From 49d191dd5d41ca3a6b447075d50ce5f287171f71 Mon Sep 17 00:00:00 2001
From: Puthikorn Voravootivat <puthik@chromium.org>
Date: Tue, 23 May 2017 15:38:01 -0700
Subject: [PATCH] drm/i915: Drop AUX backlight enable check for backlight control
Git-commit: 49d191dd5d41ca3a6b447075d50ce5f287171f71
Patch-mainline: v4.13-rc1
References: FATE#322643 bsc#1055900

There are some panel that
(1) does not support display backlight enable via AUX
(2) support display backlight adjustment via AUX
(3) support display backlight enable via eDP BL_ENABLE pin

The current driver required that (1) must be support to enable (2).
This patch drops that requirement.

Signed-off-by: Puthikorn Voravootivat <puthik@chromium.org>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170523223805.46372-2-puthik@chromium.org
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/intel_dp_aux_backlight.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
@@ -28,6 +28,10 @@ static void set_aux_backlight_enable(str
 {
 	uint8_t reg_val = 0;
 
+	/* Early return when display use other mechanism to enable backlight. */
+	if (!(intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP))
+		return;
+
 	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_DISPLAY_CONTROL_REGISTER,
 			      &reg_val) < 0) {
 		DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
@@ -163,10 +167,8 @@ intel_dp_aux_display_control_capable(str
 	 * the panel can support backlight control over the aux channel
 	 */
 	if (intel_dp->edp_dpcd[1] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP &&
-	    (intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
 	    (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP) &&
-	    !((intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_PIN_ENABLE_CAP) ||
-	      (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP))) {
+	    !(intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP)) {
 		DRM_DEBUG_KMS("AUX Backlight Control Supported!\n");
 		return true;
 	}