Re: [PATCH] ARM: smp: Allow real broadcast device selection instead of always dummy

[Santosh Shilimkar <santosh.shilimkar@ti.com>]

(Forgot to CC Thomas)

On Wednesday 13 March 2013 02:36 PM, Santosh Shilimkar wrote:
> With recent arm broadcast time clean-up from Mark Rutland, the dummy
> broadcast device is always registered with timer subsystem. And since
> the rating of the dummy clock event is very high, it is preferred
> over a real broad-cast clock event.
> 
> This is a change in behavior from past and not an intended
> one. So reduce the rating of the dummy clockevent so that
> real broadcast device is selected when available.
> 
> Without this all the C states with C3STOP won't work since
> the broad cast notifier will take an abort.
> 
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Russell King <linux@arm.linux.org.uk>
> 
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
> ---
> Its a regression so hopefully can get into the 3.9-rcx. Noticed
> this one on A15 platform. A9 platform the issue may not be seen
> since the local timer check avoids dummy timer registration.
> 
Some one pointed me to a fix made by Mark which was discussed
under '[BUG] ARM Architected timers appear broken in 3.9-rc1' subject.
That patch seems to be more of work around since the root of the
problem is incorrect dummy timer rating. Either way, both patches
fix the issue.

>  arch/arm/kernel/smp.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index 31644f1..79078ed 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -480,7 +480,7 @@ static void __cpuinit broadcast_timer_setup(struct clock_event_device *evt)
>  	evt->features	= CLOCK_EVT_FEAT_ONESHOT |
>  			  CLOCK_EVT_FEAT_PERIODIC |
>  			  CLOCK_EVT_FEAT_DUMMY;
> -	evt->rating	= 400;
> +	evt->rating	= 100;
>  	evt->mult	= 1;
>  	evt->set_mode	= broadcast_timer_set_mode;
>  
>