drm/radeon: make sure vertical front porch is at least 1

hw doesn't like a 0 value.

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

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/atombios_encoders.c b/drivers/gpu/drm/radeon/atombios_encoders.c
index edd05cdb0cd8..587cae4e73c9 100644
--- a/drivers/gpu/drm/radeon/atombios_encoders.c
+++ b/drivers/gpu/drm/radeon/atombios_encoders.c
@@ -310,6 +310,10 @@ static bool radeon_atom_mode_fixup(struct drm_encoder *encoder,
             && (mode->crtc_vsync_start < (mode->crtc_vdisplay + 2)))
                 adjusted_mode->crtc_vsync_start = adjusted_mode->crtc_vdisplay + 2;
 
+        /* vertical FP must be at least 1 */
+        if (mode->crtc_vsync_start == mode->crtc_vdisplay)
+                adjusted_mode->crtc_vsync_start++;
+
         /* get the native mode for scaling */
         if (radeon_encoder->active_device & (ATOM_DEVICE_LCD_SUPPORT)) {
                 radeon_panel_mode_fixup(encoder, adjusted_mode);