[PATCH 4.4 56/67] drm/amdgpu: make sure vertical front porch is at least 1

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alex Deucher <alexander.deuc...@amd.com>

commit 0126d4b9a516256f2432ca0dc78ab293a8255378 upstream.

hw doesn't like a 0 value.

Signed-off-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/gpu/drm/amd/amdgpu/atombios_encoders.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c
+++ b/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c
@@ -298,6 +298,10 @@ bool amdgpu_atombios_encoder_mode_fixup(
            && (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 (amdgpu_encoder->active_device & (ATOM_DEVICE_LCD_SUPPORT))
                amdgpu_panel_mode_fixup(encoder, adjusted_mode);