Commit 06470651 authored by Mark Rutland's avatar Mark Rutland Committed by Thomas Gleixner
Browse files

clocksource: Add generic dummy timer driver 



Several architectures have a dummy timer driver tightly coupled with
their broadcast code to support machines without cpu-local timers (or
where there is a lack of driver support).

Since 12ad1000: "clockevents: Add generic timer broadcast function"
it's been possible to write broadcast-capable timer drivers decoupled
from the broadcast mechanism. We can use this functionality to implement
a generic dummy timer driver that can be shared by all architectures
with generic tick broadcast (ARCH_HAS_TICK_BROADCAST).

This patch implements a generic dummy timer using this facility.

[sboyd: Make percpu data static, use __this_cpu_ptr(), move to
        early_initcall to properly register on each CPU, only
	register if more than one CPU possible]

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
Acked-by: default avatarMarc Zyngier <marc.zyngier@arm.com&gt;,>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1370291642-13259-3-git-send-email-sboyd@codeaurora.org


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 70e5975d

drivers/clocksource/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -31,3 +31,4 @@ obj-$(CONFIG_VF_PIT_TIMER) += vf_pit_timer.o 


obj-$(CONFIG_ARM_ARCH_TIMER)		+= arm_arch_timer.o

obj-$(CONFIG_CLKSRC_METAG_GENERIC)	+= metag_generic.o

obj-$(CONFIG_ARCH_HAS_TICK_BROADCAST)	+= dummy_timer.o

drivers/clocksource/dummy_timer.c

0 → 100644
+69 −0
Original line number Diff line number Diff line 
/*

 *  linux/drivers/clocksource/dummy_timer.c

 *

 *  Copyright (C) 2013 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/clockchips.h>

#include <linux/cpu.h>

#include <linux/init.h>

#include <linux/percpu.h>

#include <linux/cpumask.h>



static DEFINE_PER_CPU(struct clock_event_device, dummy_timer_evt);



static void dummy_timer_set_mode(enum clock_event_mode mode,

			   struct clock_event_device *evt)

{

	/*

	 * Core clockevents code will call this when exchanging timer devices.

	 * We don't need to do anything here.

	 */

}



static void __cpuinit dummy_timer_setup(void)

{

	int cpu = smp_processor_id();

	struct clock_event_device *evt = __this_cpu_ptr(&dummy_timer_evt);



	evt->name	= "dummy_timer";

	evt->features	= CLOCK_EVT_FEAT_PERIODIC |

			  CLOCK_EVT_FEAT_ONESHOT |

			  CLOCK_EVT_FEAT_DUMMY;

	evt->rating	= 100;

	evt->set_mode	= dummy_timer_set_mode;

	evt->cpumask	= cpumask_of(cpu);



	clockevents_register_device(evt);

}



static int __cpuinit dummy_timer_cpu_notify(struct notifier_block *self,

				      unsigned long action, void *hcpu)

{

	if ((action & ~CPU_TASKS_FROZEN) == CPU_STARTING)

		dummy_timer_setup();



	return NOTIFY_OK;

}



static struct notifier_block dummy_timer_cpu_nb __cpuinitdata = {

	.notifier_call = dummy_timer_cpu_notify,

};



static int __init dummy_timer_register(void)

{

	int err = register_cpu_notifier(&dummy_timer_cpu_nb);

	if (err)

		return err;



	/* We won't get a call on the boot CPU, so register immediately */

	if (num_possible_cpus() > 1)

		dummy_timer_setup();



	return 0;

}

early_initcall(dummy_timer_register);

CRA Git | Maintained and supported by SUSTech CRA and CCSE