bcm2835_timer.c
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/*
* Copyright 2012 Simon Arlott
*
* 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.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/bitops.h>
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/interrupt.h>
#include <linux/irqreturn.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/of_platform.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/sched_clock.h>
#include <asm/irq.h>
#define REG_CONTROL 0x00
#define REG_COUNTER_LO 0x04
#define REG_COUNTER_HI 0x08
#define REG_COMPARE(n) (0x0c + (n) * 4)
#define MAX_TIMER 3
#define DEFAULT_TIMER 3
struct bcm2835_timer {
void __iomem *control;
void __iomem *compare;
int match_mask;
struct clock_event_device evt;
struct irqaction act;
};
static void __iomem *system_clock __read_mostly;
static u64 notrace bcm2835_sched_read(void)
{
return readl_relaxed(system_clock);
}
static int bcm2835_time_set_next_event(unsigned long event,
struct clock_event_device *evt_dev)
{
struct bcm2835_timer *timer = container_of(evt_dev,
struct bcm2835_timer, evt);
writel_relaxed(readl_relaxed(system_clock) + event,
timer->compare);
return 0;
}
static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
{
struct bcm2835_timer *timer = dev_id;
void (*event_handler)(struct clock_event_device *);
if (readl_relaxed(timer->control) & timer->match_mask) {
writel_relaxed(timer->match_mask, timer->control);
event_handler = ACCESS_ONCE(timer->evt.event_handler);
if (event_handler)
event_handler(&timer->evt);
return IRQ_HANDLED;
} else {
return IRQ_NONE;
}
}
static void __init bcm2835_timer_init(struct device_node *node)
{
void __iomem *base;
u32 freq;
int irq;
struct bcm2835_timer *timer;
base = of_iomap(node, 0);
if (!base)
panic("Can't remap registers");
if (of_property_read_u32(node, "clock-frequency", &freq))
panic("Can't read clock-frequency");
system_clock = base + REG_COUNTER_LO;
sched_clock_register(bcm2835_sched_read, 32, freq);
clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
freq, 300, 32, clocksource_mmio_readl_up);
irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
if (irq <= 0)
panic("Can't parse IRQ");
timer = kzalloc(sizeof(*timer), GFP_KERNEL);
if (!timer)
panic("Can't allocate timer struct\n");
timer->control = base + REG_CONTROL;
timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
timer->match_mask = BIT(DEFAULT_TIMER);
timer->evt.name = node->name;
timer->evt.rating = 300;
timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
timer->evt.set_next_event = bcm2835_time_set_next_event;
timer->evt.cpumask = cpumask_of(0);
timer->act.name = node->name;
timer->act.flags = IRQF_TIMER | IRQF_SHARED;
timer->act.dev_id = timer;
timer->act.handler = bcm2835_time_interrupt;
if (setup_irq(irq, &timer->act))
panic("Can't set up timer IRQ\n");
clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
pr_info("bcm2835: system timer (irq = %d)\n", irq);
}
CLOCKSOURCE_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
bcm2835_timer_init);