drm/i915/bios: set default backlight controller index

With backlight controller set to -1 in intel_panel_init_alloc() to
distinguish uninitialized values, and controller later being set only if
it's present in VBT, we can end up with -1 for the controller:

    [drm:intel_bios_init_panel [i915]] VBT backlight PWM modulation
    frequency 200 Hz, active high, min brightness 0, level 255,
    controller 4294967295

There's no harm if it happens on platforms that ignore controller due to
only one backlight controller being present, like on VLV above, but play
it safe.

Fixes: bf38bba3e7d6 ("drm/i915: Try to use the correct power sequencer intiially on bxt/glk")
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230207111626.1839645-1-jani.nikula@intel.com
(cherry picked from commit a0dcb06d29d9e477e1984dc3859e61568361fc1a)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
index 1cd8af88ce503e3c9fe98f655da39e088f3df10c..04b846440de68e1e7bc7ed7d03d9b653562dfdf5 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_bios.c
+++ b/drivers/gpu/drm/i915/display/intel_bios.c
@@ -1033,6 +1033,7 @@ parse_lfp_backlight(struct drm_i915_private *i915,
        }
 
        panel->vbt.backlight.type = INTEL_BACKLIGHT_DISPLAY_DDI;
+       panel->vbt.backlight.controller = 0;
        if (i915->display.vbt.version >= 191) {
                size_t exp_size;