linux-kernel - Re: [PATCH 1/3] powernow-k6: disable cache when changing frequency

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Message-ID: <CAKohpo=_0i43EDSoOAm2ROwEmu9__p+MyoObcLPoZWxUB5XmDA@mail.gmail.com>
Date:	Tue, 17 Dec 2013 14:15:01 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Mikulas Patocka <mpatocka@...hat.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] powernow-k6: disable cache when changing frequency

On 12 December 2013 06:08, Mikulas Patocka <mpatocka@...hat.com> wrote:
> During frequency transition the processor is in "EPM Stop Grant" state.
> The documentation says that the processor doesn't respond to inquiry
> requests in this state. Consequently, coherency of processor caches and
> bus master devices is not maintained, causing the system instability.
>
> This patch flushes the cache during frequency transition. It fixes the
> instability.

I don't have much idea of these systems but wouldn't this affect performance
badly?
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