drm/i915/dp: fall back to 18 bpp when sink capability is unknown

[firefly-linux-kernel-4.4.55.git] / drivers / gpu / drm / i915 / intel_display.c

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 53d77b8be76a7b9fb9a1712a00311782c80eae3e..a0ddaf1dfe14d02cf406ab2f7fa7bc2edb33e87c 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11930,11 +11930,21 @@ connected_sink_compute_bpp(struct intel_connector *connector,
                pipe_config->pipe_bpp = connector->base.display_info.bpc*3;
        }
 
-       /* Clamp bpp to 8 on screens without EDID 1.4 */
-       if (connector->base.display_info.bpc == 0 && bpp > 24) {
-               DRM_DEBUG_KMS("clamping display bpp (was %d) to default limit of 24\n",
-                             bpp);
-               pipe_config->pipe_bpp = 24;
+       /* Clamp bpp to default limit on screens without EDID 1.4 */
+       if (connector->base.display_info.bpc == 0) {
+               int type = connector->base.connector_type;
+               int clamp_bpp = 24;
+
+               /* Fall back to 18 bpp when DP sink capability is unknown. */
+               if (type == DRM_MODE_CONNECTOR_DisplayPort ||
+                   type == DRM_MODE_CONNECTOR_eDP)
+                       clamp_bpp = 18;
+
+               if (bpp > clamp_bpp) {
+                       DRM_DEBUG_KMS("clamping display bpp (was %d) to default limit of %d\n",
+                                     bpp, clamp_bpp);
+                       pipe_config->pipe_bpp = clamp_bpp;
+               }
        }
 }