linux-kernel - Re: [PATCH v2 2/2] drm/msm/disp: Correct porch timing for SDM845

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Message-ID: <5yli2sqw5hxoinlaguxjq2lleez7p4qjkwvexrgn7uphnu44ws@trlvdrpep5uv>
Date: Thu, 13 Feb 2025 02:04:23 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: "James A. MacInnes" <james.a.macinnes@...il.com>
Cc: Rob Clark <robdclark@...il.com>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Chandan Uddaraju <chandanu@...eaurora.org>, 
	Stephen Boyd <swboyd@...omium.org>, Vara Reddy <quic_varar@...cinc.com>, 
	Tanmay Shah <tanmay@...eaurora.org>, linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	Guenter Roeck <groeck@...omium.org>, Rob Clark <robdclark@...omium.org>
Subject: Re: [PATCH v2 2/2] drm/msm/disp: Correct porch timing for SDM845

On Wed, Feb 12, 2025 at 03:03:47PM -0800, James A. MacInnes wrote:
> Type-C DisplayPort inoperable due to incorrect porch settings.
> - Re-used wide_bus_en as flag to prevent porch shifting

Unfortunately I don't know enough details to comment on this change.
Maybe Abhinav can check it. I can only notice that msm-4.14 disables
programmable_fetch_config for non-DSI calls. Would disabling that call
for DP interface fix your issue?

> 
> Fixes: c943b4948b58 ("drm/msm/dp: add displayPort driver support")
> Signed-off-by: James A. MacInnes <james.a.macinnes@...il.com>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
> index abd6600046cb..a21addc4794f 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
> @@ -94,17 +94,21 @@ static void drm_mode_to_intf_timing_params(
>  		timing->vsync_polarity = 0;
>  	}
>  
> -	/* for DP/EDP, Shift timings to align it to bottom right */
> -	if (phys_enc->hw_intf->cap->type == INTF_DP) {
> +	timing->wide_bus_en = dpu_encoder_is_widebus_enabled(phys_enc->parent);
> +	timing->compression_en = dpu_encoder_is_dsc_enabled(phys_enc->parent);
> +
> +	/*
> +	 *  For DP/EDP, Shift timings to align it to bottom right.
> +	 *  wide_bus_en is set for everything excluding SDM845 &
> +	 *  porch changes cause DisplayPort failure and HDMI tearing.
> +	 */
> +	if (phys_enc->hw_intf->cap->type == INTF_DP && timing->wide_bus_en) {
>  		timing->h_back_porch += timing->h_front_porch;
>  		timing->h_front_porch = 0;
>  		timing->v_back_porch += timing->v_front_porch;
>  		timing->v_front_porch = 0;
>  	}
>  
> -	timing->wide_bus_en = dpu_encoder_is_widebus_enabled(phys_enc->parent);
> -	timing->compression_en = dpu_encoder_is_dsc_enabled(phys_enc->parent);
> -
>  	/*
>  	 * for DP, divide the horizonal parameters by 2 when
>  	 * widebus is enabled
> 
> -- 
> 2.43.0
> 

-- 
With best wishes
Dmitry