Re: [PATCH 5/6] drm/i915: enable scrambling

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

On Wed, Feb 01, 2017 at 06:14:40PM +0530, Shashank Sharma wrote:
> Geminilake platform has a native HDMI 2.0 controller, and is
> capable of driving pixel-clocks upto 594Mhz. HDMI 2.0 spec
> mendates scrambling for these higher clocks, for reduced RF footprint.
> 
> This patch checks if the monitor supports scrambling, and if required,
> enables it during the modeset.
> 
> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h   |  2 ++
>  drivers/gpu/drm/i915/intel_ddi.c  |  5 +++++
>  drivers/gpu/drm/i915/intel_drv.h  |  2 ++
>  drivers/gpu/drm/i915/intel_hdmi.c | 42 +++++++++++++++++++++++++++++++++++++++
>  4 files changed, 51 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 495b789..cc85892 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7807,6 +7807,8 @@ enum {
>  #define  TRANS_DDI_EDP_INPUT_C_ONOFF	(6<<12)
>  #define  TRANS_DDI_DP_VC_PAYLOAD_ALLOC	(1<<8)
>  #define  TRANS_DDI_BFI_ENABLE		(1<<4)
> +#define  TRANS_DDI_HIGH_TMDS_CHAR_RATE	(1<<4)
> +#define  TRANS_DDI_HDMI_SCRAMBLING	(1<<0)
>  
>  /* DisplayPort Transport Control */
>  #define _DP_TP_CTL_A			0x64040
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index 9a9a670..aea81ce 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -1278,6 +1278,11 @@ void intel_ddi_enable_transcoder_func(struct drm_crtc *crtc)
>  			temp |= TRANS_DDI_MODE_SELECT_HDMI;
>  		else
>  			temp |= TRANS_DDI_MODE_SELECT_DVI;
> +
> +		if (IS_GEMINILAKE(dev_priv)) {
> +			temp |= intel_hdmi_check_scrambling(intel_encoder,
> +				&intel_crtc->config->base.adjusted_mode);
> +		}
>  	} else if (type == INTEL_OUTPUT_ANALOG) {
>  		temp |= TRANS_DDI_MODE_SELECT_FDI;
>  		temp |= (intel_crtc->config->fdi_lanes - 1) << 1;
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 393f243..aafce7f 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1588,6 +1588,8 @@ void intel_hdmi_init_connector(struct intel_digital_port *intel_dig_port,
>  bool intel_hdmi_compute_config(struct intel_encoder *encoder,
>  			       struct intel_crtc_state *pipe_config,
>  			       struct drm_connector_state *conn_state);
> +uint32_t intel_hdmi_check_scrambling(struct intel_encoder *intel_encoder,
> +				struct drm_display_mode *mode);
>  void intel_dp_dual_mode_set_tmds_output(struct intel_hdmi *hdmi, bool enable);
>  
>  
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> index ebae2bd..92dd9bc 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -1795,6 +1795,48 @@ static void intel_hdmi_destroy(struct drm_connector *connector)
>  	intel_hdmi->aspect_ratio = HDMI_PICTURE_ASPECT_NONE;
>  }
>  
> +static void
> +intel_hdmi_enable_scrambling(struct drm_connector *connector)
> +{
> +	struct drm_i915_private *dev_priv = connector->dev->dev_private;
> +	struct intel_hdmi *intel_hdmi = intel_attached_hdmi(connector);
> +	struct i2c_adapter *adapter =
> +			intel_gmbus_get_adapter(dev_priv, intel_hdmi->ddc_bus);
> +
> +	if (!drm_enable_scrambling(connector, adapter, true))
> +		DRM_ERROR("Request to enable scrambling failed\n");
> +}

I don't like hiding this somewhere deep like this. It should be
somewhere much higher up.

And I'm thinkign we might want to track the scrambler state
in the crtc state.

> +
> +uint32_t intel_hdmi_check_scrambling(struct intel_encoder *intel_encoder,
> +				struct drm_display_mode *mode)
> +{
> +	struct intel_hdmi *intel_hdmi = enc_to_intel_hdmi(&intel_encoder->base);
> +	struct drm_connector *connector = &intel_hdmi->attached_connector->base;
> +	struct drm_hdmi_info *hdmi_info = &connector->display_info.hdmi_info;
> +	uint32_t hdmi_config = 0;
> +
> +	DRM_DEBUG_KMS("Checking scrambling for enc:%s connector:%s\n",
> +			intel_encoder->base.name, connector->name);
> +
> +	if (mode->clock < 340000) {
> +		if (hdmi_info->scr_info.low_clocks) {
> +			intel_hdmi_enable_scrambling(connector);
> +			hdmi_config |= TRANS_DDI_HDMI_SCRAMBLING;
> +		}
> +		return hdmi_config;
> +	}
> +
> +	/* Enable scrambling for clocks > 340M */
> +	if (hdmi_info->scr_info.supported) {
> +		intel_hdmi_enable_scrambling(connector);
> +		hdmi_config |= TRANS_DDI_HDMI_SCRAMBLING;
> +	}
> +
> +	/* Scrambling or not, if clock > 340M, set high char rate */
> +	hdmi_config |= TRANS_DDI_HIGH_TMDS_CHAR_RATE;
> +	return hdmi_config;
> +}
> +
>  static u8 intel_hdmi_ddc_pin(struct drm_i915_private *dev_priv,
>  			     enum port port)
>  {
> -- 
> 1.9.1

-- 
Ville Syrjälä
Intel OTC
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