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

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Message-ID: <CAE-0n51Rewcp7uefTBJ2HwJN7gp-aTxrWe71XQ-RKosqw8uq8Q@mail.gmail.com>
Date:   Fri, 18 Feb 2022 18:53:44 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>, 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

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?

> +
>                 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.