[PATCH] ARM: at91/pit: don't suspend/resume if unused

[PATCH] ARM: at91/pit: don't suspend/resume if unused

[Sylvain Rochet]

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@finsecur.com>
---
 arch/arm/mach-at91/at91sam926x_time.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm/mach-at91/at91sam926x_time.c b/arch/arm/mach-at91/at91sam926x_time.c
index e3344b4..44526aa 100644
--- a/arch/arm/mach-at91/at91sam926x_time.c
+++ b/arch/arm/mach-at91/at91sam926x_time.c
@@ -106,6 +106,10 @@ pit_clkevt_mode(enum clock_event_mode mode, struct clock_event_device *dev)
 
 static void at91sam926x_pit_suspend(struct clock_event_device *cedev)
 {
+	/* Don't suspend PIT if unused */
+	if (cedev->mode == CLOCK_EVT_MODE_UNUSED)
+		return;
+
 	/* Disable timer */
 	pit_write(AT91_PIT_MR, 0);
 }
@@ -125,6 +129,10 @@ static void at91sam926x_pit_reset(void)
 
 static void at91sam926x_pit_resume(struct clock_event_device *cedev)
 {
+	/* Don't resume PIT if unused */
+	if (cedev->mode == CLOCK_EVT_MODE_UNUSED)
+		return;
+
 	at91sam926x_pit_reset();
 }
 
-- 
2.1.3

[PATCH] ARM: at91/pit: don't suspend/resume if unused

[Nicolas Ferre]

Le 17/12/2014 20:53, Sylvain Rochet a ?crit :
> 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@finsecur.com>

Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>

I also moved these changes to the new clocksource PIT driver. Cf. the
patch I've just sent titled: (clocksource: timer-atmel-pit: don't
suspend/resume if unused) (preserving your authorship of course).

Thanks. Bye.


> ---
>  arch/arm/mach-at91/at91sam926x_time.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/arm/mach-at91/at91sam926x_time.c b/arch/arm/mach-at91/at91sam926x_time.c
> index e3344b4..44526aa 100644
> --- a/arch/arm/mach-at91/at91sam926x_time.c
> +++ b/arch/arm/mach-at91/at91sam926x_time.c
> @@ -106,6 +106,10 @@ pit_clkevt_mode(enum clock_event_mode mode, struct clock_event_device *dev)
>  
>  static void at91sam926x_pit_suspend(struct clock_event_device *cedev)
>  {
> +	/* Don't suspend PIT if unused */
> +	if (cedev->mode == CLOCK_EVT_MODE_UNUSED)
> +		return;
> +
>  	/* Disable timer */
>  	pit_write(AT91_PIT_MR, 0);
>  }
> @@ -125,6 +129,10 @@ static void at91sam926x_pit_reset(void)
>  
>  static void at91sam926x_pit_resume(struct clock_event_device *cedev)
>  {
> +	/* Don't resume PIT if unused */
> +	if (cedev->mode == CLOCK_EVT_MODE_UNUSED)
> +		return;
> +
>  	at91sam926x_pit_reset();
>  }
>  
> 


-- 
Nicolas Ferre