linux-kernel - Re: [PATCH v4 1/5] drm/msm/dpu: fix video mode DSC for DSI

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Message-ID: <7faghtnpcgrcgxvjo56undtf4un7kcxioxwlif2u63nppl435l@xwwkfxsqimvj>
Date: Fri, 24 May 2024 22:59:51 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Jun Nie <jun.nie@...aro.org>
Cc: Rob Clark <robdclark@...il.com>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Vinod Koul <vkoul@...nel.org>, linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org, Jonathan Marek <jonathan@...ek.ca>
Subject: Re: [PATCH v4 1/5] drm/msm/dpu: fix video mode DSC for DSI

On Fri, May 24, 2024 at 09:18:21PM +0800, Jun Nie wrote:
> From: Jonathan Marek <jonathan@...ek.ca>
> 
> Add necessary DPU timing and control changes for DSC to work with DSI
> video mode.
> 
> Signed-off-by: Jonathan Marek <jonathan@...ek.ca>
> Signed-off-by: Jun Nie <jun.nie@...aro.org>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c          |  2 +-
>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h     |  8 ++++++++
>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c | 13 +++++++++++++
>  drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c          |  4 ++++
>  4 files changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index 119f3ea50a7c..48cef6e79c70 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -564,7 +564,7 @@ bool dpu_encoder_use_dsc_merge(struct drm_encoder *drm_enc)
>  	return (num_dsc > 0) && (num_dsc > intf_count);
>  }
>  
> -static struct drm_dsc_config *dpu_encoder_get_dsc_config(struct drm_encoder *drm_enc)
> +struct drm_dsc_config *dpu_encoder_get_dsc_config(struct drm_encoder *drm_enc)
>  {
>  	struct msm_drm_private *priv = drm_enc->dev->dev_private;
>  	struct dpu_encoder_virt *dpu_enc = to_dpu_encoder_virt(drm_enc);
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h
> index 002e89cc1705..2167c46c1a45 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h
> @@ -334,6 +334,14 @@ static inline enum dpu_3d_blend_mode dpu_encoder_helper_get_3d_blend_mode(
>   */
>  unsigned int dpu_encoder_helper_get_dsc(struct dpu_encoder_phys *phys_enc);
>  
> +/**
> + * dpu_encoder_get_dsc_config - get DSC config for the DPU encoder
> + *   This helper function is used by physical encoder to get DSC config
> + *   used for this encoder.
> + * @drm_enc: Pointer to encoder structure
> + */
> +struct drm_dsc_config *dpu_encoder_get_dsc_config(struct drm_encoder *drm_enc);
> +
>  /**
>   * dpu_encoder_get_drm_fmt - return DRM fourcc format
>   * @phys_enc: Pointer to physical encoder structure
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
> index ef69c2f408c3..7047b607ca91 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
> @@ -115,6 +115,19 @@ static void drm_mode_to_intf_timing_params(
>  		timing->h_front_porch = timing->h_front_porch >> 1;
>  		timing->hsync_pulse_width = timing->hsync_pulse_width >> 1;
>  	}
> +
> +	/*
> +	 * for DSI, if compression is enabled, then divide the horizonal active
> +	 * timing parameters by compression ratio. bits of 3 components(R/G/B)
> +	 * is compressed into bits of 1 pixel.
> +	 */
> +	if (phys_enc->hw_intf->cap->type != INTF_DP && timing->compression_en) {
> +		struct drm_dsc_config *dsc =
> +		       dpu_encoder_get_dsc_config(phys_enc->parent);
> +		timing->width = timing->width * (dsc->bits_per_pixel >> 4) /

Here you are truncating fractional part of BPP. Please use
drm_dsc_get_bpp_int(), at least it will warn if there is a fractional
part. Or, even better, add a helper to calculate width * bpp / 64 / (bpc
* 3) and use it here and in dsi_adjust_pclk_for_compression()

> +				(dsc->bits_per_component * 3);
> +		timing->xres = timing->width;
> +	}
>  }
>  
>  static u32 get_horizontal_total(const struct dpu_hw_intf_timing_params *timing)
> 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 225c1c7768ff..2cf1f8c116b5 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
> @@ -168,6 +168,10 @@ static void dpu_hw_intf_setup_timing_engine(struct dpu_hw_intf *intf,
>  
>  	data_width = p->width;
>  
> +	/* TODO: handle DSC+DP case, we only handle DSC+DSI case so far */
> +	if (p->compression_en && !dp_intf)
> +		intf_cfg2 |= INTF_CFG2_DCE_DATA_COMPRESS;
> +

Separate commit, please

>  	hsync_data_start_x = hsync_start_x;
>  	hsync_data_end_x =  hsync_start_x + data_width - 1;
>  
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry