Re: [Intel-gfx] [PATCH] drm/atomic: Add the crtc to affected crtc only if uapi.enable = true

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Apr 01, 2021 at 02:49:13PM -0700, Navare, Manasi wrote:
> On Fri, Mar 26, 2021 at 06:15:22PM +0200, Ville Syrjälä wrote:
> > On Thu, Mar 25, 2021 at 03:01:29PM -0700, Navare, Manasi wrote:
> > > On Fri, Mar 19, 2021 at 11:27:59PM +0200, Ville Syrjälä wrote:
> > > > On Fri, Mar 19, 2021 at 02:26:24PM -0700, Navare, Manasi wrote:
> > > > > On Fri, Mar 19, 2021 at 11:12:41PM +0200, Ville Syrjälä wrote:
> > > > > > On Fri, Mar 19, 2021 at 01:54:13PM -0700, Navare, Manasi wrote:
> > > > > > > On Fri, Mar 19, 2021 at 04:56:24PM +0200, Ville Syrjälä wrote:
> > > > > > > > On Thu, Mar 18, 2021 at 04:01:26PM -0700, Navare, Manasi wrote:
> > > > > > > > > So basically we see this warning only in case of bigjoiner when
> > > > > > > > > drm_atomic_check gets called without setting the state->allow_modeset flag.
> > > > > > > > 
> > > > > > > > Considering the code is 'WARN(!state->allow_modeset, ...' that
> > > > > > > > fact should be rather obvious.
> > > > > > > > 
> > > > > > > > > 
> > > > > > > > > So do you think that in i915, in intel_atomic_check_bigjoiner() we should only
> > > > > > > > > steal the crtc when allow_modeset flag is set in state?
> > > > > > > > 
> > > > > > > > No. If you fully read drm_atomic_check_only() you will observe
> > > > > > > > that it will reject any commit w/ allow_modeset==false which 
> > > > > > > > needs a modeset. And it does that before the WARN.
> > > > > > > > 
> > > > > > > > So you're barking up the wrong tree here. The problem I think
> > > > > > > > is that you're just computing requested_crtcs wrong.
> > > > > > > 
> > > > > > > So here in this case, requested CRTC = 0x1 since it requests modeset on CRTC 0
> > > > > > > Now in teh atomic check, it steals the slave CRTC 1 and hence affected CRTC comes out
> > > > > > > as 0x3 and hence the mismatch.
> > > > > > 
> > > > > > Hmm. How can it be 0x3 if we filtered out the uapi.enable==false case?
> > > > > > 
> > > > > 
> > > > > Yes if I add that condition like in this patch then it correctly calculates
> > > > > the affected crtc bitmask as only 0x1 since it doesnt include the slave crtc.
> > > > > So with this patch, requested crtc = 0x 1, affected crtc = 0x1
> > > > > 
> > > > > If this looks good then this fixes our bigjoiner warnings.
> > > > > Does this patch look good to you as is then?
> > > > 
> > > > I think you still need to fix the requested_crtcs calculation.
> > > 
> > > We calculate requested crtc at the beginning :
> > > for_each_new_crtc_in_state(state, crtc, new_crtc_state, i)
> > >                 requested_crtc |= drm_crtc_mask(crtc);
> > > 
> > > Are you suggesting adding this to after:
> > >  if (config->funcs->atomic_check) {
> > >                 ret = config->funcs->atomic_check(state->dev, state);
> > > 
> > >                 if (ret) {
> > >                         DRM_DEBUG_ATOMIC("atomic driver check for %p failed: %d\n",
> > >                                          state, ret);
> > >                         return ret;
> > >                 }
> > > 		requested_crtc |= drm_crtc_mask(crtc);    // Here it will have requested crtc = 0x11
> > >         }
> > > 
> > > in this case here the state should already have master crtc 0 and slave crtc 1
> > > and that requested crtc should already be 0x11
> > > 
> > > Then in that case we dont need any special check for calculating affected crtc, that also will be 0x11
> > 
> > All I'm saying is that you're currently calculating requested_crtcs and
> > affected_crtcs differently. So I'm not at all surprised that they might
> > not match.
> >
> 
> I dont get your point yet.
> requested crtc is calculated before the atomic check call and we dont check for crtc uapi.enable to be true.
> And hence requested crtc  = CRTC 0 = 0x2
> After I added the check in this patch where affected crtc will include only the crtcs that have uapi.enable = true
> then  it perfectly matches the requested crtc and return 0x2 but without this check when the calculation of
> requested and affected crtc is the same is where we see the affected crtc = CRTC 0 and 1 = 0x3
> 
> So when the calculation is different infcat we dont see the mismatch
> 
> What is your point here?

Try doing an atomic commit wiht both crtcs already added in by 
userspace. I think that will still WARN.

-- 
Ville Syrjälä
Intel