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From: ebiederm@xmission.com (Eric W. Biederman)
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Date: Tue, 10 Sep 2013 11:27:59 -0700
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 (Alex Deucher's message of "Mon, 9 Sep 2013 09:04:01 -0400")
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Subject: Re: [PATCH 0/3] drm/radeon kexec fixes
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To: Alex Deucher <alexdeucher@gmail.com>
Cc: Christian =?utf-8?Q?K=C3=B6nig?= <deathsimple@vodafone.de>, kexec@lists.infradead.org, Maling list - DRI developers <dri-devel@lists.freedesktop.org>, Markus Trippelsdorf <markus@trippelsdorf.de>

Alex Deucher <alexdeucher@gmail.com> writes:

> On Mon, Sep 9, 2013 at 5:21 AM, Markus Trippelsdorf
> <markus@trippelsdorf.de> wrote:
>
>> IIRC Alex said the sanity checks are expensive and boot-time could be
>> improved by dropping them. Maybe he can chime in?
>
> They shouldn't be necessary with a proper shutdown, but in this
> particular case, they are not very expensive.  What is expensive is
> having a separate sanity check functions for all the various hw blocks
> to teardown everything on startup prior to starting it up in case
> kexec, etc. left the system in a bad state.  It ends up amounting to a
> full tear down sequence followed by a full start up sequence every
> time you load the driver.
>
> I can't really comment on the first patch, but the rest seem fine.

Let me reask the question just a little bit.

Is it the sanity checks that are expensive?  Or is it the
reinitialization that is triggered by the sanity checks that is
expensive?

>From what Christian said in the other reply it sounds like this is a
game we will never completely win, but it would be nice to have half a
chance in the kexec on panic case to have video.  So I am curious to
know if the checks are expensive when we are coming at hardware in a
clean state.

Eric


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