drm/i915: Pick the backlight controller based on VBT on ICP+

Use the second backlight controller on ICP+ if the VBT asks
us to do so.

On pre-MTP we also check the chicken bit to make sure the
pins have been correctly muxed by the firmware.

Cc: stable@vger.kernel.org
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8016
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230207064337.18697-4-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c b/drivers/gpu/drm/i915/display/intel_backlight.c
index 5b7da72..a4e4b7f 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_backlight.c
@@ -1431,6 +1431,30 @@ bxt_setup_backlight(struct intel_connector *connector, enum pipe unused)
        return 0;
 }
 
+static int cnp_num_backlight_controllers(struct drm_i915_private *i915)
+{
+       if (INTEL_PCH_TYPE(i915) >= PCH_DG1)
+               return 1;
+
+       if (INTEL_PCH_TYPE(i915) >= PCH_ICP)
+               return 2;
+
+       return 1;
+}
+
+static bool cnp_backlight_controller_is_valid(struct drm_i915_private *i915, int controller)
+{
+       if (controller < 0 || controller >= cnp_num_backlight_controllers(i915))
+               return false;
+
+       if (controller == 1 &&
+           INTEL_PCH_TYPE(i915) >= PCH_ICP &&
+           INTEL_PCH_TYPE(i915) < PCH_MTP)
+               return intel_de_read(i915, SOUTH_CHICKEN1) & ICP_SECOND_PPS_IO_SELECT;
+
+       return true;
+}
+
 static int
 cnp_setup_backlight(struct intel_connector *connector, enum pipe unused)
 {
@@ -1440,10 +1464,14 @@ cnp_setup_backlight(struct intel_connector *connector, enum pipe unused)
 
        /*
         * CNP has the BXT implementation of backlight, but with only one
-        * controller. TODO: ICP has multiple controllers but we only use
-        * controller 0 for now.
+        * controller. ICP+ can have two controllers, depending on pin muxing.
         */
-       panel->backlight.controller = 0;
+       panel->backlight.controller = connector->panel.vbt.backlight.controller;
+       if (!cnp_backlight_controller_is_valid(i915, panel->backlight.controller)) {
+               drm_dbg_kms(&i915->drm, "Invalid backlight controller %d, assuming 0\n",
+                           panel->backlight.controller);
+               panel->backlight.controller = 0;
+       }
 
        pwm_ctl = intel_de_read(i915,
                                BXT_BLC_PWM_CTL(panel->backlight.controller));