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

[Kandpal, Suraj]

> -----Original Message-----
> From: Sebastian Wick <sebastian.wick at redhat.com>
> Sent: Friday, April 5, 2024 11:50 PM
> To: Kandpal, Suraj <suraj.kandpal at intel.com>
> Cc: intel-gfx at lists.freedesktop.org; Borah, Chaitanya Kumar
> <chaitanya.kumar.borah at intel.com>; Shankar, Uma
> <uma.shankar at intel.com>; Nautiyal, Ankit K <ankit.k.nautiyal at intel.com>;
> Murthy, Arun R <arun.r.murthy at intel.com>; Syrjala, Ville
> <ville.syrjala at intel.com>; Kumar, Naveen1 <naveen1.kumar at intel.com>
> Subject: Re: [5/7] drm/i915/dp: Enable AUX based backlight for HDR
> 
> 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 at 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?
> 

I can test it to see if we do see a blank screen if so I can add this change in otherwise
Ill stick with this.

> > +}
> > +
> >  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

Content luminance DPCD register does not need to be written from gen > ICL
It would just add an unnecessary DPCD write since specs state these values are
directly to be extracted from static_metadata_header.
Yes intel_dp_has_gamut_metadata_dip check is won't alone do the work and
an extra H/w restriction check needs to be added here.

Regards,
Suraj Kandpal 

> 
> > +
> > +	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;
> >