drm/nouveau/kms/nv50-: Explicitly check DPCD backlights for aux enable/brightness

Since we don't support hybrid AUX/PWM backlights in nouveau right now,
let's add some explicit checks so that we don't break nouveau once we
enable support for these backlights in other drivers.

Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211105183342.130810-3-lyude@redhat.com

diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c
index 1cbd71a..ae2f2ab 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_backlight.c
+++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c
@@ -308,7 +308,10 @@ nv50_backlight_init(struct nouveau_backlight *bl,
                if (ret < 0)
                        return ret;
 
-               if (drm_edp_backlight_supported(edp_dpcd)) {
+               /* TODO: Add support for hybrid PWM/DPCD panels */
+               if (drm_edp_backlight_supported(edp_dpcd) &&
+                   (edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
+                   (edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP)) {
                        NV_DEBUG(drm, "DPCD backlight controls supported on %s\n",
                                 nv_conn->base.name);