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
32struct systick_device {
33	void __iomem *membase;
34	struct clock_event_device dev;
35	int irq_requested;
36	int freq_scale;
37};
38
39static void systick_set_clock_mode(enum clock_event_mode mode,
40				struct clock_event_device *evt);
41
42static 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
56static void systick_event_handler(struct clock_event_device *dev)
57{
58	/* noting to do here */
59}
60
61static 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
70static 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
84static struct irqaction systick_irqaction = {
85	.handler = systick_interrupt,
86	.flags = IRQF_PERCPU | IRQF_TIMER,
87	.dev_id = &systick.dev,
88};
89
90static 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
119static 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
145CLOCKSOURCE_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init);
146