Re: [PATCH 0/3] drm/radeon kexec fixes

[ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman)]

Alex Deucher <alexdeucher-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:

> On Mon, Sep 9, 2013 at 5:21 AM, Markus Trippelsdorf
> <markus-xp2qqqlHh3xzoYq+O6RWwA@public.gmane.org> 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