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 <blogic@openwrt.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 void systick_set_clock_mode(enum clock_event_mode mode,
40 struct clock_event_device *evt);
41
systick_next_event(unsigned long delta,struct clock_event_device * evt)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 + delta, sdev->membase + SYSTICK_COMPARE);
52
53 return 0;
54 }
55
systick_event_handler(struct clock_event_device * dev)56 static void systick_event_handler(struct clock_event_device *dev)
57 {
58 /* noting to do here */
59 }
60
systick_interrupt(int irq,void * dev_id)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_mode = systick_set_clock_mode,
80 .event_handler = systick_event_handler,
81 },
82 };
83
84 static struct irqaction systick_irqaction = {
85 .handler = systick_interrupt,
86 .flags = IRQF_PERCPU | IRQF_TIMER,
87 .dev_id = &systick.dev,
88 };
89
systick_set_clock_mode(enum clock_event_mode mode,struct clock_event_device * evt)90 static void systick_set_clock_mode(enum clock_event_mode mode,
91 struct clock_event_device *evt)
92 {
93 struct systick_device *sdev;
94
95 sdev = container_of(evt, struct systick_device, dev);
96
97 switch (mode) {
98 case CLOCK_EVT_MODE_ONESHOT:
99 if (!sdev->irq_requested)
100 setup_irq(systick.dev.irq, &systick_irqaction);
101 sdev->irq_requested = 1;
102 iowrite32(CFG_EXT_STK_EN | CFG_CNT_EN,
103 systick.membase + SYSTICK_CONFIG);
104 break;
105
106 case CLOCK_EVT_MODE_SHUTDOWN:
107 if (sdev->irq_requested)
108 free_irq(systick.dev.irq, &systick_irqaction);
109 sdev->irq_requested = 0;
110 iowrite32(0, systick.membase + SYSTICK_CONFIG);
111 break;
112
113 default:
114 pr_err("%s: Unhandeled mips clock_mode\n", systick.dev.name);
115 break;
116 }
117 }
118
ralink_systick_init(struct device_node * np)119 static void __init ralink_systick_init(struct device_node *np)
120 {
121 systick.membase = of_iomap(np, 0);
122 if (!systick.membase)
123 return;
124
125 systick_irqaction.name = np->name;
126 systick.dev.name = np->name;
127 clockevents_calc_mult_shift(&systick.dev, SYSTICK_FREQ, 60);
128 systick.dev.max_delta_ns = clockevent_delta2ns(0x7fff, &systick.dev);
129 systick.dev.min_delta_ns = clockevent_delta2ns(0x3, &systick.dev);
130 systick.dev.irq = irq_of_parse_and_map(np, 0);
131 if (!systick.dev.irq) {
132 pr_err("%s: request_irq failed", np->name);
133 return;
134 }
135
136 clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name,
137 SYSTICK_FREQ, 301, 16, clocksource_mmio_readl_up);
138
139 clockevents_register_device(&systick.dev);
140
141 pr_info("%s: running - mult: %d, shift: %d\n",
142 np->name, systick.dev.mult, systick.dev.shift);
143 }
144
145 CLOCKSOURCE_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init);
146