drm/i915: Check backlight type while doing eDP backlight initializaiton

If LFP backlight type setting from VBT was "VESA eDP AUX Interface".
Driver should check panel capability and try to initialize aux backlight.
No matter i915_modparams.enable_dpcd_backlight was enabled or not.

v2: access dev_priv->vbt.backlight.type directly and remove unused function.
v3: 1. Modify i915.enable_dpcd_backlight type from bool to int and give default
       value as 0 (disable).
    2. Add a judgement to check LFP backlight type was aux interface or not.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Jose Roberto de Souza <jose.souza@intel.com>
Cc: Cooper Chiou <cooper.chiou@intel.com>

Signed-off-by: Lee Shawn C <shawn.c.lee@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1561045456-12171-1-git-send-email-shawn.c.lee@intel.com

4 files changed, 9 insertions, 4 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_bios.h b/drivers/gpu/drm/i915/display/intel_bios.h
index 4e42cfaf61a7..0b7be6389a07 100644
--- a/drivers/gpu/drm/i915/display/intel_bios.h
+++ b/drivers/gpu/drm/i915/display/intel_bios.h
@@ -42,6 +42,7 @@ enum intel_backlight_type {
 	INTEL_BACKLIGHT_DISPLAY_DDI,
 	INTEL_BACKLIGHT_DSI_DCS,
 	INTEL_BACKLIGHT_PANEL_DRIVER_INTERFACE,
+	INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE,
 };
 
 struct edp_power_seq {
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 7ded95a334db..6b0b73479fb8 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -264,8 +264,11 @@ intel_dp_aux_display_control_capable(struct intel_connector *connector)
 int intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
 {
 	struct intel_panel *panel = &intel_connector->panel;
+	struct drm_i915_private *dev_priv = to_i915(intel_connector->base.dev);
 
-	if (!i915_modparams.enable_dpcd_backlight)
+	if (i915_modparams.enable_dpcd_backlight == 0 ||
+	    (i915_modparams.enable_dpcd_backlight == -1 &&
+	    dev_priv->vbt.backlight.type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE))
 		return -ENODEV;
 
 	if (!intel_dp_aux_display_control_capable(intel_connector))
diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 5b07766a1c26..296452f9efe4 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -169,8 +169,9 @@ i915_param_named_unsafe(inject_load_failure, uint, 0400,
 	"Force an error after a number of failure check points (0:disabled (default), N:force failure at the Nth failure check point)");
 #endif
 
-i915_param_named(enable_dpcd_backlight, bool, 0600,
-	"Enable support for DPCD backlight control (default:false)");
+i915_param_named(enable_dpcd_backlight, int, 0600,
+	"Enable support for DPCD backlight control"
+	"(-1=use per-VBT LFP backlight type setting, 0=disabled [default], 1=enabled)");
 
 #if IS_ENABLED(CONFIG_DRM_I915_GVT)
 i915_param_named(enable_gvt, bool, 0400,
diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index a4770ce46bd2..d29ade3b7de6 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -64,6 +64,7 @@ struct drm_printer;
 	param(int, reset, 2) \
 	param(unsigned int, inject_load_failure, 0) \
 	param(int, fastboot, -1) \
+	param(int, enable_dpcd_backlight, 0) \
 	param(char *, force_probe, CONFIG_DRM_I915_FORCE_PROBE) \
 	/* leave bools at the end to not create holes */ \
 	param(bool, alpha_support, IS_ENABLED(CONFIG_DRM_I915_ALPHA_SUPPORT)) \
@@ -76,7 +77,6 @@ struct drm_printer;
 	param(bool, verbose_state_checks, true) \
 	param(bool, nuclear_pageflip, false) \
 	param(bool, enable_dp_mst, true) \
-	param(bool, enable_dpcd_backlight, false) \
 	param(bool, enable_gvt, false)
 
 #define MEMBER(T, member, ...) T member;