linux-kernel - Re: [PATCH RFC] drm/msm/dpu: Fall back to a single DSC encoder (1:1:1) on small SoCs

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Message-ID: <6g3dfqm274ykypbyz4sckyisg2t67ch7mvh2h6lbkt2lv5unaf@5jcffdimidmw>
Date: Wed, 22 Jan 2025 17:54:56 +0100
From: Marijn Suijten <marijn.suijten@...ainline.org>
To: Luca Weiss <luca.weiss@...rphone.com>
Cc: Rob Clark <robdclark@...il.com>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>, Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 
	Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, ~postmarketos/upstreaming@...ts.sr.ht, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Konrad Dybcio <konrad.dybcio@....qualcomm.com>, 
	Martin Botka <martin.botka@...ainline.org>, Jami Kettunen <jami.kettunen@...ainline.org>, 
	linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] drm/msm/dpu: Fall back to a single DSC encoder
 (1:1:1) on small SoCs

On 2025-01-21 16:58:24, Luca Weiss wrote:
> Hi Marijn,
> 
> On Tue Jan 21, 2025 at 12:06 AM CET, Marijn Suijten wrote:
> > Some SoCs such as SC7280 (used in the FairPhone 5) have only a single
> > DSC "hard slice" encoder.  The current hardcoded use of 2:2:1 topology
> > (2 LM and 2 DSC for a single interface) make it impossible to use
> > Display Stream Compression panels with mainline, which is exactly what's
> > installed on the FairPhone 5.
> 
> Nitpick, if you send another revision: s/FairPhone/Fairphone/
> 
> >
> > By loosening the hardcoded `num_dsc = 2` to fall back to `num_dsc =
> > 1` when the catalog only contains one entry, we can trivially support
> > this phone and unblock further panel enablement on mainline.  A few
> > more supporting changes in this patch ensure hardcoded constants of 2
> > DSC encoders are replaced to count or read back the actual number of
> > DSC hardware blocks that are enabled for the given virtual encoder.
> > Likewise DSC_MODE_SPLIT_PANEL can no longer be unconditionally enabled.
> 
> This unblocks panel enablement on upstream without any hacks on top.
> Many thanks!
> 
> Tested-by: Luca Weiss <luca.weiss@...rphone.com>

Thanks!  I fixed the Fairphone capitalization typo but forgot to roll up
your t-b (something about this being a long time ago and forgetting to run b4
trailers -u), but then the patch changed a little bit.

- Marijn