Re: [PATCH 2/2] drm/i915: Parse max HDMI TMDS clock from VBT

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 26 Oct 2017, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Starting from version 204 VBT can specify the max TMDS clock we are
> allowed to use with HDMI ports. Parse that information and take it
> into account when filtering modes and computing a crtc state.
>
> Also take the opportunity to sort the platform check if ladder
> from new to old.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h   |  2 ++
>  drivers/gpu/drm/i915/intel_bios.c | 20 ++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_hdmi.c | 30 ++++++++++++++++++++----------
>  3 files changed, 42 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 366ba74b0ad2..45d32a95ce4a 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1698,6 +1698,8 @@ enum modeset_restore {
>  #define DDC_PIN_D  0x06
>  
>  struct ddi_vbt_port_info {
> +	int max_tmds_clock;
> +
>  	/*
>  	 * This is an index in the HDMI/DVI DDI buffer translation table.
>  	 * The special value HDMI_LEVEL_SHIFT_UNKNOWN means the VBT didn't
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index fd23023df7c1..a0df8e3fefbe 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -1234,6 +1234,26 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
>  		info->hdmi_level_shift = hdmi_level_shift;
>  	}
>  
> +	if (bdb_version >= 204) {
> +		int max_tmds_clock;
> +
> +		switch (child->hdmi_max_data_rate) {
> +		case 1:
> +			max_tmds_clock = 297000;
> +			break;
> +		case 2:
> +			max_tmds_clock = 165000;
> +			break;
> +		default:
> +			max_tmds_clock = 0;

Please add the case values to intel_vbt_defs.h for documentation and
reuse in intel_vbt_decode. Please add debug message about values other
than 0, 1, or 2, i.e. a separate default case with fallback to 0.

With that fixed this is

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

but read on for some comments.

> +			break;
> +		}
> +
> +		DRM_DEBUG_KMS("VBT HDMI max TMDS clock for port %c: %d kHz\n",
> +			      port_name(port), max_tmds_clock);

0 will be most common leading to a funny message...

> +		info->max_tmds_clock = max_tmds_clock;
> +	}
> +
>  	/* Parse the I_boost config for SKL and above */
>  	if (bdb_version >= 196 && child->iboost) {
>  		info->dp_boost_level = translate_iboost(child->dp_iboost_level);
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> index aa486b8925cf..38fe24565b4d 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -1224,24 +1224,34 @@ static void pch_post_disable_hdmi(struct intel_encoder *encoder,
>  	intel_disable_hdmi(encoder, old_crtc_state, old_conn_state);
>  }
>  
> -static int intel_hdmi_source_max_tmds_clock(struct drm_i915_private *dev_priv)
> +static int intel_hdmi_source_max_tmds_clock(struct intel_encoder *encoder)
>  {
> -	if (IS_G4X(dev_priv))
> -		return 165000;
> -	else if (IS_GEMINILAKE(dev_priv))
> -		return 594000;
> -	else if (IS_HASWELL(dev_priv) || INTEL_INFO(dev_priv)->gen >= 8)
> -		return 300000;
> +	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> +	const struct ddi_vbt_port_info *info =
> +		&dev_priv->vbt.ddi_port_info[encoder->port];
> +	int max_tmds_clock;
> +
> +	if (IS_GEMINILAKE(dev_priv))
> +		max_tmds_clock = 594000;

Hmm, are we missing Cannonlake here? If we are, that's a separate patch
anyway.

> +	else if (INTEL_GEN(dev_priv) >= 8 || IS_HASWELL(dev_priv))
> +		max_tmds_clock = 300000;
> +	else if (INTEL_GEN(dev_priv) >= 5)
> +		max_tmds_clock = 225000;
>  	else
> -		return 225000;
> +		max_tmds_clock = 165000;
> +
> +	if (info->max_tmds_clock)
> +		max_tmds_clock = min(max_tmds_clock, info->max_tmds_clock);
> +
> +	return max_tmds_clock;
>  }
>  
>  static int hdmi_port_clock_limit(struct intel_hdmi *hdmi,
>  				 bool respect_downstream_limits,
>  				 bool force_dvi)
>  {
> -	struct drm_device *dev = intel_hdmi_to_dev(hdmi);
> -	int max_tmds_clock = intel_hdmi_source_max_tmds_clock(to_i915(dev));
> +	struct intel_encoder *encoder = &hdmi_to_dig_port(hdmi)->base;
> +	int max_tmds_clock = intel_hdmi_source_max_tmds_clock(encoder);
>  
>  	if (respect_downstream_limits) {
>  		struct intel_connector *connector = hdmi->attached_connector;

-- 
Jani Nikula, Intel Open Source Technology Center
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