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

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Date:   Mon, 22 May 2023 14:45:01 -0700
From:   Jessica Zhang <quic_jesszhan@...cinc.com>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
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 5/22/2023 1:44 PM, Marijn Suijten wrote:
> 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.

Hi Marijn,

I don't see any explicit documentation on the order of R-b tags. FWIW, I 
see in the git log that S-o-b always goes at the bottom of the commit 
message.

I would prefer the S-o-b to always be at the bottom (as it helps me 
avoid duplicate S-o-b's when doing `git commit -s`), though I can flip 
the order of the R-b and suggested-by tags.

Thanks,

Jessica Zhang

> 
> - 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
>>