drm/radeon: disable ss on DP for DCE3.x

commit d8e24525094200601236fa64a54cf73e3d682f2e upstream.

Seems to cause problems with certain DP monitors.

Bug:
https://bugs.freedesktop.org/show_bug.cgi?id=40699

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[bwh: Backported to 3.2: s/radeon_crtc->//]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/gpu/drm/radeon/atombios_crtc.c b/drivers/gpu/drm/radeon/atombios_crtc.c
index 038570a..cd98c06 100644 (file)
--- a/drivers/gpu/drm/radeon/atombios_crtc.c
+++ b/drivers/gpu/drm/radeon/atombios_crtc.c
@@ -956,10 +956,13 @@ static void atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode
                                                ss_enabled =
                                                        radeon_atombios_get_ppll_ss_info(rdev, &ss,
                                                                                         ATOM_DP_SS_ID1);
-                               } else
+                               } else {
                                        ss_enabled =
                                                radeon_atombios_get_ppll_ss_info(rdev, &ss,
                                                                                 ATOM_DP_SS_ID1);
+                               }
+                               /* disable spread spectrum on DCE3 DP */
+                               ss_enabled = false;
                        }
                        break;
                case ATOM_ENCODER_MODE_LVDS: