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

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Message-ID: <f4884e43-f21e-13a6-65f5-623c101cb823@linaro.org>
Date:   Sat, 29 Apr 2023 04:35:39 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Abhinav Kumar <quic_abhinavk@...cinc.com>,
        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 29/04/2023 04:22, Abhinav Kumar wrote:
> 
> 
> 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.

Yes, that's clear. The patch description is not correct.

> 
>>>
>>> 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);
>>>   }
>>

-- 
With best wishes
Dmitry