[Intel-gfx] [PATCH 2/2] [v2] drm/i915: Disable GGTT PTEs on GEN6+ suspend

[Takashi Iwai]

At Wed, 16 Oct 2013 18:27:33 +0100,
Chris Wilson wrote:
> 
> On Wed, Oct 16, 2013 at 10:06:27AM -0700, Ben Widawsky wrote:
> > On Wed, Oct 16, 2013 at 05:58:31PM +0100, Chris Wilson wrote:
> > > So clearing the valid bit should result in the GPU reporting errors for
> > > delayed accesses, but none were reported?
> > 
> > So I can't actually reproduce the problem for some reason. Paulo will
> > need to answer. One theory is the fault information is lost on suspend.
> > 
> > The original patch put faults both in suspend, and resume. After this, I
> > asked Paulo to wedge the GPU, and there I saw faults.
> 
> If we can capture the error, and it should be very possible to do so, we
> should be able to pinpoint the cause quite quickly. If it is just deferred
> writes, it should also be a problem across module unload - which should
> be easier for getting debug information out.

The bug is only about S4, thus it's not so easy to capture anything in
the resume kernel, as all lost after transition to the restored
kernel.

BTW, I also suspect that the similar problem might still happen in
other cases, e.g. via kexec even with this patch.


thanks,

Takashi