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

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

On Thu, Mar 07, 2024 at 05:27:31AM +0000, Kandpal, Suraj wrote:
> 
> 
> > -----Original Message-----
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Sent: Wednesday, March 6, 2024 5:57 PM
> > To: Kandpal, Suraj <suraj.kandpal@intel.com>
> > Cc: intel-gfx@lists.freedesktop.org; Shankar, Uma <uma.shankar@intel.com>;
> > Nautiyal, Ankit K <ankit.k.nautiyal@intel.com>
> > Subject: Re: [PATCH] drm/i915/dp: Enable AUX based backlight for HDR
> > 
> > On Wed, Mar 06, 2024 at 02:29:15PM +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]
> > >
> > > Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
> > > ---
> > >  .../drm/i915/display/intel_dp_aux_backlight.c | 30
> > > ++++++++++++++-----
> > >  1 file changed, 22 insertions(+), 8 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 4f58efdc688a..1b6f14dacf3b 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.
> > > @@ -221,7 +216,7 @@ intel_dp_aux_hdr_set_backlight(const struct
> > drm_connector_state *conn_state, u32
> > >  	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 (panel->backlight.edp.intel.sdr_uses_aux ||
> > > +conn_state->hdr_output_metadata) {
> > >  		intel_dp_aux_hdr_set_aux_backlight(conn_state, level);
> > >  	} else {
> > >  		const u32 pwm_level =
> > intel_backlight_level_to_pwm(connector,
> > > level); @@ -251,8 +246,15 @@ 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 (panel->backlight.edp.intel.sdr_uses_aux ||
> > > +conn_state->hdr_output_metadata) {
> > >  		ctrl |= INTEL_EDP_HDR_TCON_BRIGHTNESS_AUX_ENABLE;
> > > +
> > > +		if (conn_state->hdr_output_metadata) {
> > > +			ctrl |=
> > INTEL_EDP_HDR_TCON_SEGMENTED_BACKLIGHT_ENABLE;
> > > +			ctrl |=
> > INTEL_EDP_HDR_TCON_2084_DECODE_ENABLE;
> > > +			ctrl |=
> > INTEL_EDP_HDR_TCON_2020_GAMUT_ENABLE;
> > > +		}
> > 
> > Wasn't bunch of this stuff supposed to be only used with older hw, and more
> > recent panels were supposed to pick this up more or less automagically from
> > the HDR metadata?
> > 
> > I seem to also recall that there are a bunch of capability bits we should
> > probably be checking somewhere...
> > 
> 
> Hi Ville,
> Thanks for the review
> You are correct I had a look into it, content luminance will will fill from the static metadata from ICL onwards will get that corrected 
> As for capability check that was already being done in the function intel_dp_aux_supports_hdr_backlight()

I meant the HDR TCON caps. I don't see us checking any of that
currently.

> I soon send a revision with the fixes.
> 
> Regards,
> Suraj Kandpal
> > > +
> > >  		intel_dp_aux_hdr_set_aux_backlight(conn_state, level);
> > >  	} else {
> > >  		u32 pwm_level = intel_backlight_level_to_pwm(connector,
> > level); @@
> > > -292,9 +294,11 @@ intel_dp_aux_hdr_setup_backlight(struct
> > > intel_connector *connector, enum pipe pi  {
> > >  	struct drm_i915_private *i915 = to_i915(connector->base.dev);
> > >  	struct intel_panel *panel = &connector->panel;
> > > +	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
> > >  	struct drm_luminance_range_info *luminance_range =
> > >  		&connector->base.display_info.luminance_range;
> > >  	int ret;
> > > +	u8 buf[4];
> > >
> > >  	drm_dbg_kms(&i915->drm, "[CONNECTOR:%d:%s] SDR backlight is
> > controlled through %s\n",
> > >  		    connector->base.base.id, connector->base.name, @@ -
> > 318,11
> > > +322,21 @@ intel_dp_aux_hdr_setup_backlight(struct intel_connector
> > *connector, enum pipe pi
> > >  		panel->backlight.min = 0;
> > >  	}
> > >
> > > +	buf[0] = connector->base.hdr_sink_metadata.hdmi_type1.max_cll &
> > 0xFF;
> > > +	buf[1] = (connector->base.hdr_sink_metadata.hdmi_type1.max_cll &
> > 0xFF00) >> 8;
> > > +	buf[2] = connector->base.hdr_sink_metadata.hdmi_type1.max_fall &
> > 0xFF;
> > > +	buf[3] = (connector->base.hdr_sink_metadata.hdmi_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,
> > > +			    "Not able to write content luminence to DPCD
> > register
> > > +err:-%d\n", ret);
> > > +
> > >  	drm_dbg_kms(&i915->drm, "[CONNECTOR:%d:%s] Using AUX HDR
> > interface for backlight control (range %d..%d)\n",
> > >  		    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;
> > >
> > > --
> > > 2.43.2
> > 
> > --
> > Ville Syrjälä
> > Intel

-- 
Ville Syrjälä
Intel