Re: [PATCH] drm/i915: provide more error output when mode sets fail

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Wed, 20 Jul 2011 01:14:47 +0100
Chris Wilson <chris@chris-wilson.co.uk> wrote:

> On Tue, 19 Jul 2011 15:38:56 -0700, Jesse Barnes
> <jbarnes@virtuousgeek.org> wrote:
> > If a mode set fails we may get a message from drm_crtc_helper if
> > we're lucky, but it won't tell us anything about *why* we failed to
> > set a mode.  So add a few DRM_ERRORs for the cases that shouldn't
> > happen so we can debug things more easily.
> 
> Also fix drm not to simply ignore the error codes would also be
> useful. But how does logging the error without logging the state
> help? Presumably you are targeting the unreproducible cases?

I added these to catch a mode setting failure Keith was seeing
following a GPU hang.  The simple debug info was enough to track things
down.  But I agree, really the DRM hooks should return ints and give us
more info about what happened, and try to roll back the config.

> >  	if (!crtc->fb) {
> > -		DRM_DEBUG_KMS("No FB bound\n");
> > +		DRM_ERROR("No FB bound\n");
> >  		return 0;
> >  	}
> 
> Should this be flagged as en error then?

Possibly, unless we shut off displays this way??

> > @@ -1952,6 +1953,7 @@ intel_pipe_set_base(struct drm_crtc *crtc,
> > int x, int y, NULL);
> >  	if (ret != 0) {
> >  		mutex_unlock(&dev->struct_mutex);
> > +		DRM_ERROR("pin & fence failed\n");
> 
> In this and the following, report the reason/error code for the
> failure. -Chris

Sure.

Jesse