Subject: Re: [PATCH] powerpc/powernv/idle: Round up latency and residency values

From: Michael Ellerman <[email-masked]>
Date: Thu, 24 Aug 2017 20:28:19 +1000

Vaidyanathan Srinivasan <[email-masked]> writes:

> On PowerNV platforms, firmware provides exit latency and
> target residency for each of the idle states in nano
> seconds.  Cpuidle framework expects the values in micro
> seconds.  Round up to nearest micro seconds to avoid errors
> in cases where the values are defined as fractional micro
> seconds.
>
> Default idle state of 'snooze' has exit latency of zero.  If
> other states have fractional micro second exit latency, they
> would get rounded down to zero micro second and make cpuidle
> framework choose deeper idle state when snooze loop is the
> right choice.
>
> Reported-by: Anton Blanchard <[email-masked]>
> Signed-off-by: Vaidyanathan Srinivasan <[email-masked]>

This sounds like a fairly bad bug, does it need a Fixes / Cc stable tag?

cheers