timer.c
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/*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published
* by the Free Software Foundation.
*
* Copyright (C) 2013 John Crispin <blogic@openwrt.org>
*/
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/timer.h>
#include <linux/of_gpio.h>
#include <linux/clk.h>
#include <asm/mach-ralink/ralink_regs.h>
#define TIMER_REG_TMRSTAT 0x00
#define TIMER_REG_TMR0LOAD 0x10
#define TIMER_REG_TMR0CTL 0x18
#define TMRSTAT_TMR0INT BIT(0)
#define TMR0CTL_ENABLE BIT(7)
#define TMR0CTL_MODE_PERIODIC BIT(4)
#define TMR0CTL_PRESCALER 1
#define TMR0CTL_PRESCALE_VAL (0xf - TMR0CTL_PRESCALER)
#define TMR0CTL_PRESCALE_DIV (65536 / BIT(TMR0CTL_PRESCALER))
struct rt_timer {
struct device *dev;
void __iomem *membase;
int irq;
unsigned long timer_freq;
unsigned long timer_div;
};
static inline void rt_timer_w32(struct rt_timer *rt, u8 reg, u32 val)
{
__raw_writel(val, rt->membase + reg);
}
static inline u32 rt_timer_r32(struct rt_timer *rt, u8 reg)
{
return __raw_readl(rt->membase + reg);
}
static irqreturn_t rt_timer_irq(int irq, void *_rt)
{
struct rt_timer *rt = (struct rt_timer *) _rt;
rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
rt_timer_w32(rt, TIMER_REG_TMRSTAT, TMRSTAT_TMR0INT);
return IRQ_HANDLED;
}
static int rt_timer_request(struct rt_timer *rt)
{
int err = request_irq(rt->irq, rt_timer_irq, IRQF_DISABLED,
dev_name(rt->dev), rt);
if (err) {
dev_err(rt->dev, "failed to request irq\n");
} else {
u32 t = TMR0CTL_MODE_PERIODIC | TMR0CTL_PRESCALE_VAL;
rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
}
return err;
}
static void rt_timer_free(struct rt_timer *rt)
{
free_irq(rt->irq, rt);
}
static int rt_timer_config(struct rt_timer *rt, unsigned long divisor)
{
if (rt->timer_freq < divisor)
rt->timer_div = rt->timer_freq;
else
rt->timer_div = divisor;
rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
return 0;
}
static int rt_timer_enable(struct rt_timer *rt)
{
u32 t;
rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
t = rt_timer_r32(rt, TIMER_REG_TMR0CTL);
t |= TMR0CTL_ENABLE;
rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
return 0;
}
static void rt_timer_disable(struct rt_timer *rt)
{
u32 t;
t = rt_timer_r32(rt, TIMER_REG_TMR0CTL);
t &= ~TMR0CTL_ENABLE;
rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
}
static int rt_timer_probe(struct platform_device *pdev)
{
struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
struct rt_timer *rt;
struct clk *clk;
rt = devm_kzalloc(&pdev->dev, sizeof(*rt), GFP_KERNEL);
if (!rt) {
dev_err(&pdev->dev, "failed to allocate memory\n");
return -ENOMEM;
}
rt->irq = platform_get_irq(pdev, 0);
if (!rt->irq) {
dev_err(&pdev->dev, "failed to load irq\n");
return -ENOENT;
}
rt->membase = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(rt->membase))
return PTR_ERR(rt->membase);
clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(clk)) {
dev_err(&pdev->dev, "failed get clock rate\n");
return PTR_ERR(clk);
}
rt->timer_freq = clk_get_rate(clk) / TMR0CTL_PRESCALE_DIV;
if (!rt->timer_freq)
return -EINVAL;
rt->dev = &pdev->dev;
platform_set_drvdata(pdev, rt);
rt_timer_request(rt);
rt_timer_config(rt, 2);
rt_timer_enable(rt);
dev_info(&pdev->dev, "maximum frequency is %luHz\n", rt->timer_freq);
return 0;
}
static int rt_timer_remove(struct platform_device *pdev)
{
struct rt_timer *rt = platform_get_drvdata(pdev);
rt_timer_disable(rt);
rt_timer_free(rt);
return 0;
}
static const struct of_device_id rt_timer_match[] = {
{ .compatible = "ralink,rt2880-timer" },
{},
};
MODULE_DEVICE_TABLE(of, rt_timer_match);
static struct platform_driver rt_timer_driver = {
.probe = rt_timer_probe,
.remove = rt_timer_remove,
.driver = {
.name = "rt-timer",
.owner = THIS_MODULE,
.of_match_table = rt_timer_match
},
};
module_platform_driver(rt_timer_driver);
MODULE_DESCRIPTION("Ralink RT2880 timer");
MODULE_AUTHOR("John Crispin <blogic@openwrt.org");
MODULE_LICENSE("GPL");