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

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

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...

> +
>  		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