linux-kernel - Re: [PATCH 18/35] drm/msm/dpu: get rid of DPU_PINGPONG

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Message-ID: <c3c70f9a-7a1c-4575-af93-b519117d0084@quicinc.com>
Date: Thu, 23 Jan 2025 13:41:14 -0800
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Rob Clark
	<robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona
 Vetter <simona@...ll.ch>,
        Vinod Koul <vkoul@...nel.org>, Konrad Dybcio
	<konradybcio@...nel.org>
CC: <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 18/35] drm/msm/dpu: get rid of DPU_PINGPONG_DSC



On 1/23/2025 1:32 PM, Abhinav Kumar wrote:
> 
> 
> On 12/13/2024 2:14 PM, Dmitry Baryshkov wrote:
>> Continue migration to the MDSS-revision based checks and replace
>> DPU_PINGPONG_DSC feature bit with the core_major_ver < 7 check.
>>
>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_1_14_msm8937.h |  2 --
>>   drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_1_15_msm8917.h |  1 -
>>   drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_1_16_msm8953.h |  2 --
>>   drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_1_7_msm8996.h  |  6 ++----
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c           | 10 
>> ++--------
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h           |  2 --
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c          |  2 +-
>>   7 files changed, 5 insertions(+), 20 deletions(-)
>>
> 
> <snip>
> 
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c 
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c
>> index 
>> 36c0ec775b92036eaab26e1fa5331579651ac27c..49e03ecee9e8b567a3f809b977deb83731006ac0 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c
>> @@ -319,7 +319,7 @@ struct dpu_hw_pingpong 
>> *dpu_hw_pingpong_init(struct drm_device *dev,
>>           c->ops.disable_autorefresh = dpu_hw_pp_disable_autorefresh;
>>       }
>> -    if (test_bit(DPU_PINGPONG_DSC, &cfg->features)) {
>> +    if (mdss_rev->core_major_ver < 7) {
>>           c->ops.setup_dsc = dpu_hw_pp_setup_dsc;
>>           c->ops.enable_dsc = dpu_hw_pp_dsc_enable;
>>           c->ops.disable_dsc = dpu_hw_pp_dsc_disable;
>>
> 
> So far in this series, we replaced the feature bits with >= checks of 
> core_revisions. That kind of works as usually feature bits get added 
> after a specific version.
> 
> With this patch and later, whenever we use < checks it gets a bit tricky 
> as we might also need an upper bound. Feature bits gave individual 
> control of chipsets but generalizing that all chipsets < 7 have PP DSC 
> is also not correct. I have to really cross-check but there could be 
> some old chipsets which do not have DSC at all.

This raises another question as well.

what if some register was introduced >= X version but was then dropped 
in a newer chipset.

Is it not difficult for the user to go back to the files of each of the 
sub-blocks and alter these checks rather than just fixing up the catalog.