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

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Date:   Wed, 14 Dec 2022 09:38:28 +0100
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     phone-devel@...r.kernel.org, Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        ~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>,
        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 2022-12-14 01:02:14, Konrad Dybcio wrote:
> 
> 
> On 14.12.2022 00:22, 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")

Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>

> > ---
> Missing s-o-b

Thanks for catching, checkpatch would've pointed this out (in addition
to a typo in the cover letter) if I had ran it.

> >  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;