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#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/io.h>
#include <asm/mach/time.h>
#include "soc.h"
/*************************************************************************
* Timer handling for EP93xx
*************************************************************************
* The ep93xx has four internal timers. Timers 1, 2 (both 16 bit) and
* 3 (32 bit) count down at 508 kHz, are self-reloading, and can generate
* an interrupt on underflow. Timer 4 (40 bit) counts down at 983.04 kHz,
* is free-running, and can't generate interrupts.
*
* The 508 kHz timers are ideal for use for the timer interrupt, as the
* most common values of HZ divide 508 kHz nicely. We pick one of the 16
* bit timers (timer 1) since we don't need more than 16 bits of reload
* value as long as HZ >= 8.
*
* The higher clock rate of timer 4 makes it a better choice than the
* other timers for use in gettimeoffset(), while the fact that it can't
* generate interrupts means we don't have to worry about not being able
* to use this timer for something else. We also use timer 4 for keeping
* track of lost jiffies.
*/
#define EP93XX_TIMER_REG(x) (EP93XX_TIMER_BASE + (x))
#define EP93XX_TIMER1_LOAD EP93XX_TIMER_REG(0x00)
#define EP93XX_TIMER1_VALUE EP93XX_TIMER_REG(0x04)
#define EP93XX_TIMER1_CONTROL EP93XX_TIMER_REG(0x08)
#define EP93XX_TIMER123_CONTROL_ENABLE (1 << 7)
#define EP93XX_TIMER123_CONTROL_MODE (1 << 6)
#define EP93XX_TIMER123_CONTROL_CLKSEL (1 << 3)
#define EP93XX_TIMER1_CLEAR EP93XX_TIMER_REG(0x0c)
#define EP93XX_TIMER2_LOAD EP93XX_TIMER_REG(0x20)
#define EP93XX_TIMER2_VALUE EP93XX_TIMER_REG(0x24)
#define EP93XX_TIMER2_CONTROL EP93XX_TIMER_REG(0x28)
#define EP93XX_TIMER2_CLEAR EP93XX_TIMER_REG(0x2c)
#define EP93XX_TIMER4_VALUE_LOW EP93XX_TIMER_REG(0x60)
#define EP93XX_TIMER4_VALUE_HIGH EP93XX_TIMER_REG(0x64)
#define EP93XX_TIMER4_VALUE_HIGH_ENABLE (1 << 8)
#define EP93XX_TIMER3_LOAD EP93XX_TIMER_REG(0x80)
#define EP93XX_TIMER3_VALUE EP93XX_TIMER_REG(0x84)
#define EP93XX_TIMER3_CONTROL EP93XX_TIMER_REG(0x88)
#define EP93XX_TIMER3_CLEAR EP93XX_TIMER_REG(0x8c)
#define EP93XX_TIMER123_CLOCK 508469
#define EP93XX_TIMER4_CLOCK 983040
#define TIMER1_RELOAD ((EP93XX_TIMER123_CLOCK / HZ) - 1)
#define TIMER4_TICKS_PER_JIFFY DIV_ROUND_CLOSEST(EP93XX_TIMER4_CLOCK, HZ)
static unsigned int last_jiffy_time;
static irqreturn_t ep93xx_timer_interrupt(int irq, void *dev_id)
{
/* Writing any value clears the timer interrupt */
__raw_writel(1, EP93XX_TIMER1_CLEAR);
/* Recover lost jiffies */
while ((signed long)
(__raw_readl(EP93XX_TIMER4_VALUE_LOW) - last_jiffy_time)
>= TIMER4_TICKS_PER_JIFFY) {
last_jiffy_time += TIMER4_TICKS_PER_JIFFY;
timer_tick();
}
return IRQ_HANDLED;
}
static struct irqaction ep93xx_timer_irq = {
.name = "ep93xx timer",
.flags = IRQF_TIMER | IRQF_IRQPOLL,
.handler = ep93xx_timer_interrupt,
};
static u32 ep93xx_gettimeoffset(void)
{
int offset;
offset = __raw_readl(EP93XX_TIMER4_VALUE_LOW) - last_jiffy_time;
/*
* Timer 4 is based on a 983.04 kHz reference clock,
* so dividing by 983040 gives the fraction of a second,
* so dividing by 0.983040 converts to uS.
* Refactor the calculation to avoid overflow.
* Finally, multiply by 1000 to give nS.
*/
return (offset + (53 * offset / 3072)) * 1000;
}
void __init ep93xx_timer_init(void)
{
u32 tmode = EP93XX_TIMER123_CONTROL_MODE |
EP93XX_TIMER123_CONTROL_CLKSEL;
arch_gettimeoffset = ep93xx_gettimeoffset;
/* Enable periodic HZ timer. */
__raw_writel(tmode, EP93XX_TIMER1_CONTROL);
__raw_writel(TIMER1_RELOAD, EP93XX_TIMER1_LOAD);
__raw_writel(tmode | EP93XX_TIMER123_CONTROL_ENABLE,
EP93XX_TIMER1_CONTROL);
/* Enable lost jiffy timer. */
__raw_writel(EP93XX_TIMER4_VALUE_HIGH_ENABLE,
EP93XX_TIMER4_VALUE_HIGH);
setup_irq(IRQ_EP93XX_TIMER1, &ep93xx_timer_irq);
}
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