linux-kernel - Re: [PATCH v2 7/7] drm/msm/dpu: calculate DSC encoder parameters dynamically

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Message-ID: <def3011f-d8e7-3090-47f2-ec13a650337e@quicinc.com>
Date:   Fri, 28 Apr 2023 18:22:25 -0700
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        <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>, <andersson@...nel.org>
CC:     <quic_sbillaka@...cinc.com>, <marijn.suijten@...ainline.org>,
        <freedreno@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 7/7] drm/msm/dpu: calculate DSC encoder parameters
 dynamically



On 4/28/2023 5:52 PM, Dmitry Baryshkov wrote:
> On 29/04/2023 02:45, Kuogee Hsieh wrote:
>> During DSC preparation, add run time calculation to figure out what
>> usage modes, split mode and merge mode, is going to be setup.
> 
> This patch doesn't determine the mode. It changes programming of DSC 
> bits according to the mode being selected.
> 

The term mode is a bit confusing here but he is referring to 
dsc_common_mode.

>>
>> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 56 
>> ++++++++++++++++-------------
>>   1 file changed, 31 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c 
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> index 2fdacf1..3d18642 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> @@ -529,17 +529,9 @@ void dpu_encoder_helper_split_config(
>>   bool dpu_encoder_use_dsc_merge(struct drm_encoder *drm_enc)
>>   {
>>       struct dpu_encoder_virt *dpu_enc = to_dpu_encoder_virt(drm_enc);
>> -    int i, intf_count = 0, num_dsc = 0;
>> +    struct msm_display_topology *topology = &dpu_enc->topology;
>> -    for (i = 0; i < MAX_PHYS_ENCODERS_PER_VIRTUAL; i++)
>> -        if (dpu_enc->phys_encs[i])
>> -            intf_count++;
>> -
>> -    /* See dpu_encoder_get_topology, we only support 2:2:1 topology */
>> -    if (dpu_enc->dsc)
>> -        num_dsc = 2;
>> -
>> -    return (num_dsc > 0) && (num_dsc > intf_count);
>> +    return (topology->num_dsc > topology->num_intf);
>>   }
>>   static void dpu_encoder_get_topology(
>> @@ -1861,41 +1853,55 @@ static void dpu_encoder_prep_dsc(struct 
>> dpu_encoder_virt *dpu_enc,
>>       struct dpu_encoder_phys *enc_master = dpu_enc->cur_master;
>>       struct dpu_hw_dsc *hw_dsc[MAX_CHANNELS_PER_ENC];
>>       struct dpu_hw_pingpong *hw_pp[MAX_CHANNELS_PER_ENC];
>> -    int this_frame_slices;
>> +    struct msm_display_topology *topology = &dpu_enc->topology;
>>       int intf_ip_w, enc_ip_w;
>> -    int dsc_common_mode;
>> -    int pic_width;
>> +    int dsc_common_mode = 0;
> 
> Please don't top-init variables unless required (or unless they are 
> constant).
> 
>>       u32 initial_lines;
>> +    int num_dsc = topology->num_dsc;
>> +    int num_intf = topology->num_intf;
>>       int i;
>> -    for (i = 0; i < MAX_CHANNELS_PER_ENC; i++) {
>> +    for (i = 0; i < num_dsc; i++) {
>>           hw_pp[i] = dpu_enc->hw_pp[i];
>>           hw_dsc[i] = dpu_enc->hw_dsc[i];
>>           if (!hw_pp[i] || !hw_dsc[i]) {
>>               DPU_ERROR_ENC(dpu_enc, "invalid params for DSC\n");
>>               return;
>> -        }
>> +        }
> 
> What is the difference here?
> 
>>       }
>> -    dsc_common_mode = 0;
>> -    pic_width = dsc->pic_width;
>> +    intf_ip_w = dsc->pic_width;
>> -    dsc_common_mode = DSC_MODE_MULTIPLEX | DSC_MODE_SPLIT_PANEL;
>>       if (enc_master->intf_mode == INTF_MODE_VIDEO)
>>           dsc_common_mode |= DSC_MODE_VIDEO;
>> -    this_frame_slices = pic_width / dsc->slice_width;
>> -    intf_ip_w = this_frame_slices * dsc->slice_width;
>> -
>>       /*
>> -     * dsc merge case: when using 2 encoders for the same stream,
>> -     * no. of slices need to be same on both the encoders.
>> +     * If this encoder is driving more than one DSC encoder, they
>> +     * operate in tandem, same pic dimension needs to be used by
>> +     * each of them.(pp-split is assumed to be not supported)
>> +     *
> 
> Extra empty line. Also the comment doesn't make sense here anymore. We 
> already have comment for the division by two below.
> 
>>        */
>> -    enc_ip_w = intf_ip_w / 2;
>> +    enc_ip_w = intf_ip_w;
>> +
>> +    intf_ip_w /= num_intf;
>> +
>> +    if (num_dsc > 1)
>> +        dsc_common_mode |= DSC_MODE_SPLIT_PANEL;
>> +
>> +    if (dpu_encoder_use_dsc_merge(&dpu_enc->base)) {
>> +        dsc_common_mode |= DSC_MODE_MULTIPLEX;
>> +        /*
>> +         * in dsc merge case: when using 2 encoders for the same
>> +         * stream, no. of slices need to be same on both the
>> +         * encoders.
>> +         */
>> +        enc_ip_w = intf_ip_w / 2;
>> +    }
>> +
>>       initial_lines = dpu_encoder_dsc_initial_line_calc(dsc, enc_ip_w);
>> -    for (i = 0; i < MAX_CHANNELS_PER_ENC; i++)
>> +    for (i = 0; i < num_dsc; i++)
>>           dpu_encoder_dsc_pipe_cfg(dpu_enc, hw_dsc[i], hw_pp[i], dsc,
>>                       dsc_common_mode, initial_lines);
>>   }
>