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/*
* OpenRISC time.c
*
* Linux architectural port borrowing liberally from similar works of
* others. All original copyrights apply as per the original source
* declaration.
*
* Modifications for the OpenRISC architecture:
* Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/interrupt.h>
#include <linux/ftrace.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/irq.h>
#include <linux/io.h>
#include <asm/cpuinfo.h>
static int openrisc_timer_set_next_event(unsigned long delta,
struct clock_event_device *dev)
{
u32 c;
/* Read 32-bit counter value, add delta, mask off the low 28 bits.
* We're guaranteed delta won't be bigger than 28 bits because the
* generic timekeeping code ensures that for us.
*/
c = mfspr(SPR_TTCR);
c += delta;
c &= SPR_TTMR_TP;
/* Set counter and enable interrupt.
* Keep timer in continuous mode always.
*/
mtspr(SPR_TTMR, SPR_TTMR_CR | SPR_TTMR_IE | c);
return 0;
}
/* This is the clock event device based on the OR1K tick timer.
* As the timer is being used as a continuous clock-source (required for HR
* timers) we cannot enable the PERIODIC feature. The tick timer can run using
* one-shot events, so no problem.
*/
static struct clock_event_device clockevent_openrisc_timer = {
.name = "openrisc_timer_clockevent",
.features = CLOCK_EVT_FEAT_ONESHOT,
.rating = 300,
.set_next_event = openrisc_timer_set_next_event,
};
static inline void timer_ack(void)
{
/* Clear the IP bit and disable further interrupts */
/* This can be done very simply... we just need to keep the timer
running, so just maintain the CR bits while clearing the rest
of the register
*/
mtspr(SPR_TTMR, SPR_TTMR_CR);
}
/*
* The timer interrupt is mostly handled in generic code nowadays... this
* function just acknowledges the interrupt and fires the event handler that
* has been set on the clockevent device by the generic time management code.
*
* This function needs to be called by the timer exception handler and that's
* all the exception handler needs to do.
*/
irqreturn_t __irq_entry timer_interrupt(struct pt_regs *regs)
{
struct pt_regs *old_regs = set_irq_regs(regs);
struct clock_event_device *evt = &clockevent_openrisc_timer;
timer_ack();
/*
* update_process_times() expects us to have called irq_enter().
*/
irq_enter();
evt->event_handler(evt);
irq_exit();
set_irq_regs(old_regs);
return IRQ_HANDLED;
}
static __init void openrisc_clockevent_init(void)
{
clockevent_openrisc_timer.cpumask = cpumask_of(0);
/* We only have 28 bits */
clockevents_config_and_register(&clockevent_openrisc_timer,
cpuinfo.clock_frequency,
100, 0x0fffffff);
}
/**
* Clocksource: Based on OpenRISC timer/counter
*
* This sets up the OpenRISC Tick Timer as a clock source. The tick timer
* is 32 bits wide and runs at the CPU clock frequency.
*/
static u64 openrisc_timer_read(struct clocksource *cs)
{
return (u64) mfspr(SPR_TTCR);
}
static struct clocksource openrisc_timer = {
.name = "openrisc_timer",
.rating = 200,
.read = openrisc_timer_read,
.mask = CLOCKSOURCE_MASK(32),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
static int __init openrisc_timer_init(void)
{
if (clocksource_register_hz(&openrisc_timer, cpuinfo.clock_frequency))
panic("failed to register clocksource");
/* Enable the incrementer: 'continuous' mode with interrupt disabled */
mtspr(SPR_TTMR, SPR_TTMR_CR);
return 0;
}
void __init time_init(void)
{
u32 upr;
upr = mfspr(SPR_UPR);
if (!(upr & SPR_UPR_TTP))
panic("Linux not supported on devices without tick timer");
openrisc_timer_init();
openrisc_clockevent_init();
}
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