Re: [PATCHv7 02/11] clocksource: add generic dummy timer driver

[Daniel Lezcano <daniel.lezcano@linaro.org>]

On 06/03/2013 10:33 PM, Stephen Boyd wrote:
> From: Mark Rutland <mark.rutland@arm.com>
> 
> 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 12ad100046: "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.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Acked-by: Marc Zyngier <marc.zyngier@arm.com>,
> Cc: John Stultz <john.stultz@linaro.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> [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: Stephen Boyd <sboyd@codeaurora.org>
> ---

Except the missing first letter capitalization, in the patch description
'add' => 'Add'.

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

>  drivers/clocksource/Makefile      |  1 +
>  drivers/clocksource/dummy_timer.c | 69 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 70 insertions(+)
>  create mode 100644 drivers/clocksource/dummy_timer.c
> 
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 8d979c7..1a17d76 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -29,3 +29,4 @@ obj-$(CONFIG_CLKSRC_SAMSUNG_PWM)	+= samsung_pwm_timer.o
>  
>  obj-$(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
> diff --git a/drivers/clocksource/dummy_timer.c b/drivers/clocksource/dummy_timer.c
> new file mode 100644
> index 0000000..1f55f96
> --- /dev/null
> +++ b/drivers/clocksource/dummy_timer.c
> @@ -0,0 +1,69 @@
> +/*
> + *  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);
> 


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