drm/radeon/atom: fix dithering on certain panels

We need to specify the encoder mode as LVDS for eDP
when using the Crtc_Source atom table in order to properly
set up the FMT hardware.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=73911

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

diff --git a/drivers/gpu/drm/radeon/atombios_encoders.c b/drivers/gpu/drm/radeon/atombios_encoders.c
index e6eb5097597f6088dde34638ee9b94cca5bc8950..2b2908440644e8908accbeabc855d5c5066c7d47 100644 (file)
--- a/drivers/gpu/drm/radeon/atombios_encoders.c
+++ b/drivers/gpu/drm/radeon/atombios_encoders.c
@@ -1884,8 +1884,11 @@ atombios_set_encoder_crtc_source(struct drm_encoder *encoder)
                                        args.v2.ucEncodeMode = ATOM_ENCODER_MODE_CRT;
                                else
                                        args.v2.ucEncodeMode = atombios_get_encoder_mode(encoder);
-                       } else
+                       } else if (radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT)) {
+                               args.v2.ucEncodeMode = ATOM_ENCODER_MODE_LVDS;
+                       } else {
                                args.v2.ucEncodeMode = atombios_get_encoder_mode(encoder);
+                       }
                        switch (radeon_encoder->encoder_id) {
                        case ENCODER_OBJECT_ID_INTERNAL_UNIPHY:
                        case ENCODER_OBJECT_ID_INTERNAL_UNIPHY1: