[Intel-gfx] [PATCH] drm/i915: Disable outputs during unregister

[Ville Syrjälä]

On Tue, Dec 01, 2020 at 10:38:57PM +0000, Chris Wilson wrote:
> Quoting Ville Syrjälä (2020-12-01 16:05:17)
> > On Fri, Nov 27, 2020 at 10:05:48PM +0000, Chris Wilson wrote:
> > > Switch off the scanout during driver unregister, so we can shutdown the
> > > HW immediately for unbind.
> > > 
> > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > > ---
> > >  drivers/gpu/drm/i915/i915_drv.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > > index 320856b665a1..62d188e5cb8d 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.c
> > > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > > @@ -738,6 +738,7 @@ static void i915_driver_unregister(struct drm_i915_private *dev_priv)
> > >        * events.
> > >        */
> > >       drm_kms_helper_poll_fini(&dev_priv->drm);
> > > +     drm_atomic_helper_shutdown(&dev_priv->drm);
> > 
> > Looks like we already have this in remove(). Is that too late?
> 
> For the operations we do during unbind, yes.
> 
> For the core_hotplug/rebind dance, we have to reset the GPU while we
> still have runtime-pm operational and have pushed the reset to
> unregister (from experimentation that's as late as we can put it where
> the GPU works after rebinding and we don't corrupt the system on unbind,
> with the current hooks). You can guess how well gen3 likes that.
> 
> But I don't think the right answer is to skip the reset for gen3.
> Suppose we enable context support for gen3, then the reset would be
> required as well, and so we would still need the whole display
> shenanigans to turn it off. Moving the modeset to turn the display off
> to the end of userspace seems reasonable.

Yeah, just a bit odd to have the same call twice in the
sequence. Can we remove the second call at least?

Also a bit annoying the unload sequence no longer matches the
suspend sequence. Well, I guess it was never 100% anyway but
I think it was a bit closer before this patch. But the whole
thing is rather messy anyway so I guess t's not significantly
worse after this.

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

-- 
Ville Syrjälä
Intel