1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/kernel.h>
3 #include <linux/init.h>
4 #include <linux/clocksource.h>
5 #include <linux/clockchips.h>
6 #include <linux/sched_clock.h>
7 #include <linux/interrupt.h>
8 #include <linux/irq.h>
9 #include <linux/io.h>
10 #include <asm/mach/time.h>
11 #include "soc.h"
12
13 /*************************************************************************
14 * Timer handling for EP93xx
15 *************************************************************************
16 * The ep93xx has four internal timers. Timers 1, 2 (both 16 bit) and
17 * 3 (32 bit) count down at 508 kHz, are self-reloading, and can generate
18 * an interrupt on underflow. Timer 4 (40 bit) counts down at 983.04 kHz,
19 * is free-running, and can't generate interrupts.
20 *
21 * The 508 kHz timers are ideal for use for the timer interrupt, as the
22 * most common values of HZ divide 508 kHz nicely. We pick the 32 bit
23 * timer (timer 3) to get as long sleep intervals as possible when using
24 * CONFIG_NO_HZ.
25 *
26 * The higher clock rate of timer 4 makes it a better choice than the
27 * other timers for use as clock source and for sched_clock(), providing
28 * a stable 40 bit time base.
29 *************************************************************************
30 */
31 #define EP93XX_TIMER_REG(x) (EP93XX_TIMER_BASE + (x))
32 #define EP93XX_TIMER1_LOAD EP93XX_TIMER_REG(0x00)
33 #define EP93XX_TIMER1_VALUE EP93XX_TIMER_REG(0x04)
34 #define EP93XX_TIMER1_CONTROL EP93XX_TIMER_REG(0x08)
35 #define EP93XX_TIMER123_CONTROL_ENABLE (1 << 7)
36 #define EP93XX_TIMER123_CONTROL_MODE (1 << 6)
37 #define EP93XX_TIMER123_CONTROL_CLKSEL (1 << 3)
38 #define EP93XX_TIMER1_CLEAR EP93XX_TIMER_REG(0x0c)
39 #define EP93XX_TIMER2_LOAD EP93XX_TIMER_REG(0x20)
40 #define EP93XX_TIMER2_VALUE EP93XX_TIMER_REG(0x24)
41 #define EP93XX_TIMER2_CONTROL EP93XX_TIMER_REG(0x28)
42 #define EP93XX_TIMER2_CLEAR EP93XX_TIMER_REG(0x2c)
43 #define EP93XX_TIMER4_VALUE_LOW EP93XX_TIMER_REG(0x60)
44 #define EP93XX_TIMER4_VALUE_HIGH EP93XX_TIMER_REG(0x64)
45 #define EP93XX_TIMER4_VALUE_HIGH_ENABLE (1 << 8)
46 #define EP93XX_TIMER3_LOAD EP93XX_TIMER_REG(0x80)
47 #define EP93XX_TIMER3_VALUE EP93XX_TIMER_REG(0x84)
48 #define EP93XX_TIMER3_CONTROL EP93XX_TIMER_REG(0x88)
49 #define EP93XX_TIMER3_CLEAR EP93XX_TIMER_REG(0x8c)
50
51 #define EP93XX_TIMER123_RATE 508469
52 #define EP93XX_TIMER4_RATE 983040
53
54 static u64 notrace ep93xx_read_sched_clock(void)
55 {
56 u64 ret;
57
58 ret = readl(EP93XX_TIMER4_VALUE_LOW);
59 ret |= ((u64) (readl(EP93XX_TIMER4_VALUE_HIGH) & 0xff) << 32);
60 return ret;
61 }
62
63 u64 ep93xx_clocksource_read(struct clocksource *c)
64 {
65 u64 ret;
66
67 ret = readl(EP93XX_TIMER4_VALUE_LOW);
68 ret |= ((u64) (readl(EP93XX_TIMER4_VALUE_HIGH) & 0xff) << 32);
69 return (u64) ret;
70 }
71
72 static int ep93xx_clkevt_set_next_event(unsigned long next,
73 struct clock_event_device *evt)
74 {
75 /* Default mode: periodic, off, 508 kHz */
76 u32 tmode = EP93XX_TIMER123_CONTROL_MODE |
77 EP93XX_TIMER123_CONTROL_CLKSEL;
78
79 /* Clear timer */
80 writel(tmode, EP93XX_TIMER3_CONTROL);
81
82 /* Set next event */
83 writel(next, EP93XX_TIMER3_LOAD);
84 writel(tmode | EP93XX_TIMER123_CONTROL_ENABLE,
85 EP93XX_TIMER3_CONTROL);
86 return 0;
87 }
88
89
90 static int ep93xx_clkevt_shutdown(struct clock_event_device *evt)
91 {
92 /* Disable timer */
93 writel(0, EP93XX_TIMER3_CONTROL);
94
95 return 0;
96 }
97
98 static struct clock_event_device ep93xx_clockevent = {
99 .name = "timer1",
100 .features = CLOCK_EVT_FEAT_ONESHOT,
101 .set_state_shutdown = ep93xx_clkevt_shutdown,
102 .set_state_oneshot = ep93xx_clkevt_shutdown,
103 .tick_resume = ep93xx_clkevt_shutdown,
104 .set_next_event = ep93xx_clkevt_set_next_event,
105 .rating = 300,
106 };
107
108 static irqreturn_t ep93xx_timer_interrupt(int irq, void *dev_id)
109 {
110 struct clock_event_device *evt = dev_id;
111
112 /* Writing any value clears the timer interrupt */
113 writel(1, EP93XX_TIMER3_CLEAR);
114
115 evt->event_handler(evt);
116
117 return IRQ_HANDLED;
118 }
119
120 void __init ep93xx_timer_init(void)
121 {
122 int irq = IRQ_EP93XX_TIMER3;
123 unsigned long flags = IRQF_TIMER | IRQF_IRQPOLL;
124
125 /* Enable and register clocksource and sched_clock on timer 4 */
126 writel(EP93XX_TIMER4_VALUE_HIGH_ENABLE,
127 EP93XX_TIMER4_VALUE_HIGH);
128 clocksource_mmio_init(NULL, "timer4",
129 EP93XX_TIMER4_RATE, 200, 40,
130 ep93xx_clocksource_read);
131 sched_clock_register(ep93xx_read_sched_clock, 40,
132 EP93XX_TIMER4_RATE);
133
134 /* Set up clockevent on timer 3 */
135 if (request_irq(irq, ep93xx_timer_interrupt, flags, "ep93xx timer",
136 &ep93xx_clockevent))
137 pr_err("Failed to request irq %d (ep93xx timer)\n", irq);
138 clockevents_config_and_register(&ep93xx_clockevent,
139 EP93XX_TIMER123_RATE,
140 1,
141 0xffffffffU);
142 }
143
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