[Intel-gfx] [PATCH 4/5] drm/i915: Use highest frequency divider for PWM

[Puthikorn Voravootivat]

TCON tend to have better brightness scaling with lower
PWM frequency. This patch set the divider to highest
value to lower the PWM frequency.

Signed-off-by: Puthikorn Voravootivat <puthik at chromium.org>
---
 drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
index 643b604be2de..32b426006a6a 100644
--- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
@@ -116,6 +116,7 @@ static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
 	uint8_t dpcd_buf = 0;
 	uint8_t new_dpcd_buf = 0;
 	uint8_t edp_backlight_mode = 0;
+	bool freq_cap = false;
 
 	set_aux_backlight_enable(intel_dp, true);
 
@@ -146,10 +147,20 @@ static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
 		intel_dp_aux_set_dynamic_backlight_percent(intel_dp, 0, 100);
 	}
 
+	/* Use highest frequency divider if supported */
+	freq_cap = intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP;
+	if (freq_cap)
+		new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
+
 	if (new_dpcd_buf != dpcd_buf) {
 		drm_dp_dpcd_writeb(&intel_dp->aux,
 			DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf);
 	}
+
+	if (freq_cap) {
+		drm_dp_dpcd_writeb(&intel_dp->aux, DP_EDP_BACKLIGHT_FREQ_SET,
+			0xff);
+	}
 }
 
 static void intel_dp_aux_disable_backlight(struct intel_connector *connector)
-- 
2.12.0.246.ga2ecc84866-goog