linux-kernel - Re: [PATCH] drm/msm/dpu: correct LM pairing for SM6150

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Message-ID: <55dalo6ecncyceb6wmu7nm6hco4vixxox5grelykkdw5q6yjys@tac57c5nowsd>
Date: Tue, 17 Dec 2024 00:23:30 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Li Liu <quic_lliu6@...cinc.com>, 
	Fange Zhang <quic_fangez@...cinc.com>, linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/dpu: correct LM pairing for SM6150

On Mon, Dec 16, 2024 at 11:26:37AM -0800, Abhinav Kumar wrote:
> 
> 
> On 12/16/2024 12:20 AM, Dmitry Baryshkov wrote:
> > According to the vendor devicetree on SM6150 LM_0 is paired with LM_2
> > rather than LM_1. Correct pairing indices.
> > 
> > Fixes: cb2f9144693b ("drm/msm/dpu: Add SM6150 support")
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > ---
> >   drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_5_3_sm6150.h | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_5_3_sm6150.h b/drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_5_3_sm6150.h
> > index 621a2140f675fa28b3a7fcd8573e59b306cd6832..81eb274cc7000a3b70b0f6650088ddcd24648eab 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_5_3_sm6150.h
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_5_3_sm6150.h
> > @@ -116,20 +116,20 @@ static const struct dpu_lm_cfg sm6150_lm[] = {
> >   		.sblk = &sdm845_lm_sblk,
> >   		.pingpong = PINGPONG_0,
> >   		.dspp = DSPP_0,
> > -		.lm_pair = LM_1,
> > +		.lm_pair = LM_2,
> >   	}, {
> >   		.name = "lm_1", .id = LM_1,
> >   		.base = 0x45000, .len = 0x320,
> >   		.features = MIXER_QCM2290_MASK,
> >   		.sblk = &sdm845_lm_sblk,
> >   		.pingpong = PINGPONG_1,
> > -		.lm_pair = LM_0,
> >   	}, {
> >   		.name = "lm_2", .id = LM_2,
> >   		.base = 0x46000, .len = 0x320,
> >   		.features = MIXER_QCM2290_MASK,
> >   		.sblk = &sdm845_lm_sblk,
> >   		.pingpong = PINGPONG_2,
> > +		.lm_pair = LM_0,
> >   	},
> >   };
> 
> Have a basic question here. We check the peer only if we will have more than
> one LM needed in the topology but sm6150 does not have 3dmux, so the number
> of LMs will not go beyond one.
> 
> 318 		/* Valid primary mixer found, find matching peers */
> 319 		if (lm_count < reqs->topology.num_lm) {
> 
> It seems like this fix will be unused or does not really matter.
> 
> Downstream has a different implementation for lm_pair, its used even to
> decide the LM pair for CWB mux. Upstream has a simpler implementation of
> just doing that in the code of using ODD LMs for ODD CWB muxes and even LMs
> for even CWB muxes. So fix is okay but not needed.

So which topology is supposed to work with LM_0 / LM_2 pair?

I'd still prefer to land the fix for the sake of catalog having the
correct data.

> 
> > 
> > ---
> > base-commit: a3d570eace66b4016f2692a6f1045742ee70c6b1
> > change-id: 20241216-dpu-fix-sm6150-17f0739f8fe0
> > 
> > Best regards,

-- 
With best wishes
Dmitry