Re: [PATCH] clocksource: timer-atmel-pit: don't suspend/resume if unused

[Daniel Lezcano]

On 01/12/2015 03:04 PM, Nicolas Ferre wrote:
> Le 18/12/2014 15:05, Nicolas Ferre a Ãcrit :
> > From: Sylvain Rochet <sylvain.rochet@xxxxxxxxxxxx>
> >
> > Waiting for PIT to stop counting takes a long time:
> >    1/(Master clock/prescaler/PIVR)
> > = 1/(133 MHz     /16       /2^20)
> > = 126 ms
> >
> > Up to 126 ms if master clock is set to 133 MHz, skipping suspend/resume
> > of the unused PIT device reduce (suspend time + resume time) from ~140 ms
> > to ~17 ms.
> >
> > Signed-off-by: Sylvain Rochet <sylvain.rochet@xxxxxxxxxxxx>
> > [nicolas.ferre@xxxxxxxxx: move to newer clocksource driver]
> > Signed-off-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxx>
> > Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> > ---
> > Hi Sylvain,
> >
> > I re-worked (and "Acked") your patch so it can be applied on the newer Mainline
> > kernels. Beware, I changed the "subject line" as well. The PIT driver moved
> > recently (3.18).
> >
> > Daniel,
> > Can you take this patch in your tree?
>
> Hi Daniel,
>
> Anything prevents this patch from being merged (aka ping ;-))?

[Cc'ed tglx].

Hi Nico,

thanks for the head up.

Nothing prevents it but I am wondering if this change shouldn't be in 
the generic framework (kernel/time/clocksource.c and 
kernel/time/clockevents.c), so all drivers will benefit this change ?


> > Thanks, bye.
> >    Nicolas.
> >
> >   drivers/clocksource/timer-atmel-pit.c | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/clocksource/timer-atmel-pit.c b/drivers/clocksource/timer-atmel-pit.c
> > index b5b4d4585c9a..5408bc7c68d8 100644
> > --- a/drivers/clocksource/timer-atmel-pit.c
> > +++ b/drivers/clocksource/timer-atmel-pit.c
> > @@ -123,6 +123,10 @@ static void at91sam926x_pit_suspend(struct clock_event_device *cedev)
> >   {
> >   	struct pit_data *data = clkevt_to_pit_data(cedev);
> >
> > +	/* Don't suspend PIT if unused */
> > +	if (cedev->mode == CLOCK_EVT_MODE_UNUSED)
> > +		return;
> > +
> >   	/* Disable timer */
> >   	pit_write(data->base, AT91_PIT_MR, 0);
> >   }
> > @@ -145,6 +149,10 @@ static void at91sam926x_pit_resume(struct clock_event_device *cedev)
> >   {
> >   	struct pit_data *data = clkevt_to_pit_data(cedev);
> >
> > +	/* Don't resume PIT if unused */
> > +	if (cedev->mode == CLOCK_EVT_MODE_UNUSED)
> > +		return;
> > +
> >   	at91sam926x_pit_reset(data);
> >   }


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