1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Ralink System Tick Counter driver present on RT3352 and MT7620 SoCs.
4 *
5 * Copyright (C) 2013 by John Crispin <john@phrozen.org>
6 */
7
8#include <linux/clockchips.h>
9#include <linux/clocksource.h>
10#include <linux/interrupt.h>
11#include <linux/reset.h>
12#include <linux/init.h>
13#include <linux/time.h>
14#include <linux/of.h>
15#include <linux/of_irq.h>
16#include <linux/of_address.h>
17
18#define SYSTICK_FREQ (50 * 1000)
19
20#define SYSTICK_CONFIG 0x00
21#define SYSTICK_COMPARE 0x04
22#define SYSTICK_COUNT 0x08
23
24/* route systick irq to mips irq 7 instead of the r4k-timer */
25#define CFG_EXT_STK_EN 0x2
26/* enable the counter */
27#define CFG_CNT_EN 0x1
28
29struct systick_device {
30 void __iomem *membase;
31 struct clock_event_device dev;
32 int irq_requested;
33 int freq_scale;
34};
35
36static int systick_set_oneshot(struct clock_event_device *evt);
37static int systick_shutdown(struct clock_event_device *evt);
38
39static int systick_next_event(unsigned long delta,
40 struct clock_event_device *evt)
41{
42 struct systick_device *sdev;
43 u32 count;
44
45 sdev = container_of(evt, struct systick_device, dev);
46 count = ioread32(sdev->membase + SYSTICK_COUNT);
47 count = (count + delta) % SYSTICK_FREQ;
48 iowrite32(count, sdev->membase + SYSTICK_COMPARE);
49
50 return 0;
51}
52
53static void systick_event_handler(struct clock_event_device *dev)
54{
55 /* noting to do here */
56}
57
58static irqreturn_t systick_interrupt(int irq, void *dev_id)
59{
60 struct clock_event_device *dev = (struct clock_event_device *)dev_id;
61
62 dev->event_handler(dev);
63
64 return IRQ_HANDLED;
65}
66
67static struct systick_device systick = {
68 .dev = {
69 /*
70 * cevt-r4k uses 300, make sure systick
71 * gets used if available
72 */
73 .rating = 310,
74 .features = CLOCK_EVT_FEAT_ONESHOT,
75 .set_next_event = systick_next_event,
76 .set_state_shutdown = systick_shutdown,
77 .set_state_oneshot = systick_set_oneshot,
78 .event_handler = systick_event_handler,
79 },
80};
81
82static int systick_shutdown(struct clock_event_device *evt)
83{
84 struct systick_device *sdev;
85
86 sdev = container_of(evt, struct systick_device, dev);
87
88 if (sdev->irq_requested)
89 free_irq(systick.dev.irq, &systick.dev);
90 sdev->irq_requested = 0;
91 iowrite32(0, systick.membase + SYSTICK_CONFIG);
92
93 return 0;
94}
95
96static int systick_set_oneshot(struct clock_event_device *evt)
97{
98 const char *name = systick.dev.name;
99 struct systick_device *sdev;
100 int irq = systick.dev.irq;
101
102 sdev = container_of(evt, struct systick_device, dev);
103
104 if (!sdev->irq_requested) {
105 if (request_irq(irq, handler: systick_interrupt,
106 IRQF_PERCPU | IRQF_TIMER, name, dev: &systick.dev))
107 pr_err("Failed to request irq %d (%s)\n", irq, name);
108 }
109 sdev->irq_requested = 1;
110 iowrite32(CFG_EXT_STK_EN | CFG_CNT_EN,
111 systick.membase + SYSTICK_CONFIG);
112
113 return 0;
114}
115
116static int __init ralink_systick_init(struct device_node *np)
117{
118 int ret;
119
120 systick.membase = of_iomap(node: np, index: 0);
121 if (!systick.membase)
122 return -ENXIO;
123
124 systick.dev.name = np->name;
125 clockevents_calc_mult_shift(ce: &systick.dev, SYSTICK_FREQ, maxsec: 60);
126 systick.dev.max_delta_ns = clockevent_delta2ns(latch: 0x7fff, evt: &systick.dev);
127 systick.dev.max_delta_ticks = 0x7fff;
128 systick.dev.min_delta_ns = clockevent_delta2ns(latch: 0x3, evt: &systick.dev);
129 systick.dev.min_delta_ticks = 0x3;
130 systick.dev.irq = irq_of_parse_and_map(node: np, index: 0);
131 if (!systick.dev.irq) {
132 pr_err("%pOFn: request_irq failed", np);
133 ret = -EINVAL;
134 goto err_iounmap;
135 }
136
137 ret = clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name,
138 SYSTICK_FREQ, 301, 16,
139 clocksource_mmio_readl_up);
140 if (ret)
141 goto err_free_irq;
142
143 clockevents_register_device(dev: &systick.dev);
144
145 pr_info("%pOFn: running - mult: %d, shift: %d\n",
146 np, systick.dev.mult, systick.dev.shift);
147
148 return 0;
149
150err_free_irq:
151 irq_dispose_mapping(virq: systick.dev.irq);
152err_iounmap:
153 iounmap(addr: systick.membase);
154 return ret;
155}
156
157TIMER_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init);
158

source code of linux/drivers/clocksource/timer-ralink.c