[PATCH 4.2.y-ckt 38/59] drm/amdgpu: make sure vertical front porch is at least 1

[Kamal Mostafa]

4.2.8-ckt10 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Alex Deucher <alexander.deucher at amd.com>

commit 0126d4b9a516256f2432ca0dc78ab293a8255378 upstream.

hw doesn't like a 0 value.

Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/gpu/drm/amd/amdgpu/atombios_encoders.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c b/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c
index e605574..3ea2ad1 100644
--- 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(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 (amdgpu_encoder->active_device & (ATOM_DEVICE_LCD_SUPPORT))
 		amdgpu_panel_mode_fixup(encoder, adjusted_mode);
-- 
2.7.4