xref: /openbmc/linux/arch/arm/mach-spear/time.c (revision afb46f79) 
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 void clockevent_set_mode(enum clock_event_mode mode,
70 				struct clock_event_device *clk_event_dev);
71 static int clockevent_next_event(unsigned long evt,
72 				 struct clock_event_device *clk_event_dev);
73 
74 static void spear_clocksource_init(void)
75 {
76 	u32 tick_rate;
77 	u16 val;
78 
79 	/* program the prescaler (/256)*/
80 	writew(CTRL_PRESCALER256, gpt_base + CR(CLKSRC));
81 
82 	/* find out actual clock driving Timer */
83 	tick_rate = clk_get_rate(gpt_clk);
84 	tick_rate >>= CTRL_PRESCALER256;
85 
86 	writew(0xFFFF, gpt_base + LOAD(CLKSRC));
87 
88 	val = readw(gpt_base + CR(CLKSRC));
89 	val &= ~CTRL_ONE_SHOT;	/* autoreload mode */
90 	val |= CTRL_ENABLE ;
91 	writew(val, gpt_base + CR(CLKSRC));
92 
93 	/* register the clocksource */
94 	clocksource_mmio_init(gpt_base + COUNT(CLKSRC), "tmr1", tick_rate,
95 		200, 16, clocksource_mmio_readw_up);
96 }
97 
98 static struct clock_event_device clkevt = {
99 	.name = "tmr0",
100 	.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
101 	.set_mode = clockevent_set_mode,
102 	.set_next_event = clockevent_next_event,
103 	.shift = 0,	/* to be computed */
104 };
105 
106 static void clockevent_set_mode(enum clock_event_mode mode,
107 				struct clock_event_device *clk_event_dev)
108 {
109 	u32 period;
110 	u16 val;
111 
112 	/* stop the timer */
113 	val = readw(gpt_base + CR(CLKEVT));
114 	val &= ~CTRL_ENABLE;
115 	writew(val, gpt_base + CR(CLKEVT));
116 
117 	switch (mode) {
118 	case CLOCK_EVT_MODE_PERIODIC:
119 		period = clk_get_rate(gpt_clk) / HZ;
120 		period >>= CTRL_PRESCALER16;
121 		writew(period, gpt_base + LOAD(CLKEVT));
122 
123 		val = readw(gpt_base + CR(CLKEVT));
124 		val &= ~CTRL_ONE_SHOT;
125 		val |= CTRL_ENABLE | CTRL_INT_ENABLE;
126 		writew(val, gpt_base + CR(CLKEVT));
127 
128 		break;
129 	case CLOCK_EVT_MODE_ONESHOT:
130 		val = readw(gpt_base + CR(CLKEVT));
131 		val |= CTRL_ONE_SHOT;
132 		writew(val, gpt_base + CR(CLKEVT));
133 
134 		break;
135 	case CLOCK_EVT_MODE_UNUSED:
136 	case CLOCK_EVT_MODE_SHUTDOWN:
137 	case CLOCK_EVT_MODE_RESUME:
138 
139 		break;
140 	default:
141 		pr_err("Invalid mode requested\n");
142 		break;
143 	}
144 }
145 
146 static int clockevent_next_event(unsigned long cycles,
147 				 struct clock_event_device *clk_event_dev)
148 {
149 	u16 val = readw(gpt_base + CR(CLKEVT));
150 
151 	if (val & CTRL_ENABLE)
152 		writew(val & ~CTRL_ENABLE, gpt_base + CR(CLKEVT));
153 
154 	writew(cycles, gpt_base + LOAD(CLKEVT));
155 
156 	val |= CTRL_ENABLE | CTRL_INT_ENABLE;
157 	writew(val, gpt_base + CR(CLKEVT));
158 
159 	return 0;
160 }
161 
162 static irqreturn_t spear_timer_interrupt(int irq, void *dev_id)
163 {
164 	struct clock_event_device *evt = &clkevt;
165 
166 	writew(INT_STATUS, gpt_base + IR(CLKEVT));
167 
168 	evt->event_handler(evt);
169 
170 	return IRQ_HANDLED;
171 }
172 
173 static struct irqaction spear_timer_irq = {
174 	.name = "timer",
175 	.flags = IRQF_TIMER,
176 	.handler = spear_timer_interrupt
177 };
178 
179 static void __init spear_clockevent_init(int irq)
180 {
181 	u32 tick_rate;
182 
183 	/* program the prescaler */
184 	writew(CTRL_PRESCALER16, gpt_base + CR(CLKEVT));
185 
186 	tick_rate = clk_get_rate(gpt_clk);
187 	tick_rate >>= CTRL_PRESCALER16;
188 
189 	clkevt.cpumask = cpumask_of(0);
190 
191 	clockevents_config_and_register(&clkevt, tick_rate, 3, 0xfff0);
192 
193 	setup_irq(irq, &spear_timer_irq);
194 }
195 
196 const static struct of_device_id timer_of_match[] __initconst = {
197 	{ .compatible = "st,spear-timer", },
198 	{ },
199 };
200 
201 void __init spear_setup_of_timer(void)
202 {
203 	struct device_node *np;
204 	int irq, ret;
205 
206 	np = of_find_matching_node(NULL, timer_of_match);
207 	if (!np) {
208 		pr_err("%s: No timer passed via DT\n", __func__);
209 		return;
210 	}
211 
212 	irq = irq_of_parse_and_map(np, 0);
213 	if (!irq) {
214 		pr_err("%s: No irq passed for timer via DT\n", __func__);
215 		return;
216 	}
217 
218 	gpt_base = of_iomap(np, 0);
219 	if (!gpt_base) {
220 		pr_err("%s: of iomap failed\n", __func__);
221 		return;
222 	}
223 
224 	gpt_clk = clk_get_sys("gpt0", NULL);
225 	if (!gpt_clk) {
226 		pr_err("%s:couldn't get clk for gpt\n", __func__);
227 		goto err_iomap;
228 	}
229 
230 	ret = clk_prepare_enable(gpt_clk);
231 	if (ret < 0) {
232 		pr_err("%s:couldn't prepare-enable gpt clock\n", __func__);
233 		goto err_prepare_enable_clk;
234 	}
235 
236 	spear_clockevent_init(irq);
237 	spear_clocksource_init();
238 
239 	return;
240 
241 err_prepare_enable_clk:
242 	clk_put(gpt_clk);
243 err_iomap:
244 	iounmap(gpt_base);
245 }
246