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

[Suraj Kandpal]

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.

Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
---
 .../drm/i915/display/intel_dp_aux_backlight.c | 29 ++++++++++++++-----
 1 file changed, 21 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..14144347f13f 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;
+		}
+
 		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 +322,20 @@ intel_dp_aux_hdr_setup_backlight(struct intel_connector *connector, enum pipe pi
 		panel->backlight.min = 0;
 	}
 
+	buf[0] = panel->backlight.max & 0xFF;
+	buf[1] = (panel->backlight.max & 0xFF00) >> 8;
+	buf[2] = (connector->base.hdr_sink_metadata.hdmi_type1.max_fall & 0xFF) >> 16;
+	buf[3] = (connector->base.hdr_sink_metadata.hdmi_type1.max_fall & 0xFF00) >> 24;
+
+	ret = drm_dp_dpcd_write(&intel_dp->aux, INTEL_EDP_HDR_CONTENT_LUMINANCE, buf,
+				sizeof(buf) != sizeof(buf));
+	if (ret)
+		drm_dbg_kms(&i915->drm, "Not able to write content luminence to DPCD register\n");
+
 	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