linux-kernel - Re: [PATCH v3] clocksource: arm_global

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Date:	Sun, 29 Nov 2015 16:29:29 -0800
From:	"santosh.shilimkar@...cle.com" <santosh.shilimkar@...cle.com>
To:	Grygorii Strashko <grygorii.strashko@...com>,
	Russell King <linux@....linux.org.uk>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Srinivas Kandagatla <srinivas.kandagatla@...il.com>,
	Maxime Coquelin <maxime.coquelin@...com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kernel@...inux.com, linux-omap@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>,
	John Stultz <john.stultz@...aro.org>,
	Felipe Balbi <balbi@...com>, Tony Lindgren <tony@...mide.com>,
	Santosh Shilimkar <ssantosh@...nel.org>,
	Marc Zyngier <marc.zyngier@....com>
Subject: Re: [PATCH v3] clocksource: arm_global_timer: fix suspend resume

On 11/27/15 11:47 AM, Grygorii Strashko wrote:
> Now the System stall is observed on TI AM437x based board
> (am437x-gp-evm) during resuming from System suspend when ARM Global
> timer is selected as clocksource device (CPUIdle not enabled) - SysRq are working,
> but nothing else.
>
> The reason of stall is that ARM Global timer loses its contexts during
> System suspend:
>     GT_CONTROL.TIMER_ENABLE = 0 (unbanked)
>     GT_COUNTERx = 0
>
> Hence, update ARM Global timer driver to reflect above behaviour
> - re-enable ARM Global timer on resume GT_CONTROL.TIMER_ENABLE = 1.
>
> CC: Arnd Bergmann <arnd@...db.de>
> Cc: John Stultz <john.stultz@...aro.org>
> Cc: Felipe Balbi <balbi@...com>
> Cc: Tony Lindgren <tony@...mide.com>
> Cc: Santosh Shilimkar <ssantosh@...nel.org>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
> ---
> Changes in v3:
>   - dropped all DT specific code
> Changes in v2:
>   - suspend/resume simplified: nothing is stored any more and
>     ARM GT just re-enabled
> Link on v2:
>   https://lkml.org/lkml/2015/11/20/355
> Link on v1:
>   https://lkml.org/lkml/2015/11/13/456
>
Looks reasonable to me.
>   drivers/clocksource/arm_global_timer.c | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/drivers/clocksource/arm_global_timer.c b/drivers/clocksource/arm_global_timer.c
> index a2cb6fa..10d1417 100644
> --- a/drivers/clocksource/arm_global_timer.c
> +++ b/drivers/clocksource/arm_global_timer.c
> @@ -195,12 +195,19 @@ static cycle_t gt_clocksource_read(struct clocksource *cs)
>   	return gt_counter_read();
>   }
>
> +static void gt_resume(struct clocksource *cs)
> +{
> +	/* re-enable timer on resume */
> +	writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);

Check if its disabled before enabling it.
Other than that,
Reviewed-by: Santosh Shilimkar <ssantosh@...nel.org>
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