linux-kernel - Re: [PATCH v3 4/7] drm/msm/dpu: add PINGPONG

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Message-ID: <9e357eff-a649-90cb-0fc2-7ab6a8eb6f19@quicinc.com>
Date:   Wed, 3 May 2023 10:51:47 -0700
From:   Kuogee Hsieh <quic_khsieh@...cinc.com>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
CC:     <dri-devel@...ts.freedesktop.org>, <robdclark@...il.com>,
        <sean@...rly.run>, <swboyd@...omium.org>, <dianders@...omium.org>,
        <vkoul@...nel.org>, <daniel@...ll.ch>, <airlied@...il.com>,
        <agross@...nel.org>, <dmitry.baryshkov@...aro.org>,
        <andersson@...nel.org>, <quic_abhinavk@...cinc.com>,
        <quic_sbillaka@...cinc.com>, <freedreno@...ts.freedesktop.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 4/7] drm/msm/dpu: add PINGPONG_NONE to disconnect DSC
 from PINGPONG


On 5/3/2023 1:03 AM, Marijn Suijten wrote:
> On 2023-05-02 14:02:59, Kuogee Hsieh wrote:
>> During DSC setup, the crossbar mux need to be programmed to engage
>> DSC to specified PINGPONG. Hence during tear down, the crossbar mux
>> need to be reset to disengage DSC from PINGPONG. This patch add
>> PINGPONG_NONE to serve as disable to reset crossbar mux.
> This patch doesn't *just add* PINGPONG_NONE to reset the crossbar; that
> functionality was already available thanks to a `bool enable` function
> parameter.  Instead it should explain why you think PINGPONG_NONE is
> more convenient than passing a bool that warrants this replacement.
> (Hint: I think because you don't have a hw_pp->idx available in the
>   teardown path, and/or its value is not relevant for the disable case
>   anyway.)
>
> In addition I don't see this series use PINGPONG_NONE anywhere yet: will
> that be added in the DSC 1.2 series for DP (to support hotplug)?

PINGPONG_NONE will be used to tear down DSC data path later at DP DSC 
patch series.

Current it is not used because DSI does not do tear down.

>
>> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 2 +-
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c  | 7 +++----
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.h  | 1 -
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h | 3 ++-
>>   4 files changed, 6 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> index 1dc5dbe..d9ad334 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> @@ -1839,7 +1839,7 @@ static void dpu_encoder_dsc_pipe_cfg(struct dpu_hw_dsc *hw_dsc,
>>   		hw_pp->ops.setup_dsc(hw_pp);
>>   
>>   	if (hw_dsc->ops.dsc_bind_pingpong_blk)
>> -		hw_dsc->ops.dsc_bind_pingpong_blk(hw_dsc, true, hw_pp->idx);
>> +		hw_dsc->ops.dsc_bind_pingpong_blk(hw_dsc, hw_pp->idx);
>>   
>>   	if (hw_pp->ops.enable_dsc)
>>   		hw_pp->ops.enable_dsc(hw_pp);
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c
>> index 4a6bbcc..3e68d47 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c
>> @@ -157,7 +157,6 @@ static void dpu_hw_dsc_config_thresh(struct dpu_hw_dsc *hw_dsc,
>>   
>>   static void dpu_hw_dsc_bind_pingpong_blk(
>>   		struct dpu_hw_dsc *hw_dsc,
>> -		bool enable,
>>   		const enum dpu_pingpong pp)
>>   {
>>   	struct dpu_hw_blk_reg_map *c = &hw_dsc->hw;
>> @@ -166,13 +165,13 @@ static void dpu_hw_dsc_bind_pingpong_blk(
>>   
>>   	dsc_ctl_offset = DSC_CTL(hw_dsc->idx);
>>   
>> -	if (enable)
>> +	if (pp)
>>   		mux_cfg = (pp - PINGPONG_0) & 0x7;
>>   
>>   	DRM_DEBUG_KMS("%s dsc:%d %s pp:%d\n",
>> -			enable ? "Binding" : "Unbinding",
>> +			pp ? "Binding" : "Unbinding",
>>   			hw_dsc->idx - DSC_0,
>> -			enable ? "to" : "from",
>> +			pp ? "to" : "from",
>>   			pp - PINGPONG_0);
> PINGPONG_NONE - PINGPONG_0 = -1, so this whole debug log likely needs to
> be rewritten for the disable case as we don't know what PINGPONG it is
> being unbound from.  How about:
>
> 	if (pp)
> 		DRM_DEBUG_KMS("Binding dsc:%d to pp:%d\n",
> 				hw_dsc->idx - DSC_0,
> 				pp - PINGPONG_0);
> 	else
> 		DRM_DEBUG_KMS("Unbinding dsc:%d from any pp\n",
> 				hw_dsc->idx - DSC_0);
>
> - Marijn
>
>>   
>>   	DPU_REG_WRITE(c, dsc_ctl_offset, mux_cfg);
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.h
>> index 287ec5f..138080a 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.h
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.h
>> @@ -44,7 +44,6 @@ struct dpu_hw_dsc_ops {
>>   				  struct drm_dsc_config *dsc);
>>   
>>   	void (*dsc_bind_pingpong_blk)(struct dpu_hw_dsc *hw_dsc,
>> -				  bool enable,
>>   				  enum dpu_pingpong pp);
>>   };
>>   
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h
>> index 2d9192a..56826a9 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h
>> @@ -191,7 +191,8 @@ enum dpu_dsc {
>>   };
>>   
>>   enum dpu_pingpong {
>> -	PINGPONG_0 = 1,
>> +	PINGPONG_NONE,
>> +	PINGPONG_0,
>>   	PINGPONG_1,
>>   	PINGPONG_2,
>>   	PINGPONG_3,
>> -- 
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>> a Linux Foundation Collaborative Project
>>