linux-kernel - Re: [PATCH v5 2/6] drm/msm/dpu: adjust data width for widen bus case

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Date: Tue, 28 May 2024 03:48:09 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Jun Nie <jun.nie@...aro.org>
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>, 
	Daniel Vetter <daniel@...ll.ch>, Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Vinod Koul <vkoul@...nel.org>, linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/6] drm/msm/dpu: adjust data width for widen bus case

On Mon, May 27, 2024 at 10:21:48PM +0800, Jun Nie wrote:
> data is valid for only half the active window if widebus
> is enabled
> 
> Signed-off-by: Jun Nie <jun.nie@...aro.org>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
> index 225c1c7768ff..f97221423249 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
> @@ -168,6 +168,15 @@ static void dpu_hw_intf_setup_timing_engine(struct dpu_hw_intf *intf,
>  
>  	data_width = p->width;
>  
> +	/*
> +	 * If widebus is enabled, data is valid for only half the active window
> +	 * since the data rate is doubled in this mode. But for the compression
> +	 * mode in DP case, the p->width is already adjusted in
> +	 * drm_mode_to_intf_timing_params()

Is there any reason for divergence here?

> +	 */
> +	if (p->wide_bus_en && !dp_intf)
> +		data_width = p->width >> 1;
> +
>  	hsync_data_start_x = hsync_start_x;
>  	hsync_data_end_x =  hsync_start_x + data_width - 1;
>  
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry