Re: [PATCH v3] clocksource: arm_global_timer: fix suspend resume

From: santosh.shilimkar@xxxxxxxxxx
Date: Sun Nov 29 2015 - 19:31:10 EST


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@xxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Felipe Balbi <balbi@xxxxxx>
Cc: Tony Lindgren <tony@xxxxxxxxxxx>
Cc: Santosh Shilimkar <ssantosh@xxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
---
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@xxxxxxxxxx>
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