[Intel-gfx] [PATCH v3] drm/i915: Check backlight type while doing eDP backlight initializaiton

[Lee Shawn C]

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 at linux.intel.com>
Cc: Jani Nikula <jani.nikula at intel.com>
Cc: Jose Roberto de Souza <jose.souza at intel.com>
Cc: Cooper Chiou <cooper.chiou at intel.com>

Signed-off-by: Lee Shawn C <shawn.c.lee at intel.com>
---
 drivers/gpu/drm/i915/display/intel_bios.h             | 1 +
 drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 5 ++++-
 drivers/gpu/drm/i915/i915_params.c                    | 5 +++--
 drivers/gpu/drm/i915/i915_params.h                    | 2 +-
 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;
-- 
2.7.4