linux-kernel - Re: [RFC PATCH 5/6] drm/msm/dsi: Flip greater-than check for slice_count and slice_per

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Message-ID: <642b0063-b3b1-fb01-b761-dfd30cea1c8c@quicinc.com>
Date:   Fri, 16 Dec 2022 16:31:55 -0800
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Marijn Suijten <marijn.suijten@...ainline.org>,
        <phone-devel@...r.kernel.org>, Rob Clark <robdclark@...il.com>,
        "Dmitry Baryshkov" <dmitry.baryshkov@...aro.org>,
        Vinod Koul <vkoul@...nel.org>
CC:     <~postmarketos/upstreaming@...ts.sr.ht>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        "Stephen Boyd" <swboyd@...omium.org>,
        Bjorn Andersson <andersson@...nel.org>,
        "Jessica Zhang" <quic_jesszhan@...cinc.com>,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        "Jani Nikula" <jani.nikula@...el.com>,
        sunliming <sunliming@...inos.cn>,
        "Sam Ravnborg" <sam@...nborg.org>,
        Haowen Bai <baihaowen@...zu.com>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Loic Poulain <loic.poulain@...aro.org>,
        "Vinod Polimera" <quic_vpolimer@...cinc.com>,
        Douglas Anderson <dianders@...omium.org>,
        Vladimir Lypak <vladimir.lypak@...il.com>,
        <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 5/6] drm/msm/dsi: Flip greater-than check for
 slice_count and slice_per_intf



On 12/13/2022 3:22 PM, Marijn Suijten wrote:
> According to downstream /and the comment copied from it/ this comparison
> should be the other way around.  In other words, when the panel driver
> requests to use more slices per packet than what could be sent over this
> interface, it is bumped down to only use a single slice per packet (and
> strangely not the number of slices that could fit on the interface).
> 
> Fixes: 08802f515c3c ("drm/msm/dsi: Add support for DSC configuration")

Like others have said, with SOB,
Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
> ---
>   drivers/gpu/drm/msm/dsi/dsi_host.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index 0686c35a6fd4..9bdfa0864cdf 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -855,11 +855,11 @@ static void dsi_update_dsc_timing(struct msm_dsi_host *msm_host, bool is_cmd_mod
>   	 */
>   	slice_per_intf = DIV_ROUND_UP(hdisplay, dsc->slice_width);
>   
> -	/* If slice_per_pkt is greater than slice_per_intf
> +	/* If slice_count is greater than slice_per_intf
>   	 * then default to 1. This can happen during partial
>   	 * update.
>   	 */
> -	if (slice_per_intf > dsc->slice_count)
> +	if (dsc->slice_count > slice_per_intf)
>   		dsc->slice_count = 1;
>   
>   	total_bytes_per_intf = dsc->slice_chunk_size * slice_per_intf;