Re: [PATCH] drm/i915: optionally check GTT checksum across suspend/resume

[Ben Widawsky <ben@bwidawsk.net>]

On Wed, 12 Sep 2012 13:27:10 -0700
Jesse Barnes <jbarnes@virtuousgeek.org> wrote:

> This adds a module parameter, gtt_suspend_verify, that will enable a
> simple GTT checksum across suspend and resume.
> 
> We currently spend a good amount of time (>20ms) clearing all the GTT
> PTEs at resume time, even though this may not be necessary on some
> machines.  This debug feature is intended to help determine whether
> newer machines don't need the unconditional GTT clear on resume.
> 
> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>


It's a cool idea, but I'd vote against adding a module parameter to
verify it. Daniel's trees should be well enough tested that
you could just disable it on IVB+ or whatever and let it go through QA
and developer testing. Aside from that, a debugfs flag to toggle it
would probably be a little better.

Also, as a bikeshed you could probably get a much better detection with
a CRC or something similar.

I dunno, just a thought,
-- 
Ben Widawsky, Intel Open Source Technology Center