[Intel-gfx] [PATCH] drm/i915: Stop gathering error states for CS error interrupts

[Daniel Vetter]

On Wed, Nov 05, 2014 at 08:35:01AM +0000, Chris Wilson wrote:
> On Tue, Nov 04, 2014 at 03:52:22PM +0100, Daniel Vetter wrote:
> > There's quite a few bug reports with error states where the error
> > reasons makes just about no sense at all. Like dying on tlbs for a
> > display plane that's not even there. Also users don't really report a
> > lot of bad side effects generally, just the error states.
> > 
> > Furthermore we don't even enable these interrupts any more on gen5+
> > (though the handling code is still there). So this mostly concerns old
> > platforms.
> > 
> > Given all that lets make our lives a bit easier and stop capturing
> > error states, in the hopes that we can just ignore them. In case
> > that's not true and the gpu indeed dies the hangcheck should
> > eventually kick in. And I've left some debug log in to make this case
> > noticeble. Referenced bug is just an example.
> 
> The problem is they can be useful. They have shown when our modesetting
> sequence has been completely snafu, and they can also be used to detect
> page faults (but that does require a bit of kernel trickery) in
> userspace GPU command streams. Even in the Display B on 845g, we must
> have done something to upset the hardware, but we simply haven't
> captured what. I am not yet convinced we want to throw all such reports
> away, in case we do ignore genuine fail.
> 
> How about just toning down the error message for non-fatal faults, and
> discarding the earlier error state should we get a fatal fault afterwards?

Hm yeah, that might work too.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch