1/*
2 * This program is free software; you can redistribute it and/or modify it
3 * under the terms of the GNU General Public License version 2 as published
4 * by the Free Software Foundation.
5 *
6 * Copyright (C) 2013 John Crispin <blogic@openwrt.org>
7*/
8
9#include <linux/module.h>
10#include <linux/platform_device.h>
11#include <linux/interrupt.h>
12#include <linux/timer.h>
13#include <linux/of_gpio.h>
14#include <linux/clk.h>
15
16#include <asm/mach-ralink/ralink_regs.h>
17
18#define TIMER_REG_TMRSTAT		0x00
19#define TIMER_REG_TMR0LOAD		0x10
20#define TIMER_REG_TMR0CTL		0x18
21
22#define TMRSTAT_TMR0INT			BIT(0)
23
24#define TMR0CTL_ENABLE			BIT(7)
25#define TMR0CTL_MODE_PERIODIC		BIT(4)
26#define TMR0CTL_PRESCALER		1
27#define TMR0CTL_PRESCALE_VAL		(0xf - TMR0CTL_PRESCALER)
28#define TMR0CTL_PRESCALE_DIV		(65536 / BIT(TMR0CTL_PRESCALER))
29
30struct rt_timer {
31	struct device	*dev;
32	void __iomem	*membase;
33	int		irq;
34	unsigned long	timer_freq;
35	unsigned long	timer_div;
36};
37
38static inline void rt_timer_w32(struct rt_timer *rt, u8 reg, u32 val)
39{
40	__raw_writel(val, rt->membase + reg);
41}
42
43static inline u32 rt_timer_r32(struct rt_timer *rt, u8 reg)
44{
45	return __raw_readl(rt->membase + reg);
46}
47
48static irqreturn_t rt_timer_irq(int irq, void *_rt)
49{
50	struct rt_timer *rt =  (struct rt_timer *) _rt;
51
52	rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
53	rt_timer_w32(rt, TIMER_REG_TMRSTAT, TMRSTAT_TMR0INT);
54
55	return IRQ_HANDLED;
56}
57
58
59static int rt_timer_request(struct rt_timer *rt)
60{
61	int err = request_irq(rt->irq, rt_timer_irq, 0,
62						dev_name(rt->dev), rt);
63	if (err) {
64		dev_err(rt->dev, "failed to request irq\n");
65	} else {
66		u32 t = TMR0CTL_MODE_PERIODIC | TMR0CTL_PRESCALE_VAL;
67		rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
68	}
69	return err;
70}
71
72static void rt_timer_free(struct rt_timer *rt)
73{
74	free_irq(rt->irq, rt);
75}
76
77static int rt_timer_config(struct rt_timer *rt, unsigned long divisor)
78{
79	if (rt->timer_freq < divisor)
80		rt->timer_div = rt->timer_freq;
81	else
82		rt->timer_div = divisor;
83
84	rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
85
86	return 0;
87}
88
89static int rt_timer_enable(struct rt_timer *rt)
90{
91	u32 t;
92
93	rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
94
95	t = rt_timer_r32(rt, TIMER_REG_TMR0CTL);
96	t |= TMR0CTL_ENABLE;
97	rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
98
99	return 0;
100}
101
102static void rt_timer_disable(struct rt_timer *rt)
103{
104	u32 t;
105
106	t = rt_timer_r32(rt, TIMER_REG_TMR0CTL);
107	t &= ~TMR0CTL_ENABLE;
108	rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
109}
110
111static int rt_timer_probe(struct platform_device *pdev)
112{
113	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
114	struct rt_timer *rt;
115	struct clk *clk;
116
117	rt = devm_kzalloc(&pdev->dev, sizeof(*rt), GFP_KERNEL);
118	if (!rt) {
119		dev_err(&pdev->dev, "failed to allocate memory\n");
120		return -ENOMEM;
121	}
122
123	rt->irq = platform_get_irq(pdev, 0);
124	if (!rt->irq) {
125		dev_err(&pdev->dev, "failed to load irq\n");
126		return -ENOENT;
127	}
128
129	rt->membase = devm_ioremap_resource(&pdev->dev, res);
130	if (IS_ERR(rt->membase))
131		return PTR_ERR(rt->membase);
132
133	clk = devm_clk_get(&pdev->dev, NULL);
134	if (IS_ERR(clk)) {
135		dev_err(&pdev->dev, "failed get clock rate\n");
136		return PTR_ERR(clk);
137	}
138
139	rt->timer_freq = clk_get_rate(clk) / TMR0CTL_PRESCALE_DIV;
140	if (!rt->timer_freq)
141		return -EINVAL;
142
143	rt->dev = &pdev->dev;
144	platform_set_drvdata(pdev, rt);
145
146	rt_timer_request(rt);
147	rt_timer_config(rt, 2);
148	rt_timer_enable(rt);
149
150	dev_info(&pdev->dev, "maximum frequency is %luHz\n", rt->timer_freq);
151
152	return 0;
153}
154
155static int rt_timer_remove(struct platform_device *pdev)
156{
157	struct rt_timer *rt = platform_get_drvdata(pdev);
158
159	rt_timer_disable(rt);
160	rt_timer_free(rt);
161
162	return 0;
163}
164
165static const struct of_device_id rt_timer_match[] = {
166	{ .compatible = "ralink,rt2880-timer" },
167	{},
168};
169MODULE_DEVICE_TABLE(of, rt_timer_match);
170
171static struct platform_driver rt_timer_driver = {
172	.probe = rt_timer_probe,
173	.remove = rt_timer_remove,
174	.driver = {
175		.name		= "rt-timer",
176		.of_match_table	= rt_timer_match
177	},
178};
179
180module_platform_driver(rt_timer_driver);
181
182MODULE_DESCRIPTION("Ralink RT2880 timer");
183MODULE_AUTHOR("John Crispin <blogic@openwrt.org");
184MODULE_LICENSE("GPL");
185