Re: [5/7] drm/i915/dp: Enable AUX based backlight for HDR

[Sebastian Wick <sebastian.wick@redhat.com>]

On Thu, Apr 04, 2024 at 08:59:29AM +0530, Suraj Kandpal wrote:
> As of now whenerver HDR is switched on we use the PWM to change the
> backlight as opposed to AUX based backlight changes in terms of nits.
> This patch writes to the appropriate DPCD registers to enable aux
> based backlight using values in nits.
> 
> --v2
> -Fix max_cll and max_fall assignment [Jani]
> -Fix the size sent in drm_dpcd_write [Jani]
> 
> --v3
> -Content Luminance needs to be sent only for pre-ICL after that
> it is directly picked up from hdr metadata [Ville]
> 
> --v4
> -Add checks for HDR TCON cap bits [Ville]
> -Check eotf of hdr_output_data and sets bits base of that value.
> 
> --v5
> -Fix capability check bits.
> -Check colorspace before setting BT2020
> 
> --v6
> -Use intel_dp_has_gamut_dip to check if we have capability
> to send sdp [Ville]
> -Seprate filling of all hdr tcon related bits into it's
> own function.
> -Check eotf data to make sure we are in HDR mode [Sebastian]
> 
> Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
> ---
>  .../drm/i915/display/intel_dp_aux_backlight.c | 105 ++++++++++++++++--
>  1 file changed, 94 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> index 2d50a4734823..7af876e2d210 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -40,11 +40,6 @@
>  #include "intel_dp.h"
>  #include "intel_dp_aux_backlight.h"
>  
> -/* TODO:
> - * Implement HDR, right now we just implement the bare minimum to bring us back into SDR mode so we
> - * can make people's backlights work in the mean time
> - */
> -
>  /*
>   * DP AUX registers for Intel's proprietary HDR backlight interface. We define
>   * them here since we'll likely be the only driver to ever use these.
> @@ -127,9 +122,6 @@ intel_dp_aux_supports_hdr_backlight(struct intel_connector *connector)
>  	if (ret != sizeof(tcon_cap))
>  		return false;
>  
> -	if (!(tcon_cap[1] & INTEL_EDP_HDR_TCON_BRIGHTNESS_NITS_CAP))
> -		return false;
> -
>  	drm_dbg_kms(&i915->drm, "[CONNECTOR:%d:%s] Detected %s HDR backlight interface version %d\n",
>  		    connector->base.base.id, connector->base.name,
>  		    is_intel_tcon_cap(tcon_cap) ? "Intel" : "unsupported", tcon_cap[0]);
> @@ -137,6 +129,9 @@ intel_dp_aux_supports_hdr_backlight(struct intel_connector *connector)
>  	if (!is_intel_tcon_cap(tcon_cap))
>  		return false;
>  
> +	if (!(tcon_cap[1] & INTEL_EDP_HDR_TCON_BRIGHTNESS_NITS_CAP))
> +		return false;
> +
>  	/*
>  	 * If we don't have HDR static metadata there is no way to
>  	 * runtime detect used range for nits based control. For now
> @@ -225,13 +220,27 @@ intel_dp_aux_hdr_set_aux_backlight(const struct drm_connector_state *conn_state,
>  			connector->base.base.id, connector->base.name);
>  }
>  
> +static bool
> +intel_dp_aux_in_hdr_mode(const struct drm_connector_state *conn_state)
> +{
> +	struct hdr_output_metadata *hdr_metadata;
> +
> +	if (!conn_state->hdr_output_metadata)
> +		return false;
> +
> +	hdr_metadata = conn_state->hdr_output_metadata->data;
> +
> +	return hdr_metadata->hdmi_metadata_type1.eotf != HDMI_EOTF_TRADITIONAL_GAMMA_SDR;

This line worries me a bit. The TCON only supports PQ HDR mode so when
the metadata request HLG or traditional gamma HDR then only the
segmented backlight is enable in intel_dp_aux_fill_hdr_tcon_params but
it uses HDR backlight.

Did you test that this doesn't result in a black screen? Maybe change
this to `eotf == HDMI_EOTF_SMPTE_ST2084` instead?

> +}
> +
>  static void
>  intel_dp_aux_hdr_set_backlight(const struct drm_connector_state *conn_state, u32 level)
>  {
>  	struct intel_connector *connector = to_intel_connector(conn_state->connector);
>  	struct intel_panel *panel = &connector->panel;
>  
> -	if (panel->backlight.edp.intel.sdr_uses_aux) {
> +	if (intel_dp_aux_in_hdr_mode(conn_state) ||
> +	    panel->backlight.edp.intel.sdr_uses_aux) {
>  		intel_dp_aux_hdr_set_aux_backlight(conn_state, level);
>  	} else {
>  		const u32 pwm_level = intel_backlight_level_to_pwm(connector, level);
> @@ -240,6 +249,70 @@ intel_dp_aux_hdr_set_backlight(const struct drm_connector_state *conn_state, u32
>  	}
>  }
>  
> +static void
> +intel_dp_aux_write_content_luminance(struct intel_connector *connector,
> +				     struct hdr_output_metadata *hdr_metadata)
> +{
> +	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
> +	struct drm_i915_private *i915 = to_i915(connector->base.dev);
> +	int ret;
> +	u8 buf[4];
> +
> +	if (!intel_dp_has_gamut_metadata_dip(connector->encoder))
> +		return;

I don't entirely understand intel_dp_has_gamut_metadata_dip, but I
assume it is true when the SDP HDR stuff can be send?

Either way, you only enable the HDR_OUTPUT_METADATA property if
intel_dp_has_gamut_metadata_dip returns true, so you will only ever have
intel_dp_aux_in_hdr_mode return true if the dip exists. So, this doesn't
do anything.

I think what you need is

* attach the HDR_OUTPUT_METADATA property if you can send the SDP thing
  and the TCON supports the SDP override (>ICL) OR you can control HDR
  via AUX (>=ICL).
* always set the content luminance via AUX

> +
> +	buf[0] = hdr_metadata->hdmi_metadata_type1.max_cll & 0xFF;
> +	buf[1] = (hdr_metadata->hdmi_metadata_type1.max_cll & 0xFF00) >> 8;
> +	buf[2] = hdr_metadata->hdmi_metadata_type1.max_fall & 0xFF;
> +	buf[3] = (hdr_metadata->hdmi_metadata_type1.max_fall & 0xFF00) >> 8;
> +
> +	ret = drm_dp_dpcd_write(&intel_dp->aux,
> +				INTEL_EDP_HDR_CONTENT_LUMINANCE,
> +				buf, sizeof(buf));
> +	if (ret < 0)
> +		drm_dbg_kms(&i915->drm,
> +			    "Content Luminance DPCD reg write failed, err:-%d\n",
> +			    ret);
> +}
> +
> +static void
> +intel_dp_aux_fill_hdr_tcon_params(const struct drm_connector_state *conn_state, u8 *ctrl)
> +{
> +	struct intel_connector *connector = to_intel_connector(conn_state->connector);
> +	struct intel_panel *panel = &connector->panel;
> +	struct drm_i915_private *i915 = to_i915(connector->base.dev);
> +	struct hdr_output_metadata *hdr_metadata = conn_state->hdr_output_metadata->data;
> +
> +	/* According to spec segmented backlight needs to be set whenever panel is in
> +	 * HDR mode.
> +	 */
> +	*ctrl |= INTEL_EDP_HDR_TCON_SEGMENTED_BACKLIGHT_ENABLE;
> +
> +	/* 2084 decode needs to set if eotf suggests so or in case of pre-ICL we disable
> +	 * tone mapping and set 2084 decode.
> +	 */
> +	if (hdr_metadata->hdmi_metadata_type1.eotf ==
> +	    HDMI_EOTF_SMPTE_ST2084 || DISPLAY_VER(i915) < 11) {
> +		*ctrl |= INTEL_EDP_HDR_TCON_2084_DECODE_ENABLE;
> +		*ctrl &= ~INTEL_EDP_HDR_TCON_TONE_MAPPING_ENABLE;
> +	} else {
> +		drm_dbg_kms(&i915->drm, "[CONNECTOR:%d:%s] TCON: Cannot decode requested EOTF\n",
> +			    connector->base.base.id, connector->base.name);
> +	}
> +
> +	if (panel->backlight.edp.intel.supports_2020_gamut &&
> +	    (conn_state->colorspace == DRM_MODE_COLORIMETRY_BT2020_RGB ||
> +	     conn_state->colorspace == DRM_MODE_COLORIMETRY_BT2020_YCC ||
> +	     conn_state->colorspace == DRM_MODE_COLORIMETRY_BT2020_CYCC))
> +		*ctrl |= INTEL_EDP_HDR_TCON_2020_GAMUT_ENABLE;
> +
> +	if (panel->backlight.edp.intel.supports_sdp_colorimetry &&
> +	    intel_dp_has_gamut_metadata_dip(connector->encoder))
> +		*ctrl |= INTEL_EDP_HDR_TCON_SDP_OVERRIDE_AUX;
> +	else
> +		*ctrl &= ~INTEL_EDP_HDR_TCON_SDP_OVERRIDE_AUX;
> +}
> +
>  static void
>  intel_dp_aux_hdr_enable_backlight(const struct intel_crtc_state *crtc_state,
>  				  const struct drm_connector_state *conn_state, u32 level)
> @@ -248,6 +321,7 @@ intel_dp_aux_hdr_enable_backlight(const struct intel_crtc_state *crtc_state,
>  	struct intel_panel *panel = &connector->panel;
>  	struct drm_i915_private *i915 = to_i915(connector->base.dev);
>  	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
> +	struct hdr_output_metadata *hdr_metadata;
>  	int ret;
>  	u8 old_ctrl, ctrl;
>  
> @@ -261,8 +335,10 @@ intel_dp_aux_hdr_enable_backlight(const struct intel_crtc_state *crtc_state,
>  	}
>  
>  	ctrl = old_ctrl;
> -	if (panel->backlight.edp.intel.sdr_uses_aux) {
> +	if (intel_dp_aux_in_hdr_mode(conn_state) ||
> +	    panel->backlight.edp.intel.sdr_uses_aux) {
>  		ctrl |= INTEL_EDP_HDR_TCON_BRIGHTNESS_AUX_ENABLE;
> +
>  		intel_dp_aux_hdr_set_aux_backlight(conn_state, level);
>  	} else {
>  		u32 pwm_level = intel_backlight_level_to_pwm(connector, level);
> @@ -272,10 +348,18 @@ intel_dp_aux_hdr_enable_backlight(const struct intel_crtc_state *crtc_state,
>  		ctrl &= ~INTEL_EDP_HDR_TCON_BRIGHTNESS_AUX_ENABLE;
>  	}
>  
> +	if (intel_dp_aux_in_hdr_mode(conn_state))
> +		intel_dp_aux_fill_hdr_tcon_params(conn_state, &ctrl);
> +
>  	if (ctrl != old_ctrl &&
>  	    drm_dp_dpcd_writeb(&intel_dp->aux, INTEL_EDP_HDR_GETSET_CTRL_PARAMS, ctrl) != 1)
>  		drm_err(&i915->drm, "[CONNECTOR:%d:%s] Failed to configure DPCD brightness controls\n",
>  			connector->base.base.id, connector->base.name);
> +
> +	if (intel_dp_aux_in_hdr_mode(conn_state)) {
> +		hdr_metadata = conn_state->hdr_output_metadata->data;
> +		intel_dp_aux_write_content_luminance(connector, hdr_metadata);
> +	}
>  }
>  
>  static void
> @@ -332,7 +416,6 @@ intel_dp_aux_hdr_setup_backlight(struct intel_connector *connector, enum pipe pi
>  		    connector->base.base.id, connector->base.name,
>  		    panel->backlight.min, panel->backlight.max);
>  
> -
>  	panel->backlight.level = intel_dp_aux_hdr_get_backlight(connector, pipe);
>  	panel->backlight.enabled = panel->backlight.level != 0;
>