Re: [PATCH v2] clocksource: arm_global_timer: fix suspend resume

From: santosh shilimkar
Date: Fri Nov 20 2015 - 13:53:18 EST

On 11/20/2015 10:46 AM, Marc Zyngier wrote:
On 20/11/15 18:35, Grygorii Strashko wrote:
Hi Santosh,

On 11/20/2015 07:23 PM, santosh shilimkar wrote:
+ Thomas, Marc

On 11/20/2015 5:57 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 - SysRq are working, but
nothing else. The reason of stall is that ARM Global timer loses its

The reason of stall is that ARM Global timer loses its contexts during
System suspend:

Hence, update ARM Global timer driver to reflect above behaviour
- re-enable ARM Global timer on resume GT_CONTROL.TIMER_ENABLE = 1
- ensure clocksource and clockevent devices have coresponding flags
depending on presence of "always-on" DT property.

Something which loses context in low power states can't be
called "always-on"

Sry, it's kinda new area for me and I could make mistakes.

While working on this patch I've:
- re-used implementation from ARM arch timer
commit 82a5619410d4c4df65c04272db198eca5a867c18
Author: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Date: Tue Apr 8 10:04:32 2014 +0100

clocksource: arch_arm_timer: Fix age-old arch timer C3STOP detection issue


This patch has a very specific purpose: instructing the core code that
this timer will never stop ticking, ever. It is really targeted at
virtual machines, whose timer is backed by the host timer, even when the
VM is not running.

Using it on actual hardware is may not be the best idea, specially in
the presence of PM.

Exactly. Thanks for clarifying the commit Marc.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at