[PATCH 1/2] ARM: EXYNOS: Support Suspend-to-RAM on EXYNOS5420

[Tomasz Figa]

Hi,

On Friday 20 of December 2013 15:56:38 sunil joshi wrote:
> Hi Abhilash,
> I saw another patch in chrome tree ..by Andrew Bresticker
> which may be relevant here ..
> 
> Just wondering if you missed adding this ? or this is not needed ?
> You did not face any issue in getting core to suspend ?
> 
> ------------------------------------------------------------------------------------------
> commit 95402d816b9f1a05ce633f7ff64b4c939c142482
> Author: Andrew Bresticker <abrestic at chromium.org>
> Date:   Mon Jul 15 13:14:36 2013 -0700
> 
>     arm: exynos: disable all interrupts on Exynos5420 before suspend
> 
>     Disable all interrupts from the GIC before entering suspend on
>     Exynos5420 as is done on Exynos5250.  If interrupts are enabled, we
>     may receive an interrupt after entering WFI but before the PMU has
>     suspended the system, causing suspend to fail.
> 
>     BUG=chrome-os-partner:20523
>     TEST=Run suspend_stress_test on Pit and observe that entering suspend
>     no longer occasionally fails with the "Failed to suspend the system"
>     error in exynos_cpu_suspend().

A question about this for Chromium and LSI guys:

If you find out that there is already a pending interrupt before you enter
the sleep mode, isn't it more reasonable to cancel the process ASAP and
handle the event instead of entering the sleep just to leave it?

I believe this should be both more efficient with respect to power usage
and latency, because sleep-wakeup transition takes time and power.

Do you have any reason to think the opposite?

Best regards,
Tomasz