xref: /openbmc/linux/arch/arm/mach-spear/time.c (revision 4e1a33b1) 
1 /*
2  * arch/arm/plat-spear/time.c
3  *
4  * Copyright (C) 2010 ST Microelectronics
5  * Shiraz Hashim<shiraz.linux.kernel@gmail.com>
6  *
7  * This file is licensed under the terms of the GNU General Public
8  * License version 2. This program is licensed "as is" without any
9  * warranty of any kind, whether express or implied.
10  */
11 
12 #include <linux/clk.h>
13 #include <linux/clockchips.h>
14 #include <linux/clocksource.h>
15 #include <linux/err.h>
16 #include <linux/init.h>
17 #include <linux/interrupt.h>
18 #include <linux/ioport.h>
19 #include <linux/io.h>
20 #include <linux/kernel.h>
21 #include <linux/of_irq.h>
22 #include <linux/of_address.h>
23 #include <linux/time.h>
24 #include <linux/irq.h>
25 #include <asm/mach/time.h>
26 #include "generic.h"
27 
28 /*
29  * We would use TIMER0 and TIMER1 as clockevent and clocksource.
30  * Timer0 and Timer1 both belong to same gpt block in cpu subbsystem. Further
31  * they share same functional clock. Any change in one's functional clock will
32  * also affect other timer.
33  */
34 
35 #define CLKEVT	0	/* gpt0, channel0 as clockevent */
36 #define CLKSRC	1	/* gpt0, channel1 as clocksource */
37 
38 /* Register offsets, x is channel number */
39 #define CR(x)		((x) * 0x80 + 0x80)
40 #define IR(x)		((x) * 0x80 + 0x84)
41 #define LOAD(x)		((x) * 0x80 + 0x88)
42 #define COUNT(x)	((x) * 0x80 + 0x8C)
43 
44 /* Reg bit definitions */
45 #define CTRL_INT_ENABLE		0x0100
46 #define CTRL_ENABLE		0x0020
47 #define CTRL_ONE_SHOT		0x0010
48 
49 #define CTRL_PRESCALER1		0x0
50 #define CTRL_PRESCALER2		0x1
51 #define CTRL_PRESCALER4		0x2
52 #define CTRL_PRESCALER8		0x3
53 #define CTRL_PRESCALER16	0x4
54 #define CTRL_PRESCALER32	0x5
55 #define CTRL_PRESCALER64	0x6
56 #define CTRL_PRESCALER128	0x7
57 #define CTRL_PRESCALER256	0x8
58 
59 #define INT_STATUS		0x1
60 
61 /*
62  * Minimum clocksource/clockevent timer range in seconds
63  */
64 #define SPEAR_MIN_RANGE 4
65 
66 static __iomem void *gpt_base;
67 static struct clk *gpt_clk;
68 
69 static int clockevent_next_event(unsigned long evt,
70 				 struct clock_event_device *clk_event_dev);
71 
72 static void __init spear_clocksource_init(void)
73 {
74 	u32 tick_rate;
75 	u16 val;
76 
77 	/* program the prescaler (/256)*/
78 	writew(CTRL_PRESCALER256, gpt_base + CR(CLKSRC));
79 
80 	/* find out actual clock driving Timer */
81 	tick_rate = clk_get_rate(gpt_clk);
82 	tick_rate >>= CTRL_PRESCALER256;
83 
84 	writew(0xFFFF, gpt_base + LOAD(CLKSRC));
85 
86 	val = readw(gpt_base + CR(CLKSRC));
87 	val &= ~CTRL_ONE_SHOT;	/* autoreload mode */
88 	val |= CTRL_ENABLE ;
89 	writew(val, gpt_base + CR(CLKSRC));
90 
91 	/* register the clocksource */
92 	clocksource_mmio_init(gpt_base + COUNT(CLKSRC), "tmr1", tick_rate,
93 		200, 16, clocksource_mmio_readw_up);
94 }
95 
96 static inline void timer_shutdown(struct clock_event_device *evt)
97 {
98 	u16 val = readw(gpt_base + CR(CLKEVT));
99 
100 	/* stop the timer */
101 	val &= ~CTRL_ENABLE;
102 	writew(val, gpt_base + CR(CLKEVT));
103 }
104 
105 static int spear_shutdown(struct clock_event_device *evt)
106 {
107 	timer_shutdown(evt);
108 
109 	return 0;
110 }
111 
112 static int spear_set_oneshot(struct clock_event_device *evt)
113 {
114 	u16 val;
115 
116 	/* stop the timer */
117 	timer_shutdown(evt);
118 
119 	val = readw(gpt_base + CR(CLKEVT));
120 	val |= CTRL_ONE_SHOT;
121 	writew(val, gpt_base + CR(CLKEVT));
122 
123 	return 0;
124 }
125 
126 static int spear_set_periodic(struct clock_event_device *evt)
127 {
128 	u32 period;
129 	u16 val;
130 
131 	/* stop the timer */
132 	timer_shutdown(evt);
133 
134 	period = clk_get_rate(gpt_clk) / HZ;
135 	period >>= CTRL_PRESCALER16;
136 	writew(period, gpt_base + LOAD(CLKEVT));
137 
138 	val = readw(gpt_base + CR(CLKEVT));
139 	val &= ~CTRL_ONE_SHOT;
140 	val |= CTRL_ENABLE | CTRL_INT_ENABLE;
141 	writew(val, gpt_base + CR(CLKEVT));
142 
143 	return 0;
144 }
145 
146 static struct clock_event_device clkevt = {
147 	.name = "tmr0",
148 	.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
149 	.set_state_shutdown = spear_shutdown,
150 	.set_state_periodic = spear_set_periodic,
151 	.set_state_oneshot = spear_set_oneshot,
152 	.tick_resume = spear_shutdown,
153 	.set_next_event = clockevent_next_event,
154 	.shift = 0,	/* to be computed */
155 };
156 
157 static int clockevent_next_event(unsigned long cycles,
158 				 struct clock_event_device *clk_event_dev)
159 {
160 	u16 val = readw(gpt_base + CR(CLKEVT));
161 
162 	if (val & CTRL_ENABLE)
163 		writew(val & ~CTRL_ENABLE, gpt_base + CR(CLKEVT));
164 
165 	writew(cycles, gpt_base + LOAD(CLKEVT));
166 
167 	val |= CTRL_ENABLE | CTRL_INT_ENABLE;
168 	writew(val, gpt_base + CR(CLKEVT));
169 
170 	return 0;
171 }
172 
173 static irqreturn_t spear_timer_interrupt(int irq, void *dev_id)
174 {
175 	struct clock_event_device *evt = &clkevt;
176 
177 	writew(INT_STATUS, gpt_base + IR(CLKEVT));
178 
179 	evt->event_handler(evt);
180 
181 	return IRQ_HANDLED;
182 }
183 
184 static struct irqaction spear_timer_irq = {
185 	.name = "timer",
186 	.flags = IRQF_TIMER,
187 	.handler = spear_timer_interrupt
188 };
189 
190 static void __init spear_clockevent_init(int irq)
191 {
192 	u32 tick_rate;
193 
194 	/* program the prescaler */
195 	writew(CTRL_PRESCALER16, gpt_base + CR(CLKEVT));
196 
197 	tick_rate = clk_get_rate(gpt_clk);
198 	tick_rate >>= CTRL_PRESCALER16;
199 
200 	clkevt.cpumask = cpumask_of(0);
201 
202 	clockevents_config_and_register(&clkevt, tick_rate, 3, 0xfff0);
203 
204 	setup_irq(irq, &spear_timer_irq);
205 }
206 
207 static const struct of_device_id const timer_of_match[] __initconst = {
208 	{ .compatible = "st,spear-timer", },
209 	{ },
210 };
211 
212 void __init spear_setup_of_timer(void)
213 {
214 	struct device_node *np;
215 	int irq, ret;
216 
217 	np = of_find_matching_node(NULL, timer_of_match);
218 	if (!np) {
219 		pr_err("%s: No timer passed via DT\n", __func__);
220 		return;
221 	}
222 
223 	irq = irq_of_parse_and_map(np, 0);
224 	if (!irq) {
225 		pr_err("%s: No irq passed for timer via DT\n", __func__);
226 		return;
227 	}
228 
229 	gpt_base = of_iomap(np, 0);
230 	if (!gpt_base) {
231 		pr_err("%s: of iomap failed\n", __func__);
232 		return;
233 	}
234 
235 	gpt_clk = clk_get_sys("gpt0", NULL);
236 	if (IS_ERR(gpt_clk)) {
237 		pr_err("%s:couldn't get clk for gpt\n", __func__);
238 		goto err_iomap;
239 	}
240 
241 	ret = clk_prepare_enable(gpt_clk);
242 	if (ret < 0) {
243 		pr_err("%s:couldn't prepare-enable gpt clock\n", __func__);
244 		goto err_prepare_enable_clk;
245 	}
246 
247 	spear_clockevent_init(irq);
248 	spear_clocksource_init();
249 
250 	return;
251 
252 err_prepare_enable_clk:
253 	clk_put(gpt_clk);
254 err_iomap:
255 	iounmap(gpt_base);
256 }
257