linux-kernel - Re: [PATCH v8 3/4] drm/msm/dpu: revise timing engine programming to support widebus feature

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Date:   Tue, 22 Feb 2022 15:55:32 -0800
From:   Kuogee Hsieh <quic_khsieh@...cinc.com>
To:     Stephen Boyd <swboyd@...omium.org>, <agross@...nel.org>,
        <airlied@...ux.ie>, <bjorn.andersson@...aro.org>,
        <daniel@...ll.ch>, <dmitry.baryshkov@...aro.org>,
        <dri-devel@...ts.freedesktop.org>, <robdclark@...il.com>,
        <sean@...rly.run>, <vkoul@...nel.org>
CC:     <quic_abhinavk@...cinc.com>, <quic_aravindh@...cinc.com>,
        <quic_sbillaka@...cinc.com>, <freedreno@...ts.freedesktop.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 3/4] drm/msm/dpu: revise timing engine programming to
 support widebus feature


On 2/18/2022 6:53 PM, Stephen Boyd wrote:
> Quoting Kuogee Hsieh (2022-02-17 13:36:27)
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> index 0d315b4..0c22839 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> @@ -217,6 +219,14 @@ static u32 dither_matrix[DITHER_MATRIX_SZ] = {
>>          15, 7, 13, 5, 3, 11, 1, 9, 12, 4, 14, 6, 0, 8, 2, 10
>>   };
>>
>> +
>> +bool dpu_encoder_is_widebus_enabled(struct drm_encoder *drm_enc)
> const?
>
>> +{
>> +       struct dpu_encoder_virt *dpu_enc = to_dpu_encoder_virt(drm_enc);
> const?
>
>> +
>> +       return dpu_enc->wide_bus_en;
>> +}
>> +
>>   static void _dpu_encoder_setup_dither(struct dpu_hw_pingpong *hw_pp, unsigned bpc)
>>   {
>>          struct dpu_hw_dither_cfg dither_cfg = { 0 };
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
>> index 99a5d73..893d74d 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
>> @@ -168,4 +168,6 @@ int dpu_encoder_get_linecount(struct drm_encoder *drm_enc);
>>    */
>>   int dpu_encoder_get_frame_count(struct drm_encoder *drm_enc);
>>
>> +bool dpu_encoder_is_widebus_enabled(struct drm_encoder *drm_enc);
> const drm_enc?
>
>> +
>>   #endif /* __DPU_ENCODER_H__ */
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
>> index c2cd185..4e4fa56 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
>> @@ -147,17 +156,36 @@ static void dpu_hw_intf_setup_timing_engine(struct dpu_hw_intf *ctx,
>>          hsync_ctl = (hsync_period << 16) | p->hsync_pulse_width;
>>          display_hctl = (hsync_end_x << 16) | hsync_start_x;
>>
>> -       if (ctx->cap->type == INTF_EDP || ctx->cap->type == INTF_DP) {
>> +       /*
>> +        * DATA_HCTL_EN controls data timing which can be different from
>> +        * video timing. It is recommended to enable it for all cases, except
>> +        * if compression is enabled in 1 pixel per clock mode
>> +        */
>> +       if (p->wide_bus_en)
>> +               intf_cfg2 |= (INTF_CFG2_DATABUS_WIDEN | INTF_CFG2_DATA_HCTL_EN);
> Drop useless parenthesis please.
>
>> +
>> +       data_width = p->width;
>> +
>> +       hsync_data_start_x = hsync_start_x;
>> +       hsync_data_end_x =  hsync_start_x + data_width - 1;
>> +
>> +       display_data_hctl = (hsync_data_end_x << 16) | hsync_data_start_x;
>> +
>> +       if (dp_intf) {
>> +               /* DP timing adjustment */
>> +               display_v_start += p->hsync_pulse_width + p->h_back_porch;
>> +               display_v_end   -= p->h_front_porch;
> Is this code movement intentional?
yes, this timing adjustment is required for DP/eDP
>
>> +
>>                  active_h_start = hsync_start_x;
>>                  active_h_end = active_h_start + p->xres - 1;
>>                  active_v_start = display_v_start;
> display_v_start is different now.
>
>>                  active_v_end = active_v_start + (p->yres * hsync_period) - 1;
>>
>> -               display_v_start += p->hsync_pulse_width + p->h_back_porch;
>> -               display_v_end   -= p->h_front_porch;
>> -
>>                  active_hctl = (active_h_end << 16) | active_h_start;
>>                  display_hctl = active_hctl;
>> +
>> +               intf_cfg |= INTF_CFG_ACTIVE_H_EN;
>> +               intf_cfg |= INTF_CFG_ACTIVE_V_EN;
> 		  intf_cfg |= INTF_CFG_ACTIVE_H_EN | INTF_CFG_ACTIVE_V_EN;
>
> would be one less line.