xref: /openbmc/linux/arch/nios2/kernel/time.c (revision c819e2cf)
1 /*
2  * Copyright (C) 2013-2014 Altera Corporation
3  * Copyright (C) 2010 Tobias Klauser <tklauser@distanz.ch>
4  * Copyright (C) 2004 Microtronix Datacom Ltd.
5  *
6  * This file is subject to the terms and conditions of the GNU General Public
7  * License. See the file "COPYING" in the main directory of this archive
8  * for more details.
9  */
10 
11 #include <linux/interrupt.h>
12 #include <linux/clockchips.h>
13 #include <linux/clocksource.h>
14 #include <linux/delay.h>
15 #include <linux/of.h>
16 #include <linux/of_address.h>
17 #include <linux/of_irq.h>
18 #include <linux/io.h>
19 #include <linux/slab.h>
20 
21 #define ALTERA_TIMER_STATUS_REG		0
22 #define ALTERA_TIMER_CONTROL_REG	4
23 #define ALTERA_TIMER_PERIODL_REG	8
24 #define ALTERA_TIMER_PERIODH_REG	12
25 #define ALTERA_TIMER_SNAPL_REG		16
26 #define ALTERA_TIMER_SNAPH_REG		20
27 
28 #define ALTERA_TIMER_CONTROL_ITO_MSK	(0x1)
29 #define ALTERA_TIMER_CONTROL_CONT_MSK	(0x2)
30 #define ALTERA_TIMER_CONTROL_START_MSK	(0x4)
31 #define ALTERA_TIMER_CONTROL_STOP_MSK	(0x8)
32 
33 struct nios2_timer {
34 	void __iomem *base;
35 	unsigned long freq;
36 };
37 
38 struct nios2_clockevent_dev {
39 	struct nios2_timer timer;
40 	struct clock_event_device ced;
41 };
42 
43 struct nios2_clocksource {
44 	struct nios2_timer timer;
45 	struct clocksource cs;
46 };
47 
48 static inline struct nios2_clockevent_dev *
49 	to_nios2_clkevent(struct clock_event_device *evt)
50 {
51 	return container_of(evt, struct nios2_clockevent_dev, ced);
52 }
53 
54 static inline struct nios2_clocksource *
55 	to_nios2_clksource(struct clocksource *cs)
56 {
57 	return container_of(cs, struct nios2_clocksource, cs);
58 }
59 
60 static u16 timer_readw(struct nios2_timer *timer, u32 offs)
61 {
62 	return readw(timer->base + offs);
63 }
64 
65 static void timer_writew(struct nios2_timer *timer, u16 val, u32 offs)
66 {
67 	writew(val, timer->base + offs);
68 }
69 
70 static inline unsigned long read_timersnapshot(struct nios2_timer *timer)
71 {
72 	unsigned long count;
73 
74 	timer_writew(timer, 0, ALTERA_TIMER_SNAPL_REG);
75 	count = timer_readw(timer, ALTERA_TIMER_SNAPH_REG) << 16 |
76 		timer_readw(timer, ALTERA_TIMER_SNAPL_REG);
77 
78 	return count;
79 }
80 
81 static cycle_t nios2_timer_read(struct clocksource *cs)
82 {
83 	struct nios2_clocksource *nios2_cs = to_nios2_clksource(cs);
84 	unsigned long flags;
85 	u32 count;
86 
87 	local_irq_save(flags);
88 	count = read_timersnapshot(&nios2_cs->timer);
89 	local_irq_restore(flags);
90 
91 	/* Counter is counting down */
92 	return ~count;
93 }
94 
95 static struct nios2_clocksource nios2_cs = {
96 	.cs = {
97 		.name	= "nios2-clksrc",
98 		.rating	= 250,
99 		.read	= nios2_timer_read,
100 		.mask	= CLOCKSOURCE_MASK(32),
101 		.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
102 	},
103 };
104 
105 cycles_t get_cycles(void)
106 {
107 	return nios2_timer_read(&nios2_cs.cs);
108 }
109 
110 static void nios2_timer_start(struct nios2_timer *timer)
111 {
112 	u16 ctrl;
113 
114 	ctrl = timer_readw(timer, ALTERA_TIMER_CONTROL_REG);
115 	ctrl |= ALTERA_TIMER_CONTROL_START_MSK;
116 	timer_writew(timer, ctrl, ALTERA_TIMER_CONTROL_REG);
117 }
118 
119 static void nios2_timer_stop(struct nios2_timer *timer)
120 {
121 	u16 ctrl;
122 
123 	ctrl = timer_readw(timer, ALTERA_TIMER_CONTROL_REG);
124 	ctrl |= ALTERA_TIMER_CONTROL_STOP_MSK;
125 	timer_writew(timer, ctrl, ALTERA_TIMER_CONTROL_REG);
126 }
127 
128 static void nios2_timer_config(struct nios2_timer *timer, unsigned long period,
129 	enum clock_event_mode mode)
130 {
131 	u16 ctrl;
132 
133 	/* The timer's actual period is one cycle greater than the value
134 	 * stored in the period register. */
135 	 period--;
136 
137 	ctrl = timer_readw(timer, ALTERA_TIMER_CONTROL_REG);
138 	/* stop counter */
139 	timer_writew(timer, ctrl | ALTERA_TIMER_CONTROL_STOP_MSK,
140 		ALTERA_TIMER_CONTROL_REG);
141 
142 	/* write new count */
143 	timer_writew(timer, period, ALTERA_TIMER_PERIODL_REG);
144 	timer_writew(timer, period >> 16, ALTERA_TIMER_PERIODH_REG);
145 
146 	ctrl |= ALTERA_TIMER_CONTROL_START_MSK | ALTERA_TIMER_CONTROL_ITO_MSK;
147 	if (mode == CLOCK_EVT_MODE_PERIODIC)
148 		ctrl |= ALTERA_TIMER_CONTROL_CONT_MSK;
149 	else
150 		ctrl &= ~ALTERA_TIMER_CONTROL_CONT_MSK;
151 	timer_writew(timer, ctrl, ALTERA_TIMER_CONTROL_REG);
152 }
153 
154 static int nios2_timer_set_next_event(unsigned long delta,
155 	struct clock_event_device *evt)
156 {
157 	struct nios2_clockevent_dev *nios2_ced = to_nios2_clkevent(evt);
158 
159 	nios2_timer_config(&nios2_ced->timer, delta, evt->mode);
160 
161 	return 0;
162 }
163 
164 static void nios2_timer_set_mode(enum clock_event_mode mode,
165 	struct clock_event_device *evt)
166 {
167 	unsigned long period;
168 	struct nios2_clockevent_dev *nios2_ced = to_nios2_clkevent(evt);
169 	struct nios2_timer *timer = &nios2_ced->timer;
170 
171 	switch (mode) {
172 	case CLOCK_EVT_MODE_PERIODIC:
173 		period = DIV_ROUND_UP(timer->freq, HZ);
174 		nios2_timer_config(timer, period, CLOCK_EVT_MODE_PERIODIC);
175 		break;
176 	case CLOCK_EVT_MODE_ONESHOT:
177 	case CLOCK_EVT_MODE_UNUSED:
178 	case CLOCK_EVT_MODE_SHUTDOWN:
179 		nios2_timer_stop(timer);
180 		break;
181 	case CLOCK_EVT_MODE_RESUME:
182 		nios2_timer_start(timer);
183 		break;
184 	}
185 }
186 
187 irqreturn_t timer_interrupt(int irq, void *dev_id)
188 {
189 	struct clock_event_device *evt = (struct clock_event_device *) dev_id;
190 	struct nios2_clockevent_dev *nios2_ced = to_nios2_clkevent(evt);
191 
192 	/* Clear the interrupt condition */
193 	timer_writew(&nios2_ced->timer, 0, ALTERA_TIMER_STATUS_REG);
194 	evt->event_handler(evt);
195 
196 	return IRQ_HANDLED;
197 }
198 
199 static void __init nios2_timer_get_base_and_freq(struct device_node *np,
200 				void __iomem **base, u32 *freq)
201 {
202 	*base = of_iomap(np, 0);
203 	if (!*base)
204 		panic("Unable to map reg for %s\n", np->name);
205 
206 	if (of_property_read_u32(np, "clock-frequency", freq))
207 		panic("Unable to get %s clock frequency\n", np->name);
208 }
209 
210 static struct nios2_clockevent_dev nios2_ce = {
211 	.ced = {
212 		.name = "nios2-clkevent",
213 		.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
214 		.rating = 250,
215 		.shift = 32,
216 		.set_next_event = nios2_timer_set_next_event,
217 		.set_mode = nios2_timer_set_mode,
218 	},
219 };
220 
221 static __init void nios2_clockevent_init(struct device_node *timer)
222 {
223 	void __iomem *iobase;
224 	u32 freq;
225 	int irq;
226 
227 	nios2_timer_get_base_and_freq(timer, &iobase, &freq);
228 
229 	irq = irq_of_parse_and_map(timer, 0);
230 	if (!irq)
231 		panic("Unable to parse timer irq\n");
232 
233 	nios2_ce.timer.base = iobase;
234 	nios2_ce.timer.freq = freq;
235 
236 	nios2_ce.ced.cpumask = cpumask_of(0);
237 	nios2_ce.ced.irq = irq;
238 
239 	nios2_timer_stop(&nios2_ce.timer);
240 	/* clear pending interrupt */
241 	timer_writew(&nios2_ce.timer, 0, ALTERA_TIMER_STATUS_REG);
242 
243 	if (request_irq(irq, timer_interrupt, IRQF_TIMER, timer->name,
244 		&nios2_ce.ced))
245 		panic("Unable to setup timer irq\n");
246 
247 	clockevents_config_and_register(&nios2_ce.ced, freq, 1, ULONG_MAX);
248 }
249 
250 static __init void nios2_clocksource_init(struct device_node *timer)
251 {
252 	unsigned int ctrl;
253 	void __iomem *iobase;
254 	u32 freq;
255 
256 	nios2_timer_get_base_and_freq(timer, &iobase, &freq);
257 
258 	nios2_cs.timer.base = iobase;
259 	nios2_cs.timer.freq = freq;
260 
261 	clocksource_register_hz(&nios2_cs.cs, freq);
262 
263 	timer_writew(&nios2_cs.timer, USHRT_MAX, ALTERA_TIMER_PERIODL_REG);
264 	timer_writew(&nios2_cs.timer, USHRT_MAX, ALTERA_TIMER_PERIODH_REG);
265 
266 	/* interrupt disable + continuous + start */
267 	ctrl = ALTERA_TIMER_CONTROL_CONT_MSK | ALTERA_TIMER_CONTROL_START_MSK;
268 	timer_writew(&nios2_cs.timer, ctrl, ALTERA_TIMER_CONTROL_REG);
269 
270 	/* Calibrate the delay loop directly */
271 	lpj_fine = freq / HZ;
272 }
273 
274 /*
275  * The first timer instance will use as a clockevent. If there are two or
276  * more instances, the second one gets used as clocksource and all
277  * others are unused.
278 */
279 static void __init nios2_time_init(struct device_node *timer)
280 {
281 	static int num_called;
282 
283 	switch (num_called) {
284 	case 0:
285 		nios2_clockevent_init(timer);
286 		break;
287 	case 1:
288 		nios2_clocksource_init(timer);
289 		break;
290 	default:
291 		break;
292 	}
293 
294 	num_called++;
295 }
296 
297 void read_persistent_clock(struct timespec *ts)
298 {
299 	ts->tv_sec = mktime(2007, 1, 1, 0, 0, 0);
300 	ts->tv_nsec = 0;
301 }
302 
303 void __init time_init(void)
304 {
305 	clocksource_of_init();
306 }
307 
308 CLOCKSOURCE_OF_DECLARE(nios2_timer, "altr,timer-1.0", nios2_time_init);
309