linux-kernel - Re: [Freedreno] [PATCH v3] drm/msm/dpu: always program DSC active bits

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Message-ID: <51d953d0-bd7f-1154-0241-89a2f62967e4@linaro.org>
Date:   Thu, 20 Apr 2023 19:41:30 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc:     freedreno@...ts.freedesktop.org, quic_sbillaka@...cinc.com,
        airlied@...il.com, andersson@...nel.org, robdclark@...il.com,
        dri-devel@...ts.freedesktop.org, dianders@...omium.org,
        vkoul@...nel.org, agross@...nel.org, daniel@...ll.ch,
        linux-arm-msm@...r.kernel.org, swboyd@...omium.org,
        sean@...rly.run, linux-kernel@...r.kernel.org
Subject: Re: [Freedreno] [PATCH v3] drm/msm/dpu: always program DSC active
 bits

On 20/04/2023 19:40, Abhinav Kumar wrote:
> Hi Dmitry / Marijn
> 
> On 4/20/2023 7:03 AM, Dmitry Baryshkov wrote:
>> On 15/04/2023 02:02, Marijn Suijten wrote:
>>> On 2023-04-14 09:46:17, Kuogee Hsieh wrote:
>>>> In current code, the dsc active bits are set only if the cfg->dsc is 
>>>> set.
>>>
>>> This is the old sentence from v1 again, did you accidentally send the
>>> wrong patch as the improvements from v2 are missing?
>>>
>>>> However, for displays which are hot-pluggable, there can be a use-case
>>>> of disconnecting a DSC supported sink and connecting a non-DSC sink.
>>>>
>>>> For those cases we need to clear DSC active bits during teardown.
>>>
>>> At least teardown is one word again, v2 had "tear down" which is wrong.
>>>
>>>> As discuss at [1], clear DSC active bit will handled at 
>>>> reset_intf_cfg()
>>>
>>> discussed* as pointed out by Dmitry, and make it clear that this is
>>> about clearing CTL_DSC_ACTIVE (and CTL_DSC_FLUSH?) specifically.  Once
>>> that is moved to reset_intf_cfg(), this patch should be reverted as
>>> there is no need to write the registers once again when cfg->dsc equals
>>> 0.
>>
>> Kuogee, can we please get a proper v4? With all the relevant changes 
>> from v2, with the changelog, etc.
>>
>> Otherwise the present Reviewed-by tags are just incorrect.
>>
> 
> After looking into the DPU DSC changes internally which will be posted 
> today/tomm, that piece of code is again touching this block, so I am now 
> also not convinced this change should be made right now because it was 
> again touching flush programming, so that again leaves only the active 
> bits which as Marijn mentioned will be applicable for a use-case only 
> with hot-pluggable display which we dont have till we land DP DSC.
> 
> I think this is what we will do:
> 
> -> post DPU DSC changes
> -> post the patch to improve reset_intf_cfg() to handle DSC
> -> post rest of DP DSC changes
> -> post rest of DSI DSC changes
> 
> I think that way, we all are aligned.
> 
> Apologies for posting this patch a bit ahead of time but if i had 
> foreseen that DPU DSC changes will again touch the flush code, i would 
> have held this patch back too.

Ack, sounds good. Thank you.

> 
>>>
>>> - Marijn
>>>
>>>> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
>>>> Fixes: 77f6da90487c ("drm/msm/disp/dpu1: Add DSC support in hw_ctl")
>>>> Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
>>>> Reviewed-by: Marijn Suijten <marijn.suijten@...ainline.org>
>>>>
>>>> [1] 
>>>> https://lore.kernel.org/linux-arm-msm/ec045d6b-4ffd-0f8c-4011-8db45edc6978@quicinc.com/
>>>> ---
>>>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c | 7 +++----
>>>>   1 file changed, 3 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c 
>>>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c
>>>> index bbdc95c..88e4efe 100644
>>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c
>>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c
>>>> @@ -541,10 +541,9 @@ static void dpu_hw_ctl_intf_cfg_v1(struct 
>>>> dpu_hw_ctl *ctx,
>>>>       if (cfg->merge_3d)
>>>>           DPU_REG_WRITE(c, CTL_MERGE_3D_ACTIVE,
>>>>                     BIT(cfg->merge_3d - MERGE_3D_0));
>>>> -    if (cfg->dsc) {
>>>> -        DPU_REG_WRITE(&ctx->hw, CTL_FLUSH, DSC_IDX);
>>>> -        DPU_REG_WRITE(c, CTL_DSC_ACTIVE, cfg->dsc);
>>>> -    }
>>>> +
>>>> +    DPU_REG_WRITE(&ctx->hw, CTL_FLUSH, DSC_IDX);
>>>> +    DPU_REG_WRITE(c, CTL_DSC_ACTIVE, cfg->dsc);
>>>>   }
>>>>   static void dpu_hw_ctl_intf_cfg(struct dpu_hw_ctl *ctx,
>>>> -- 
>>>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>>>> Forum,
>>>> a Linux Foundation Collaborative Project
>>>>
>>

-- 
With best wishes
Dmitry