1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * at91sam926x_time.c - Periodic Interval Timer (PIT) for at91sam926x
4  *
5  * Copyright (C) 2005-2006 M. Amine SAYA, ATMEL Rousset, France
6  * Revision	 2005 M. Nicolas Diremdjian, ATMEL Rousset, France
7  * Converted to ClockSource/ClockEvents by David Brownell.
8  */
9 
10 #define pr_fmt(fmt)	"AT91: PIT: " fmt
11 
12 #include <linux/clk.h>
13 #include <linux/clockchips.h>
14 #include <linux/interrupt.h>
15 #include <linux/irq.h>
16 #include <linux/kernel.h>
17 #include <linux/of.h>
18 #include <linux/of_address.h>
19 #include <linux/of_irq.h>
20 #include <linux/slab.h>
21 
22 #define AT91_PIT_MR		0x00			/* Mode Register */
23 #define AT91_PIT_PITIEN			BIT(25)			/* Timer Interrupt Enable */
24 #define AT91_PIT_PITEN			BIT(24)			/* Timer Enabled */
25 #define AT91_PIT_PIV			GENMASK(19, 0)		/* Periodic Interval Value */
26 
27 #define AT91_PIT_SR		0x04			/* Status Register */
28 #define AT91_PIT_PITS			BIT(0)			/* Timer Status */
29 
30 #define AT91_PIT_PIVR		0x08			/* Periodic Interval Value Register */
31 #define AT91_PIT_PIIR		0x0c			/* Periodic Interval Image Register */
32 #define AT91_PIT_PICNT			GENMASK(31, 20)		/* Interval Counter */
33 #define AT91_PIT_CPIV			GENMASK(19, 0)		/* Inverval Value */
34 
35 #define PIT_CPIV(x)	((x) & AT91_PIT_CPIV)
36 #define PIT_PICNT(x)	(((x) & AT91_PIT_PICNT) >> 20)
37 
38 struct pit_data {
39 	struct clock_event_device	clkevt;
40 	struct clocksource		clksrc;
41 
42 	void __iomem	*base;
43 	u32		cycle;
44 	u32		cnt;
45 	unsigned int	irq;
46 	struct clk	*mck;
47 };
48 
49 static inline struct pit_data *clksrc_to_pit_data(struct clocksource *clksrc)
50 {
51 	return container_of(clksrc, struct pit_data, clksrc);
52 }
53 
54 static inline struct pit_data *clkevt_to_pit_data(struct clock_event_device *clkevt)
55 {
56 	return container_of(clkevt, struct pit_data, clkevt);
57 }
58 
59 static inline unsigned int pit_read(void __iomem *base, unsigned int reg_offset)
60 {
61 	return readl_relaxed(base + reg_offset);
62 }
63 
64 static inline void pit_write(void __iomem *base, unsigned int reg_offset, unsigned long value)
65 {
66 	writel_relaxed(value, base + reg_offset);
67 }
68 
69 /*
70  * Clocksource:  just a monotonic counter of MCK/16 cycles.
71  * We don't care whether or not PIT irqs are enabled.
72  */
73 static u64 read_pit_clk(struct clocksource *cs)
74 {
75 	struct pit_data *data = clksrc_to_pit_data(cs);
76 	unsigned long flags;
77 	u32 elapsed;
78 	u32 t;
79 
80 	raw_local_irq_save(flags);
81 	elapsed = data->cnt;
82 	t = pit_read(data->base, AT91_PIT_PIIR);
83 	raw_local_irq_restore(flags);
84 
85 	elapsed += PIT_PICNT(t) * data->cycle;
86 	elapsed += PIT_CPIV(t);
87 	return elapsed;
88 }
89 
90 static int pit_clkevt_shutdown(struct clock_event_device *dev)
91 {
92 	struct pit_data *data = clkevt_to_pit_data(dev);
93 
94 	/* disable irq, leaving the clocksource active */
95 	pit_write(data->base, AT91_PIT_MR, (data->cycle - 1) | AT91_PIT_PITEN);
96 	return 0;
97 }
98 
99 /*
100  * Clockevent device:  interrupts every 1/HZ (== pit_cycles * MCK/16)
101  */
102 static int pit_clkevt_set_periodic(struct clock_event_device *dev)
103 {
104 	struct pit_data *data = clkevt_to_pit_data(dev);
105 
106 	/* update clocksource counter */
107 	data->cnt += data->cycle * PIT_PICNT(pit_read(data->base, AT91_PIT_PIVR));
108 	pit_write(data->base, AT91_PIT_MR,
109 		  (data->cycle - 1) | AT91_PIT_PITEN | AT91_PIT_PITIEN);
110 	return 0;
111 }
112 
113 static void at91sam926x_pit_suspend(struct clock_event_device *cedev)
114 {
115 	struct pit_data *data = clkevt_to_pit_data(cedev);
116 
117 	/* Disable timer */
118 	pit_write(data->base, AT91_PIT_MR, 0);
119 }
120 
121 static void at91sam926x_pit_reset(struct pit_data *data)
122 {
123 	/* Disable timer and irqs */
124 	pit_write(data->base, AT91_PIT_MR, 0);
125 
126 	/* Clear any pending interrupts, wait for PIT to stop counting */
127 	while (PIT_CPIV(pit_read(data->base, AT91_PIT_PIVR)) != 0)
128 		cpu_relax();
129 
130 	/* Start PIT but don't enable IRQ */
131 	pit_write(data->base, AT91_PIT_MR,
132 		  (data->cycle - 1) | AT91_PIT_PITEN);
133 }
134 
135 static void at91sam926x_pit_resume(struct clock_event_device *cedev)
136 {
137 	struct pit_data *data = clkevt_to_pit_data(cedev);
138 
139 	at91sam926x_pit_reset(data);
140 }
141 
142 /*
143  * IRQ handler for the timer.
144  */
145 static irqreturn_t at91sam926x_pit_interrupt(int irq, void *dev_id)
146 {
147 	struct pit_data *data = dev_id;
148 
149 	/* The PIT interrupt may be disabled, and is shared */
150 	if (clockevent_state_periodic(&data->clkevt) &&
151 	    (pit_read(data->base, AT91_PIT_SR) & AT91_PIT_PITS)) {
152 		/* Get number of ticks performed before irq, and ack it */
153 		data->cnt += data->cycle * PIT_PICNT(pit_read(data->base,
154 							      AT91_PIT_PIVR));
155 		data->clkevt.event_handler(&data->clkevt);
156 
157 		return IRQ_HANDLED;
158 	}
159 
160 	return IRQ_NONE;
161 }
162 
163 /*
164  * Set up both clocksource and clockevent support.
165  */
166 static int __init at91sam926x_pit_dt_init(struct device_node *node)
167 {
168 	unsigned long   pit_rate;
169 	unsigned        bits;
170 	int             ret;
171 	struct pit_data *data;
172 
173 	data = kzalloc(sizeof(*data), GFP_KERNEL);
174 	if (!data)
175 		return -ENOMEM;
176 
177 	data->base = of_iomap(node, 0);
178 	if (!data->base) {
179 		pr_err("Could not map PIT address\n");
180 		ret = -ENXIO;
181 		goto exit;
182 	}
183 
184 	data->mck = of_clk_get(node, 0);
185 	if (IS_ERR(data->mck)) {
186 		pr_err("Unable to get mck clk\n");
187 		ret = PTR_ERR(data->mck);
188 		goto exit;
189 	}
190 
191 	ret = clk_prepare_enable(data->mck);
192 	if (ret) {
193 		pr_err("Unable to enable mck\n");
194 		goto exit;
195 	}
196 
197 	/* Get the interrupts property */
198 	data->irq = irq_of_parse_and_map(node, 0);
199 	if (!data->irq) {
200 		pr_err("Unable to get IRQ from DT\n");
201 		ret = -EINVAL;
202 		goto exit;
203 	}
204 
205 	/*
206 	 * Use our actual MCK to figure out how many MCK/16 ticks per
207 	 * 1/HZ period (instead of a compile-time constant LATCH).
208 	 */
209 	pit_rate = clk_get_rate(data->mck) / 16;
210 	data->cycle = DIV_ROUND_CLOSEST(pit_rate, HZ);
211 	WARN_ON(((data->cycle - 1) & ~AT91_PIT_PIV) != 0);
212 
213 	/* Initialize and enable the timer */
214 	at91sam926x_pit_reset(data);
215 
216 	/*
217 	 * Register clocksource.  The high order bits of PIV are unused,
218 	 * so this isn't a 32-bit counter unless we get clockevent irqs.
219 	 */
220 	bits = 12 /* PICNT */ + ilog2(data->cycle) /* PIV */;
221 	data->clksrc.mask = CLOCKSOURCE_MASK(bits);
222 	data->clksrc.name = "pit";
223 	data->clksrc.rating = 175;
224 	data->clksrc.read = read_pit_clk;
225 	data->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
226 
227 	ret = clocksource_register_hz(&data->clksrc, pit_rate);
228 	if (ret) {
229 		pr_err("Failed to register clocksource\n");
230 		goto exit;
231 	}
232 
233 	/* Set up irq handler */
234 	ret = request_irq(data->irq, at91sam926x_pit_interrupt,
235 			  IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
236 			  "at91_tick", data);
237 	if (ret) {
238 		pr_err("Unable to setup IRQ\n");
239 		clocksource_unregister(&data->clksrc);
240 		goto exit;
241 	}
242 
243 	/* Set up and register clockevents */
244 	data->clkevt.name = "pit";
245 	data->clkevt.features = CLOCK_EVT_FEAT_PERIODIC;
246 	data->clkevt.shift = 32;
247 	data->clkevt.mult = div_sc(pit_rate, NSEC_PER_SEC, data->clkevt.shift);
248 	data->clkevt.rating = 100;
249 	data->clkevt.cpumask = cpumask_of(0);
250 
251 	data->clkevt.set_state_shutdown = pit_clkevt_shutdown;
252 	data->clkevt.set_state_periodic = pit_clkevt_set_periodic;
253 	data->clkevt.resume = at91sam926x_pit_resume;
254 	data->clkevt.suspend = at91sam926x_pit_suspend;
255 	clockevents_register_device(&data->clkevt);
256 
257 	return 0;
258 
259 exit:
260 	kfree(data);
261 	return ret;
262 }
263 TIMER_OF_DECLARE(at91sam926x_pit, "atmel,at91sam9260-pit",
264 		       at91sam926x_pit_dt_init);
265