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/*
* linux/arch/arm/kernel/smp_twd.c
*
* Copyright (C) 2002 ARM Ltd.
* 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.
*/
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/smp.h>
#include <linux/jiffies.h>
#include <linux/clockchips.h>
#include <linux/irq.h>
#include <linux/io.h>
#include <asm/smp_twd.h>
#include <asm/hardware/gic.h>
/* set up by the platform code */
void __iomem *twd_base;
static unsigned long twd_timer_rate;
static void twd_set_mode(enum clock_event_mode mode,
struct clock_event_device *clk)
{
unsigned long ctrl;
switch (mode) {
case CLOCK_EVT_MODE_PERIODIC:
/* timer load already set up */
ctrl = TWD_TIMER_CONTROL_ENABLE | TWD_TIMER_CONTROL_IT_ENABLE
| TWD_TIMER_CONTROL_PERIODIC;
__raw_writel(twd_timer_rate / HZ, twd_base + TWD_TIMER_LOAD);
break;
case CLOCK_EVT_MODE_ONESHOT:
/* period set, and timer enabled in 'next_event' hook */
ctrl = TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT;
break;
case CLOCK_EVT_MODE_UNUSED:
case CLOCK_EVT_MODE_SHUTDOWN:
default:
ctrl = 0;
}
__raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
}
static int twd_set_next_event(unsigned long evt,
struct clock_event_device *unused)
{
unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL);
ctrl |= TWD_TIMER_CONTROL_ENABLE;
__raw_writel(evt, twd_base + TWD_TIMER_COUNTER);
__raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
return 0;
}
/*
* local_timer_ack: checks for a local timer interrupt.
*
* If a local timer interrupt has occurred, acknowledge and return 1.
* Otherwise, return 0.
*/
int twd_timer_ack(void)
{
if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) {
__raw_writel(1, twd_base + TWD_TIMER_INTSTAT);
return 1;
}
return 0;
}
static void __cpuinit twd_calibrate_rate(void)
{
unsigned long count;
u64 waitjiffies;
/*
* If this is the first time round, we need to work out how fast
* the timer ticks
*/
if (twd_timer_rate == 0) {
printk(KERN_INFO "Calibrating local timer... ");
/* Wait for a tick to start */
waitjiffies = get_jiffies_64() + 1;
while (get_jiffies_64() < waitjiffies)
udelay(10);
/* OK, now the tick has started, let's get the timer going */
waitjiffies += 5;
/* enable, no interrupt or reload */
__raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
/* maximum value */
__raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
while (get_jiffies_64() < waitjiffies)
udelay(10);
count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
(twd_timer_rate / 1000000) % 100);
}
}
/*
* Setup the local clock events for a CPU.
*/
void __cpuinit twd_timer_setup(struct clock_event_device *clk)
{
twd_calibrate_rate();
clk->name = "local_timer";
clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
CLOCK_EVT_FEAT_C3STOP;
clk->rating = 350;
clk->set_mode = twd_set_mode;
clk->set_next_event = twd_set_next_event;
clk->shift = 20;
clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift);
clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
/* Make sure our local interrupt controller has this enabled */
gic_enable_ppi(clk->irq);
clockevents_register_device(clk);
}
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