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

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: "Navare, Manasi" <manasi.d.navare@intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	Daniel Stone <daniels@collabora.com>
Subject: Re: [PATCH] drm/atomic: Add the crtc to affected crtc only if uapi.enable = true
Date: Fri, 19 Mar 2021 23:27:59 +0200	[thread overview]
Message-ID: <YFUXX/pDcBheiNWL@intel.com> (raw)
In-Reply-To: <20210319212624.GA6560@labuser-Z97X-UD5H>

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.

-- 
Ville Syrjälä
Intel
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