ARM: bcm2835: add system timer

BCM2835 System Timer

The System Timer peripheral provides four 32-bit timer channels and a

single 64-bit free running counter. Each channel has an output compare

register, which is compared against the 32 least significant bits of the

free running counter values, and generates an interrupt.

Required properties:

- compatible : should be "brcm,bcm2835-system-timer.txt"

- reg : Specifies base physical address and size of the registers.

- interrupts : A list of 4 interrupt sinks; one per timer channel.

- clock-frequency : The frequency of the clock that drives the counter, in Hz.

Example:

timer {

	compatible = "brcm,bcm2835-system-timer";

	reg = <0x7e003000 0x1000>;

	interrupts = <1 0>, <1 1>, <1 2>, <1 3>;

	clock-frequency = <1000000>;

};

		#size-cells = <1>;

		ranges = <0x7e000000 0x20000000 0x02000000>;

		timer {

			compatible = "brcm,bcm2835-system-timer";

			reg = <0x7e003000 0x1000>;

			interrupts = <1 0>, <1 1>, <1 2>, <1 3>;

			clock-frequency = <1000000>;

		};

		intc: interrupt-controller {

			compatible = "brcm,bcm2835-armctrl-ic";

			reg = <0x7e00b200 0x200>;

#include <linux/init.h>

#include <linux/irqchip/bcm2835.h>

#include <linux/of_platform.h>

#include <linux/bcm2835_timer.h>

#include <asm/mach/arch.h>

#include <asm/mach/map.h>

#include <asm/mach/time.h>

#include <mach/bcm2835_soc.h>

	}

}

static void __init bcm2835_timer_init(void)

{

}

struct sys_timer bcm2835_timer = {

	.init = bcm2835_timer_init

};

static const char * const bcm2835_compat[] = {

	"brcm,bcm2835",

	NULL

obj-$(CONFIG_DW_APB_TIMER_OF)	+= dw_apb_timer_of.o

obj-$(CONFIG_CLKSRC_DBX500_PRCMU)	+= clksrc-dbx500-prcmu.o

obj-$(CONFIG_ARMADA_370_XP_TIMER)	+= time-armada-370-xp.o

obj-$(CONFIG_ARCH_BCM2835)	+= bcm2835_timer.o

/*

 * 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/bcm2835_timer.h>

#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 <asm/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 u32 notrace bcm2835_sched_read(void)

{

	return readl_relaxed(system_clock);

}

static void bcm2835_time_set_mode(enum clock_event_mode mode,

	struct clock_event_device *evt_dev)

{

	switch (mode) {

	case CLOCK_EVT_MODE_ONESHOT:

	case CLOCK_EVT_MODE_UNUSED:

	case CLOCK_EVT_MODE_SHUTDOWN:

	case CLOCK_EVT_MODE_RESUME:

		break;

	default:

		WARN(1, "%s: unhandled event mode %d\n", __func__, mode);

		break;

	}

}

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 struct of_device_id bcm2835_time_match[] __initconst = {

	{ .compatible = "brcm,bcm2835-system-timer" },

	{}

};

static void __init bcm2835_time_init(void)

{

	struct device_node *node;

	void __iomem *base;

	u32 freq;

	int irq;

	struct bcm2835_timer *timer;

	node = of_find_matching_node(NULL, bcm2835_time_match);

	if (!node)

		panic("No bcm2835 timer node");

	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;

	setup_sched_clock(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_mode = bcm2835_time_set_mode;

	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);

}

struct sys_timer bcm2835_timer = {

	.init = bcm2835_time_init,

};