[Intel-gfx] [PATCH 1/2] drm/i915/gt: Allow clobbering gpu resets if the display is off

[Chris Wilson]

Quoting Ville Syrjälä (2019-09-10 08:39:31)
> On Mon, Sep 09, 2019 at 11:55:35PM +0100, Chris Wilson wrote:
> > If the display is inactive, we need not worry about the gpu reset
> > clobbering the display!
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/gt/intel_reset.c | 18 +++++++++++++++++-
> >  1 file changed, 17 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
> > index b9d84d52e986..fe57296b790c 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_reset.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_reset.c
> > @@ -7,6 +7,7 @@
> >  #include <linux/sched/mm.h>
> >  #include <linux/stop_machine.h>
> >  
> > +#include "display/intel_display.h"
> >  #include "display/intel_display_types.h"
> >  #include "display/intel_overlay.h"
> >  
> > @@ -729,6 +730,21 @@ static void nop_submit_request(struct i915_request *request)
> >       intel_engine_queue_breadcrumbs(engine);
> >  }
> >  
> > +static bool reset_clobbers_display(struct drm_i915_private *i915)
> > +{
> > +     struct intel_crtc *crtc;
> > +
> > +     if (!INTEL_INFO(i915)->gpu_reset_clobbers_display)
> > +             return false;
> > +
> > +     for_each_intel_crtc(&i915->drm, crtc) {
> > +             if (crtc->active)
> > +                     return true;
> > +     }
> 
> This feels racy. crtc->active gets set somewhere in the middle of the
> modeset, so looks like now we could clobber all the stuff we've already
> set up before crtc->active got set.

The question is, does it matter? After we unwedge, we clobber again for
realz. Not that we have anything deliberately trying to race
wedge-vs-modeset(on/off).
-Chris