Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1/*
2 * Copyright 2012-2013 Freescale Semiconductor, Inc.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
8 */
9
10#include <linux/interrupt.h>
11#include <linux/clockchips.h>
12#include <linux/clk.h>
13#include <linux/of_address.h>
14#include <linux/of_irq.h>
15#include <linux/sched_clock.h>
16
17/*
18 * Each pit takes 0x10 Bytes register space
19 */
20#define PITMCR 0x00
21#define PIT0_OFFSET 0x100
22#define PITn_OFFSET(n) (PIT0_OFFSET + 0x10 * (n))
23#define PITLDVAL 0x00
24#define PITCVAL 0x04
25#define PITTCTRL 0x08
26#define PITTFLG 0x0c
27
28#define PITMCR_MDIS (0x1 << 1)
29
30#define PITTCTRL_TEN (0x1 << 0)
31#define PITTCTRL_TIE (0x1 << 1)
32#define PITCTRL_CHN (0x1 << 2)
33
34#define PITTFLG_TIF 0x1
35
36static void __iomem *clksrc_base;
37static void __iomem *clkevt_base;
38static unsigned long cycle_per_jiffy;
39
40static inline void pit_timer_enable(void)
41{
42 __raw_writel(PITTCTRL_TEN | PITTCTRL_TIE, clkevt_base + PITTCTRL);
43}
44
45static inline void pit_timer_disable(void)
46{
47 __raw_writel(0, clkevt_base + PITTCTRL);
48}
49
50static inline void pit_irq_acknowledge(void)
51{
52 __raw_writel(PITTFLG_TIF, clkevt_base + PITTFLG);
53}
54
55static u64 notrace pit_read_sched_clock(void)
56{
57 return ~__raw_readl(clksrc_base + PITCVAL);
58}
59
60static int __init pit_clocksource_init(unsigned long rate)
61{
62 /* set the max load value and start the clock source counter */
63 __raw_writel(0, clksrc_base + PITTCTRL);
64 __raw_writel(~0UL, clksrc_base + PITLDVAL);
65 __raw_writel(PITTCTRL_TEN, clksrc_base + PITTCTRL);
66
67 sched_clock_register(pit_read_sched_clock, 32, rate);
68 return clocksource_mmio_init(clksrc_base + PITCVAL, "vf-pit", rate,
69 300, 32, clocksource_mmio_readl_down);
70}
71
72static int pit_set_next_event(unsigned long delta,
73 struct clock_event_device *unused)
74{
75 /*
76 * set a new value to PITLDVAL register will not restart the timer,
77 * to abort the current cycle and start a timer period with the new
78 * value, the timer must be disabled and enabled again.
79 * and the PITLAVAL should be set to delta minus one according to pit
80 * hardware requirement.
81 */
82 pit_timer_disable();
83 __raw_writel(delta - 1, clkevt_base + PITLDVAL);
84 pit_timer_enable();
85
86 return 0;
87}
88
89static int pit_shutdown(struct clock_event_device *evt)
90{
91 pit_timer_disable();
92 return 0;
93}
94
95static int pit_set_periodic(struct clock_event_device *evt)
96{
97 pit_set_next_event(cycle_per_jiffy, evt);
98 return 0;
99}
100
101static irqreturn_t pit_timer_interrupt(int irq, void *dev_id)
102{
103 struct clock_event_device *evt = dev_id;
104
105 pit_irq_acknowledge();
106
107 /*
108 * pit hardware doesn't support oneshot, it will generate an interrupt
109 * and reload the counter value from PITLDVAL when PITCVAL reach zero,
110 * and start the counter again. So software need to disable the timer
111 * to stop the counter loop in ONESHOT mode.
112 */
113 if (likely(clockevent_state_oneshot(evt)))
114 pit_timer_disable();
115
116 evt->event_handler(evt);
117
118 return IRQ_HANDLED;
119}
120
121static struct clock_event_device clockevent_pit = {
122 .name = "VF pit timer",
123 .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
124 .set_state_shutdown = pit_shutdown,
125 .set_state_periodic = pit_set_periodic,
126 .set_next_event = pit_set_next_event,
127 .rating = 300,
128};
129
130static struct irqaction pit_timer_irq = {
131 .name = "VF pit timer",
132 .flags = IRQF_TIMER | IRQF_IRQPOLL,
133 .handler = pit_timer_interrupt,
134 .dev_id = &clockevent_pit,
135};
136
137static int __init pit_clockevent_init(unsigned long rate, int irq)
138{
139 __raw_writel(0, clkevt_base + PITTCTRL);
140 __raw_writel(PITTFLG_TIF, clkevt_base + PITTFLG);
141
142 BUG_ON(setup_irq(irq, &pit_timer_irq));
143
144 clockevent_pit.cpumask = cpumask_of(0);
145 clockevent_pit.irq = irq;
146 /*
147 * The value for the LDVAL register trigger is calculated as:
148 * LDVAL trigger = (period / clock period) - 1
149 * The pit is a 32-bit down count timer, when the conter value
150 * reaches 0, it will generate an interrupt, thus the minimal
151 * LDVAL trigger value is 1. And then the min_delta is
152 * minimal LDVAL trigger value + 1, and the max_delta is full 32-bit.
153 */
154 clockevents_config_and_register(&clockevent_pit, rate, 2, 0xffffffff);
155
156 return 0;
157}
158
159static int __init pit_timer_init(struct device_node *np)
160{
161 struct clk *pit_clk;
162 void __iomem *timer_base;
163 unsigned long clk_rate;
164 int irq, ret;
165
166 timer_base = of_iomap(np, 0);
167 if (!timer_base) {
168 pr_err("Failed to iomap");
169 return -ENXIO;
170 }
171
172 /*
173 * PIT0 and PIT1 can be chained to build a 64-bit timer,
174 * so choose PIT2 as clocksource, PIT3 as clockevent device,
175 * and leave PIT0 and PIT1 unused for anyone else who needs them.
176 */
177 clksrc_base = timer_base + PITn_OFFSET(2);
178 clkevt_base = timer_base + PITn_OFFSET(3);
179
180 irq = irq_of_parse_and_map(np, 0);
181 if (irq <= 0)
182 return -EINVAL;
183
184 pit_clk = of_clk_get(np, 0);
185 if (IS_ERR(pit_clk))
186 return PTR_ERR(pit_clk);
187
188 ret = clk_prepare_enable(pit_clk);
189 if (ret)
190 return ret;
191
192 clk_rate = clk_get_rate(pit_clk);
193 cycle_per_jiffy = clk_rate / (HZ);
194
195 /* enable the pit module */
196 __raw_writel(~PITMCR_MDIS, timer_base + PITMCR);
197
198 ret = pit_clocksource_init(clk_rate);
199 if (ret)
200 return ret;
201
202 return pit_clockevent_init(clk_rate, irq);
203}
204CLOCKSOURCE_OF_DECLARE(vf610, "fsl,vf610-pit", pit_timer_init);