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
33struct nios2_timer {
34	void __iomem *base;
35	unsigned long freq;
36};
37
38struct nios2_clockevent_dev {
39	struct nios2_timer timer;
40	struct clock_event_device ced;
41};
42
43struct nios2_clocksource {
44	struct nios2_timer timer;
45	struct clocksource cs;
46};
47
48static 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
54static inline struct nios2_clocksource *
55	to_nios2_clksource(struct clocksource *cs)
56{
57	return container_of(cs, struct nios2_clocksource, cs);
58}
59
60static u16 timer_readw(struct nios2_timer *timer, u32 offs)
61{
62	return readw(timer->base + offs);
63}
64
65static void timer_writew(struct nios2_timer *timer, u16 val, u32 offs)
66{
67	writew(val, timer->base + offs);
68}
69
70static 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
81static 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
95static 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
105cycles_t get_cycles(void)
106{
107	return nios2_timer_read(&nios2_cs.cs);
108}
109
110static 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
119static 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
128static 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
154static 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
164static 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
187irqreturn_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
199static 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
210static 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
221static __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
250static __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*/
279static 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
297void 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
303void __init time_init(void)
304{
305	clocksource_of_init();
306}
307
308CLOCKSOURCE_OF_DECLARE(nios2_timer, "altr,timer-1.0", nios2_time_init);
309