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