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/*
* linux/arch/arm/mach-nomadik/timer.c
*
* Copyright (C) 2008 STMicroelectronics
* Copyright (C) 2010 Alessandro Rubini
*
* 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/interrupt.h>
#include <linux/irq.h>
#include <linux/io.h>
#include <linux/clockchips.h>
#include <linux/jiffies.h>
#include <asm/mach/time.h>
#include <plat/mtu.h>
void __iomem *mtu_base; /* ssigned by machine code */
/*
* Kernel assumes that sched_clock can be called early
* but the MTU may not yet be initialized.
*/
static cycle_t nmdk_read_timer_dummy(struct clocksource *cs)
{
return 0;
}
/* clocksource: MTU decrements, so we negate the value being read. */
static cycle_t nmdk_read_timer(struct clocksource *cs)
{
return -readl(mtu_base + MTU_VAL(0));
}
static struct clocksource nmdk_clksrc = {
.name = "mtu_0",
.rating = 200,
.read = nmdk_read_timer_dummy,
.mask = CLOCKSOURCE_MASK(32),
.shift = 20,
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
/*
* Override the global weak sched_clock symbol with this
* local implementation which uses the clocksource to get some
* better resolution when scheduling the kernel. We accept that
* this wraps around for now, since it is just a relative time
* stamp. (Inspired by OMAP implementation.)
*/
unsigned long long notrace sched_clock(void)
{
return clocksource_cyc2ns(nmdk_clksrc.read(
&nmdk_clksrc),
nmdk_clksrc.mult,
nmdk_clksrc.shift);
}
/* Clockevent device: use one-shot mode */
static void nmdk_clkevt_mode(enum clock_event_mode mode,
struct clock_event_device *dev)
{
u32 cr;
switch (mode) {
case CLOCK_EVT_MODE_PERIODIC:
pr_err("%s: periodic mode not supported\n", __func__);
break;
case CLOCK_EVT_MODE_ONESHOT:
/* Load highest value, enable device, enable interrupts */
cr = readl(mtu_base + MTU_CR(1));
writel(0, mtu_base + MTU_LR(1));
writel(cr | MTU_CRn_ENA, mtu_base + MTU_CR(1));
writel(0x2, mtu_base + MTU_IMSC);
break;
case CLOCK_EVT_MODE_SHUTDOWN:
case CLOCK_EVT_MODE_UNUSED:
/* disable irq */
writel(0, mtu_base + MTU_IMSC);
break;
case CLOCK_EVT_MODE_RESUME:
break;
}
}
static int nmdk_clkevt_next(unsigned long evt, struct clock_event_device *ev)
{
/* writing the value has immediate effect */
writel(evt, mtu_base + MTU_LR(1));
return 0;
}
static struct clock_event_device nmdk_clkevt = {
.name = "mtu_1",
.features = CLOCK_EVT_FEAT_ONESHOT,
.shift = 32,
.rating = 200,
.set_mode = nmdk_clkevt_mode,
.set_next_event = nmdk_clkevt_next,
};
/*
* IRQ Handler for timer 1 of the MTU block.
*/
static irqreturn_t nmdk_timer_interrupt(int irq, void *dev_id)
{
struct clock_event_device *evdev = dev_id;
writel(1 << 1, mtu_base + MTU_ICR); /* Interrupt clear reg */
evdev->event_handler(evdev);
return IRQ_HANDLED;
}
static struct irqaction nmdk_timer_irq = {
.name = "Nomadik Timer Tick",
.flags = IRQF_DISABLED | IRQF_TIMER,
.handler = nmdk_timer_interrupt,
.dev_id = &nmdk_clkevt,
};
void __init nmdk_timer_init(void)
{
unsigned long rate;
u32 cr = MTU_CRn_32BITS;;
/*
* Tick rate is 2.4MHz for Nomadik and 110MHz for ux500:
* use a divide-by-16 counter if it's more than 16MHz
*/
rate = CLOCK_TICK_RATE;
if (rate > 16 << 20) {
rate /= 16;
cr |= MTU_CRn_PRESCALE_16;
} else {
cr |= MTU_CRn_PRESCALE_1;
}
/* Timer 0 is the free running clocksource */
writel(cr, mtu_base + MTU_CR(0));
writel(0, mtu_base + MTU_LR(0));
writel(0, mtu_base + MTU_BGLR(0));
writel(cr | MTU_CRn_ENA, mtu_base + MTU_CR(0));
nmdk_clksrc.mult = clocksource_hz2mult(rate, nmdk_clksrc.shift);
/* Now the scheduling clock is ready */
nmdk_clksrc.read = nmdk_read_timer;
if (clocksource_register(&nmdk_clksrc))
pr_err("timer: failed to initialize clock source %s\n",
nmdk_clksrc.name);
/* Timer 1 is used for events, fix according to rate */
writel(cr | MTU_CRn_ONESHOT, mtu_base + MTU_CR(1)); /* off, currently */
nmdk_clkevt.mult = div_sc(rate, NSEC_PER_SEC, nmdk_clkevt.shift);
nmdk_clkevt.max_delta_ns =
clockevent_delta2ns(0xffffffff, &nmdk_clkevt);
nmdk_clkevt.min_delta_ns =
clockevent_delta2ns(0x00000002, &nmdk_clkevt);
nmdk_clkevt.cpumask = cpumask_of(0);
/* Register irq and clockevents */
setup_irq(IRQ_MTU0, &nmdk_timer_irq);
clockevents_register_device(&nmdk_clkevt);
}
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