[PATCH v3] clocksource: arm_global_timer: fix suspend resume

[PATCH v3] clocksource: arm_global_timer: fix suspend resume

[Grygorii Strashko]

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@arndb.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Santosh Shilimkar <ssantosh@kernel.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.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

 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);
+}
+
 static struct clocksource gt_clocksource = {
 	.name	= "arm_global_timer",
 	.rating	= 300,
 	.read	= gt_clocksource_read,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	.resume = gt_resume,
 };
 
 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
-- 
2.6.3

[PATCH v3] clocksource: arm_global_timer: fix suspend resume

[santosh.shilimkar at oracle.com]

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@arndb.de>
> Cc: John Stultz <john.stultz@linaro.org>
> Cc: Felipe Balbi <balbi@ti.com>
> Cc: Tony Lindgren <tony@atomide.com>
> Cc: Santosh Shilimkar <ssantosh@kernel.org>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.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@kernel.org>

[PATCH v3] clocksource: arm_global_timer: fix suspend resume

[Grygorii Strashko]

On 11/30/2015 02:29 AM, santosh.shilimkar at oracle.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@arndb.de>
>> Cc: John Stultz <john.stultz@linaro.org>
>> Cc: Felipe Balbi <balbi@ti.com>
>> Cc: Tony Lindgren <tony@atomide.com>
>> Cc: Santosh Shilimkar <ssantosh@kernel.org>
>> Cc: Marc Zyngier <marc.zyngier@arm.com>
>> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.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@kernel.org>

Sure, I'll update.

Thanks.
-- 
regards,
-grygorii