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

commit 3104b8128d4d646a574ed9d5b17c7d10752cd70b upstream.

hw doesn't like a 0 value.

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

diff --git a/drivers/gpu/drm/radeon/atombios_encoders.c b/drivers/gpu/drm/radeon/atombios_encoders.c
index a1a7d07..cd8b341 100644 (file)
--- a/drivers/gpu/drm/radeon/atombios_encoders.c
+++ b/drivers/gpu/drm/radeon/atombios_encoders.c
@@ -90,6 +90,10 @@ 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 LVDS */
        if (radeon_encoder->active_device & (ATOM_DEVICE_LCD_SUPPORT))
                radeon_panel_mode_fixup(encoder, adjusted_mode);