linux-kernel - RE: Regression in intel_idle on Avaton/Rangely Mohon Peak board

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Date:	Wed, 2 Apr 2014 21:58:42 +0000
From:	"Brown, Len" <len.brown@...el.com>
To:	"Gortmaker, Paul (Wind River)" <paul.gortmaker@...driver.com>
CC:	"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
	Arne Bockholdt <linux-kernel@...kholdt.com>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: Regression in intel_idle on Avaton/Rangely Mohon Peak board

> [    0.840668] intel_idle: lapic_timer_reliable_states 0x2
vs.
> [    0.877528] intel_idle: lapic_timer_reliable_states 0xffffffff

This means CPUID.ARAT is set for the new board, and not set
for the old board.  You can observe that also in /proc/cpuinfo flags
where you will likely also find a visible stepping difference between
these two boards.

Bring-up Avoton had ARAT disabled, and also had broken deep C-states.
It looks like that is what your old board has.  Throw it away and
use only production steppings.  If you are stuck w/ pre-production hardware,
then you need to manually modify upstream Linux to make it happy --
since upstream Linux only cares about production hardware.

thanks,
-Len

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