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

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Message-ID: <565C3852.4000605@ti.com>
Date:	Mon, 30 Nov 2015 13:51:46 +0200
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	"santosh.shilimkar@...cle.com" <santosh.shilimkar@...cle.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 11/30/2015 02:29 AM, santosh.shilimkar@...cle.com wrote:
> 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>

Sure, I'll update.

Thanks.
-- 
regards,
-grygorii
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