/*
* System Timer Interrupt reconfigured to run in free-run mode.
* Author: Vitaly Wool
* Copyright 2004 MontaVista Software Inc.
* Copyright 2004-2007 Freescale Semiconductor, Inc. All Rights Reserved.
*/
/*
* 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.
*/
/*!
* @file time.c
* @brief This file contains OS tick and wdog timer implementations.
*
* This file contains OS tick and wdog timer implementations.
*
* @ingroup Timers
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <asm/hardware.h>
#include <asm/mach/time.h>
#include <asm/io.h>
#include <asm/arch/common.h>
/*!
* This is the timer interrupt service routine to do required tasks.
* It also services the WDOG timer at the frequency of twice per WDOG
* timeout value. For example, if the WDOG's timeout value is 4 (2
* seconds since the WDOG runs at 0.5Hz), it will be serviced once
* every 2/2=1 second.
*
* @param irq GPT interrupt source number (not used)
* @param dev_id this parameter is not used
* @return always returns \b IRQ_HANDLED as defined in
* include/linux/interrupt.h.
*/
static irqreturn_t mxc_timer_interrupt(int irq, void *dev_id)
{
unsigned int next_match;
write_seqlock(&xtime_lock);
if (__raw_readl(MXC_GPT_GPTSR) & GPTSR_OF1) {
do {
timer_tick();
next_match = __raw_readl(MXC_GPT_GPTOCR1) + LATCH;
__raw_writel(GPTSR_OF1, MXC_GPT_GPTSR);
__raw_writel(next_match, MXC_GPT_GPTOCR1);
} while ((signed long)(next_match -
__raw_readl(MXC_GPT_GPTCNT)) <= 0);
}
write_sequnlock(&xtime_lock);
return IRQ_HANDLED;
}
/*!
* This function is used to obtain the number of microseconds since the last
* timer interrupt. Note that interrupts is disabled by do_gettimeofday().
*
* @return the number of microseconds since the last timer interrupt.
*/
static unsigned long mxc_gettimeoffset(void)
{
unsigned long ticks_to_match, elapsed, usec, tick_usec, i;
/* Get ticks before next timer match */
ticks_to_match =
__raw_readl(MXC_GPT_GPTOCR1) - __raw_readl(MXC_GPT_GPTCNT);
/* We need elapsed ticks since last match */
elapsed = LATCH - ticks_to_match;
/* Now convert them to usec */
/* Insure no overflow when calculating the usec below */
for (i = 1, tick_usec = tick_nsec / 1000;; i *= 2) {
tick_usec /= i;
if ((0xFFFFFFFF / tick_usec) > elapsed)
break;
}
usec = (unsigned long)(elapsed * tick_usec) / (LATCH / i);
return usec;
}
/*!
* The OS tick timer interrupt structure.
*/
static struct irqaction timer_irq = {
.name = "MXC Timer Tick",
.flags = IRQF_DISABLED | IRQF_TIMER,
.handler = mxc_timer_interrupt
};
/*!
* This function is used to initialize the GPT to produce an interrupt
* based on HZ. It is called by start_kernel() during system startup.
*/
void __init mxc_init_time(void)
{
u32 reg, v;
reg = __raw_readl(MXC_GPT_GPTCR);
reg &= ~GPTCR_ENABLE;
__raw_writel(reg, MXC_GPT_GPTCR);
reg |= GPTCR_SWR;
__raw_writel(reg, MXC_GPT_GPTCR);
while ((__raw_readl(MXC_GPT_GPTCR) & GPTCR_SWR) != 0)
cpu_relax();
reg = GPTCR_FRR | GPTCR_CLKSRC_HIGHFREQ;
__raw_writel(reg, MXC_GPT_GPTCR);
/* TODO: get timer rate from clk driver */
v = 66500000;
__raw_writel((v / CLOCK_TICK_RATE) - 1, MXC_GPT_GPTPR);
if ((v % CLOCK_TICK_RATE) != 0) {
pr_info("\nWARNING: Can't generate CLOCK_TICK_RATE at %d Hz\n",
CLOCK_TICK_RATE);
}
pr_info("Actual CLOCK_TICK_RATE is %d Hz\n",
v / ((__raw_readl(MXC_GPT_GPTPR) & 0xFFF) + 1));
reg = __raw_readl(MXC_GPT_GPTCNT);
reg += LATCH;
__raw_writel(reg, MXC_GPT_GPTOCR1);
setup_irq(MXC_INT_GPT, &timer_irq);
reg = __raw_readl(MXC_GPT_GPTCR);
reg =
GPTCR_FRR | GPTCR_CLKSRC_HIGHFREQ | GPTCR_STOPEN | GPTCR_DOZEN |
GPTCR_WAITEN | GPTCR_ENMOD | GPTCR_ENABLE;
__raw_writel(reg, MXC_GPT_GPTCR);
__raw_writel(GPTIR_OF1IE, MXC_GPT_GPTIR);
}
struct sys_timer mxc_timer = {
.init = mxc_init_time,
.offset = mxc_gettimeoffset,
};
