linux-kernel - Re: [PATCH v4 1/5] msm/drm/dsi: Round up DSC hdisplay calculation

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Date:   Mon, 22 May 2023 22:44:07 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Jessica Zhang <quic_jesszhan@...cinc.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>,
        Daniel Vetter <daniel@...ll.ch>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/5] msm/drm/dsi: Round up DSC hdisplay calculation

On 2023-05-22 13:30:20, Jessica Zhang wrote:
> Currently, when compression is enabled, hdisplay is reduced via integer
> division. This causes issues for modes where the original hdisplay is
> not a multiple of 3.
> 
> To fix this, use DIV_ROUND_UP to divide hdisplay.
> 
> Reviewed-by: Marijn Suijten <marijn.suijten@...ainline.org>
> Suggested-by: Marijn Suijten <marijn.suijten@...ainline.org>

Nit: probably these should go in the opposite order.  And if they're
all supposed to be chronological, I think it is:

    Suggested-by:
    Fixes:
    Signed-off-by:
    Reviewed-by:

But unsure if that's a hard requirement, or even correct at all.

- Marijn

> Fixes: 08802f515c3cf ("drm/msm/dsi: Add support for DSC configuration")
> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
> ---
>  drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index 9223d7ec5a73..18d38b90eb28 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -952,7 +952,7 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
>  		 * pulse width same
>  		 */
>  		h_total -= hdisplay;
> -		hdisplay = msm_dsc_get_bytes_per_line(msm_host->dsc) / 3;
> +		hdisplay = DIV_ROUND_UP(msm_dsc_get_bytes_per_line(msm_host->dsc), 3);
>  		h_total += hdisplay;
>  		ha_end = ha_start + hdisplay;
>  	}
> 
> -- 
> 2.40.1
>