drm/i915: Correctly enable backlight brightness adjustment via DPCD

intel_dp_aux_enable_backlight() assumed that the register
BACKLIGHT_BRIGHTNESS_CONTROL_MODE can only has value 01
(DP_EDP_BACKLIGHT_CONTROL_MODE_PRESET) when initialize.

This patch fixed that by handling all cases of that register.

Signed-off-by: Puthikorn Voravootivat <puthik@chromium.org>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170511230225.142870-3-puthik@chromium.org

diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
index 341bf2cb0c25cdc6d2f215468c8bdd094dc22104..870c03fc0f3aa23f0165955060d4d309f9d64e1c 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
@@ -97,15 +97,36 @@ static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
 {
        struct intel_dp *intel_dp = enc_to_intel_dp(&connector->encoder->base);
        uint8_t dpcd_buf = 0;
+       uint8_t edp_backlight_mode = 0;
 
        set_aux_backlight_enable(intel_dp, true);
 
-       if ((drm_dp_dpcd_readb(&intel_dp->aux,
-                              DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &dpcd_buf) == 1) &&
-           ((dpcd_buf & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
-            DP_EDP_BACKLIGHT_CONTROL_MODE_PRESET))
-               drm_dp_dpcd_writeb(&intel_dp->aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
-                                  (dpcd_buf | DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD));
+       if (drm_dp_dpcd_readb(&intel_dp->aux,
+                       DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &dpcd_buf) != 1) {
+               DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
+                             DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
+               return;
+       }
+
+       edp_backlight_mode = dpcd_buf & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
+
+       switch (edp_backlight_mode) {
+       case DP_EDP_BACKLIGHT_CONTROL_MODE_PWM:
+       case DP_EDP_BACKLIGHT_CONTROL_MODE_PRESET:
+       case DP_EDP_BACKLIGHT_CONTROL_MODE_PRODUCT:
+               dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
+               dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
+               if (drm_dp_dpcd_writeb(&intel_dp->aux,
+                       DP_EDP_BACKLIGHT_MODE_SET_REGISTER, dpcd_buf) < 0) {
+                       DRM_DEBUG_KMS("Failed to write aux backlight mode\n");
+               }
+               break;
+
+       /* Do nothing when it is already DPCD mode */
+       case DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD:
+       default:
+               break;
+       }
 }
 
 static void intel_dp_aux_disable_backlight(struct intel_connector *connector)