_offset)
63{
64 return readl_relaxed(base + reg_offset);
65}
66
67static inline void pit_write(void __iomem *base, unsigned int reg_offset, unsigned long value)
68{
69 writel_relaxed(value, base + reg_offset);
70}
71
72/*
73 * Clocksource: just a monotonic counter of MCK/16 cycles.
74 * We don't care whether or not PIT irqs are enabled.
75 */
76static u64 read_pit_clk(struct clocksource *cs)
77{
78 struct pit_data *data = clksrc_to_pit_data(cs);
79 unsigned long flags;
80 u32 elapsed;
81 u32 t;
82
83 raw_local_irq_save(flags);
84 elapsed = data->cnt;
85 t = pit_read(data->base, AT91_PIT_PIIR);
86 raw_local_irq_restore(flags);
87
88 elapsed += PIT_PICNT(t) * data->cycle;
89 elapsed += PIT_CPIV(t);
90 return elapsed;
91}
92
93static int pit_clkevt_shutdown(struct clock_event_device *dev)
94{
95 struct pit_data *data = clkevt_to_pit_data(dev);
96
97 /* disable irq, leaving the clocksource active */
98 pit_write(data->base, AT91_PIT_MR, (data->cycle - 1) | AT91_PIT_PITEN);
99 return 0;
100}
101
102/*
103 * Clockevent device: interrupts every 1/HZ (== pit_cycles * MCK/16)
104 */
105static int pit_clkevt_set_periodic(struct clock_event_device *dev)
106{
107 struct pit_data *data = clkevt_to_pit_data(dev);
108
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);
113 return 0;
114}
115
116static void at91sam926x_pit_suspend(struct clock_event_device *cedev)
117{
118 struct pit_data *data = clkevt_to_pit_data(cedev);
119
120 /* Disable timer */
121 pit_write(data->base, AT91_PIT_MR, 0);
122}
123
124static void at91sam926x_pit_reset(struct pit_data *data)
125{
126 /* Disable timer and irqs */
127 pit_write(data->base, AT91_PIT_MR, 0);
128
129 /* Clear any pending interrupts, wait for PIT to stop counting */
130 while (PIT_CPIV(pit_read(data->base, AT91_PIT_PIVR)) != 0)
131 cpu_relax();
132
133 /* Start PIT but don't enable IRQ */
134 pit_write(data->base, AT91_PIT_MR,
135 (data->cycle - 1) | AT91_PIT_PITEN);
136}
137
138static void at91sam926x_pit_resume(struct clock_event_device *cedev)
139{
140 struct pit_data *data = clkevt_to_pit_data(cedev);
141
142 at91sam926x_pit_reset(data);
143}
144
145/*
146 * IRQ handler for the timer.
147 */
148static irqreturn_t at91sam926x_pit_interrupt(int irq, void *dev_id)
149{
150 struct pit_data *data = dev_id;
151
152 /* The PIT interrupt may be disabled, and is shared */
153 if (clockevent_state_periodic(&data->clkevt) &&
154 (pit_read(data->base, AT91_PIT_SR) & AT91_PIT_PITS)) {
155 /* Get number of ticks performed before irq, and ack it */
156 data->cnt += data->cycle * PIT_PICNT(pit_read(data->base,
157 AT91_PIT_PIVR));
158 data->clkevt.event_handler(&data->clkevt);
159
160 return IRQ_HANDLED;
161 }
162
163 return IRQ_NONE;
164}
165
166/*
167 * Set up both clocksource and clockevent support.
168 */
169static int __init at91sam926x_pit_dt_init(struct device_node *node)
170{
171 unsigned long pit_rate;
172 unsigned bits;
173 int ret;
174 struct pit_data *data;
175
176 data = kzalloc(sizeof(*data), GFP_KERNEL);
177 if (!data)
178 return -ENOMEM;
179
180 data->base = of_iomap(node, 0);
181 if (!data->base) {
182 pr_err("Could not map PIT address\n");
183 ret = -ENXIO;
184 goto exit;
185 }
186
187 data->mck = of_clk_get(node, 0);
188 if (IS_ERR(data->mck)) {
189 pr_err("Unable to get mck clk\n");
190 ret = PTR_ERR(data->mck);
191 goto exit;
192 }
193
194 ret = clk_prepare_enable(data->mck);
195 if (ret) {
196 pr_err("Unable to enable mck\n");
197 goto exit;
198 }
199
200 /* Get the interrupts property */
201 data->irq = irq_of_parse_and_map(node, 0);
202 if (!data->irq) {
203 pr_err("Unable to get IRQ from DT\n");
204 ret = -EINVAL;
205 goto exit;
206 }
207
208 /*
209 * Use our actual MCK to figure out how many MCK/16 ticks per
210 * 1/HZ period (instead of a compile-time constant LATCH).
211 */
212 pit_rate = clk_get_rate(data->mck) / 16;
213 data->cycle = DIV_ROUND_CLOSEST(pit_rate, HZ);
214 WARN_ON(((data->cycle - 1) & ~AT91_PIT_PIV) != 0);
215
216 /* Initialize and enable the timer */
217 at91sam926x_pit_reset(data);
218
219 /*
220 * Register clocksource. The high order bits of PIV are unused,
221 * so this isn't a 32-bit counter unless we get clockevent irqs.
222 */
223 bits = 12 /* PICNT */ + ilog2(data->cycle) /* PIV */;
224 data->clksrc.mask = CLOCKSOURCE_MASK(bits);
225 data->clksrc.name = "pit";
226 data->clksrc.rating = 175;
227 data->clksrc.read = read_pit_clk;
228 data->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
229
230 ret = clocksource_register_hz(&data->clksrc, pit_rate);
231 if (ret) {
232 pr_err("Failed to register clocksource\n");
233 goto exit;
234 }
235
236 /* Set up irq handler */
237 ret = request_irq(data->irq, at91sam926x_pit_interrupt,
238 IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
239 "at91_tick", data);
240 if (ret) {
241 pr_err("Unable to setup IRQ\n");
242 clocksource_unregister(&data->clksrc);
243 goto exit;
244 }
245
246 /* Set up and register clockevents */
247 data->clkevt.name = "pit";
248 data->clkevt.features = CLOCK_EVT_FEAT_PERIODIC;
249 data->clkevt.shift = 32;
250 data->clkevt.mult = div_sc(pit_rate, NSEC_PER_SEC, data->clkevt.shift);
251 data->clkevt.rating = 100;
252 data->clkevt.cpumask = cpumask_of(0);
253
254 data->clkevt.set_state_shutdown = pit_clkevt_shutdown;
255 data->clkevt.set_state_periodic = pit_clkevt_set_periodic;
256 data->clkevt.resume = at91sam926x_pit_resume;
257 data->clkevt.suspend = at91sam926x_pit_suspend;
258 clockevents_register_device(&data->clkevt);
259
260 return 0;
261
262exit:
263 kfree(data);
264 return ret;
265}
266TIMER_OF_DECLARE(at91sam926x_pit, "atmel,at91sam9260-pit",
267 at91sam926x_pit_dt_init);
268

Warning: That file was not part of the compilation database. It may have many parsing errors.