Subject: [RFC PATCH] clocksource: arm_arch_timer: disable the evtstrm via the cmdline

From: [email-masked] (Mark Rutland)
Date: Fri, 17 Jun 2016 15:36:10 +0100

On Fri, Jun 17, 2016 at 02:43:31PM +0100, Will Deacon wrote:
> Disabling the eventstream can be useful for debugging and development
> purposes and is currently controlled via a Kconfig option
> (CONFIG_ARM_ARCH_TIMER_EVTSTREAM). Whilst this does the trick, it's
> often desirable to toggle the feature on the command line, so this patch
> adds a "noevtstrm" command line option to do just that.

I think anything that allows for better debugging on a production
kernels is great, so FWIW:

Acked-by: Mark Rutland <[email-masked]>

We might want to drop something in Documentation/kernel-parameters.txt

Mark.

> 
> Signed-off-by: Will Deacon <[email-masked]>
> ---
> 
> Sending as an RFC because we might want to remove the Kconfig option
> altogether if we have this.
> 
>  drivers/clocksource/arm_arch_timer.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index 4814446a0024..f579c0da7423 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -79,6 +79,15 @@ static enum ppi_nr arch_timer_uses_ppi = VIRT_PPI;
>  static bool arch_timer_c3stop;
>  static bool arch_timer_mem_use_virtual;
>  
> +static bool evtstrm_disable;
> +
> +static int __init early_evtstrm_disable(char *buf)
> +{
> +	evtstrm_disable = true;
> +	return 0;
> +}
> +early_param("noevtstrm", early_evtstrm_disable);
> +
>  /*
>   * Architected system timer support.
>   */
> @@ -372,7 +381,7 @@ static int arch_timer_setup(struct clock_event_device *clk)
>  		enable_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI], 0);
>  
>  	arch_counter_set_user_access();
> -	if (IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM))
> +	if (IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM) && !evtstrm_disable)
>  		arch_timer_configure_evtstream();
>  
>  	return 0;
> -- 
> 2.1.4
> 
> 
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