Re: [PATCH v12 8/8] drm/i915: Add YCBCR 4:2:0/4:4:4 support for LSPCON

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Oct 12, 2018 at 11:53:14AM +0530, Shashank Sharma wrote:
> From: Shashank Sharma <shashank.sharma@linux.intel.com>
> 
> LSPCON chips can generate YCBCR outputs, if asked nicely :).
> 
> In order to generate YCBCR 4:2:0 outputs, a source must:
> - send YCBCR 4:4:4 signals to LSPCON
> - program color space as 4:2:0 in AVI infoframes
> 
> Whereas for YCBCR 4:4:4 outputs, the source must:
> - send YCBCR 4:4:4 signals to LSPCON
> - program color space as 4:4:4 in AVI infoframes
> 
> So for both 4:2:0 as well as 4:4:4 outputs, we are driving the
> pipe for YCBCR 4:4:4 output, but AVI infoframe's color space
> information indicates LSPCON FW to start scaling down from YCBCR
> 4:4:4 and generate YCBCR 4:2:0 output. As the scaling is done by
> LSPCON device, we need not to reserve a scaler for 4:2:0 outputs.
> 
> V2: rebase
> V3: Addressed review comments from Ville
>     - add enum crtc_output_format instead of bool ycbcr420
>     - use crtc_output_format=4:4:4 for modeset of LSPCON 4:2:0 output
>       cases in this way we will have YCBCR 4:4:4 framework ready (except
>       the ABI part)
> V4: Added r-b from Maarten (for v3)
>     Addressed review comments from Ville:
>     - Do not add a non-atomic state variable to determine lspcon output.
>       Instead add bool in CRTC state to indicate lspcon based scaling.
> V5: Addressed review comments from Ville:
>     - Change the state bool name from external scaling to something more
>       relavent.
>     - Keep the info and adjusted_mode structures const.
>     - use crtc_state instead of pipe_config.
>     - Push all the config change into lspcon_ycbcr420_config function.
> V6: Rebase, small changes to accommodate changes in patch 2.
> V7: Fixed checkpatch warnings for alignment
> V8: Rebase
> 
>     PS: Ignored following warnings to match the current formatting:
>     drm/i915: Add YCBCR 4:2:0/4:4:4 support for LSPCON
>      -:53: CHECK:SPACING: spaces preferred around that '<<' (ctx:VxV)
>     #53: FILE: drivers/gpu/drm/i915/i915_reg.h:8721:
>     +#define  TRANS_MSA_SAMPLING_444        (2<<1)
>                                           ^
>     -:54: CHECK:SPACING: spaces preferred around that '<<' (ctx:VxV)
>     #54: FILE: drivers/gpu/drm/i915/i915_reg.h:8722:
>     +#define  TRANS_MSA_CLRSP_YCBCR         (2<<3)
> V9: Rebase
> V10: Rebase
> V11: Rebase
> 
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h      |  2 ++
>  drivers/gpu/drm/i915/intel_ddi.c     |  7 +++++++
>  drivers/gpu/drm/i915/intel_display.c | 12 ++++++++++++
>  drivers/gpu/drm/i915/intel_dp.c      |  4 ++++
>  drivers/gpu/drm/i915/intel_drv.h     |  5 +++++
>  drivers/gpu/drm/i915/intel_lspcon.c  | 26 ++++++++++++++++++++++++++
>  6 files changed, 56 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 2078541..1e13e51 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -9229,6 +9229,8 @@ enum skl_power_gate {
>  #define TRANS_MSA_MISC(tran) _MMIO_TRANS2(tran, _TRANSA_MSA_MISC)
>  
>  #define  TRANS_MSA_SYNC_CLK		(1 << 0)
> +#define  TRANS_MSA_SAMPLING_444		(2 << 1)
> +#define  TRANS_MSA_CLRSP_YCBCR		(2 << 3)
>  #define  TRANS_MSA_6_BPC		(0 << 5)
>  #define  TRANS_MSA_8_BPC		(1 << 5)
>  #define  TRANS_MSA_10_BPC		(2 << 5)
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index be21131..186111a 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -1784,6 +1784,13 @@ void intel_ddi_set_pipe_settings(const struct intel_crtc_state *crtc_state)
>  		break;
>  	}
>  
> +	/*
> +	 * As per DP 1.2 spec section 2.3.4.3 while sending
> +	 * YCBCR 444 signals we should program MSA MISC1/0 fields with
> +	 * colorspace information. The output colorspace encoding is BT601.
> +	 */
> +	if (crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR444)
> +		temp |= TRANS_MSA_SAMPLING_444 | TRANS_MSA_CLRSP_YCBCR;
>  	I915_WRITE(TRANS_MSA_MISC(cpu_transcoder), temp);
>  }
>  
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 3317c6c..41abd03 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -7797,6 +7797,8 @@ static void intel_get_crtc_ycbcr_config(struct intel_crtc *crtc,
>  	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
>  	enum intel_output_format output = INTEL_OUTPUT_FORMAT_RGB;
>  
> +	pipe_config->lspcon_downsampling = false;
> +
>  	if (IS_BROADWELL(dev_priv) || INTEL_GEN(dev_priv) >= 9) {
>  		u32 tmp = I915_READ(PIPEMISC(crtc->pipe));
>  
> @@ -7814,6 +7816,16 @@ static void intel_get_crtc_ycbcr_config(struct intel_crtc *crtc,
>  				else
>  					output = INTEL_OUTPUT_FORMAT_YCBCR420;
>  			} else {
> +				/*
> +				 * Currently there is no interface defined to
> +				 * check user preference between RGB/YCBCR444
> +				 * or YCBCR420. So the only possible case for
> +				 * YCBCR444 usage is driving YCBCR420 output
> +				 * with LSPCON, when pipe is configured for
> +				 * YCBCR444 output and LSPCON takes care of
> +				 * downsampling it.
> +				 */
> +				pipe_config->lspcon_downsampling = true;
>  				output = INTEL_OUTPUT_FORMAT_YCBCR444;
>  			}
>  		}
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index c3f6330..1156d59 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -2074,6 +2074,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
>  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
>  	struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
>  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> +	struct intel_lspcon *lspcon = enc_to_intel_lspcon(&encoder->base);
>  	enum port port = encoder->port;
>  	struct intel_crtc *intel_crtc = to_intel_crtc(pipe_config->base.crtc);
>  	struct intel_connector *intel_connector = intel_dp->attached_connector;
> @@ -2086,6 +2087,9 @@ intel_dp_compute_config(struct intel_encoder *encoder,
>  		pipe_config->has_pch_encoder = true;
>  
>  	pipe_config->output_format = INTEL_OUTPUT_FORMAT_RGB;
> +	if (lspcon->active)
> +		lspcon_ycbcr420_config(&intel_connector->base, pipe_config);
> +
>  	pipe_config->has_drrs = false;
>  	if (IS_G4X(dev_priv) || port == PORT_A)
>  		pipe_config->has_audio = false;
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index b8e5f95..95e252e 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -908,6 +908,9 @@ struct intel_crtc_state {
>  
>  	/* Output format RGB/YCBCR etc */
>  	enum intel_output_format output_format;
> +
> +	/* Output down scaling is done in LSPCON device */
> +	bool lspcon_downsampling;
>  };
>  
>  struct intel_crtc {
> @@ -2225,6 +2228,8 @@ void lspcon_set_infoframes(struct intel_encoder *encoder,
>  			   const struct drm_connector_state *conn_state);
>  bool lspcon_infoframe_enabled(struct intel_encoder *encoder,
>  			      const struct intel_crtc_state *pipe_config);
> +void lspcon_ycbcr420_config(struct drm_connector *connector,
> +			    struct intel_crtc_state *crtc_state);
>  
>  /* intel_pipe_crc.c */
>  #ifdef CONFIG_DEBUG_FS
> diff --git a/drivers/gpu/drm/i915/intel_lspcon.c b/drivers/gpu/drm/i915/intel_lspcon.c
> index 829c40a..fff32b3 100644
> --- a/drivers/gpu/drm/i915/intel_lspcon.c
> +++ b/drivers/gpu/drm/i915/intel_lspcon.c
> @@ -180,6 +180,21 @@ static bool lspcon_wake_native_aux_ch(struct intel_lspcon *lspcon)
>  	return true;
>  }
>  
> +void lspcon_ycbcr420_config(struct drm_connector *connector,
> +			    struct intel_crtc_state *crtc_state)
> +{
> +	const struct drm_display_info *info = &connector->display_info;
> +	const struct drm_display_mode *adjusted_mode =
> +					&crtc_state->base.adjusted_mode;
> +
> +	if (drm_mode_is_420_only(info, adjusted_mode) &&
> +	    connector->ycbcr_420_allowed) {
> +		crtc_state->port_clock /= 2;

This looks bogus. We're talking about DP here so we should not be
frobbing port_clock. And since we output 4:4:4 from the port
anyway we don't even have to take 4:2:0 into consideration
when calculating port_clock.

Ah, this guy is called before we even calculate port_clock.
That explains why this didn't cause any problems. So this is
just dead code here.

And looks like the port_clock adjustment in intel_hdmi_ycbcr420_config() 
also dead code since the caller overwrites it there as well.

> +		crtc_state->output_format = INTEL_OUTPUT_FORMAT_YCBCR444;
> +		crtc_state->lspcon_downsampling = true;
> +	}
> +}
> +
>  static bool lspcon_probe(struct intel_lspcon *lspcon)
>  {
>  	int retry;
> @@ -464,6 +479,15 @@ void lspcon_set_infoframes(struct intel_encoder *encoder,
>  		return;
>  	}
>  
> +	if (crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR444) {
> +		if (crtc_state->lspcon_downsampling)
> +			frame.avi.colorspace = HDMI_COLORSPACE_YUV420;
> +		else
> +			frame.avi.colorspace = HDMI_COLORSPACE_YUV444;
> +	} else {
> +		frame.avi.colorspace = HDMI_COLORSPACE_RGB;
> +	}
> +
>  	drm_hdmi_avi_infoframe_quant_range(&frame.avi, mode,
>  					   crtc_state->limited_color_range ?
>  					   HDMI_QUANTIZATION_RANGE_LIMITED :
> @@ -517,6 +541,7 @@ bool lspcon_init(struct intel_digital_port *intel_dig_port)
>  	struct intel_lspcon *lspcon = &intel_dig_port->lspcon;
>  	struct drm_device *dev = intel_dig_port->base.base.dev;
>  	struct drm_i915_private *dev_priv = to_i915(dev);
> +	struct drm_connector *connector = &dp->attached_connector->base;
>  
>  	if (!HAS_LSPCON(dev_priv)) {
>  		DRM_ERROR("LSPCON is not supported on this platform\n");
> @@ -541,6 +566,7 @@ bool lspcon_init(struct intel_digital_port *intel_dig_port)
>  		return false;
>  	}
>  
> +	connector->ycbcr_420_allowed = true;
>  	lspcon->active = true;
>  	DRM_DEBUG_KMS("Success: LSPCON init\n");
>  	return true;
> -- 
> 2.7.4

-- 
Ville Syrjälä
Intel
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