drm: rcar-du: Reject modes that fail CRTC timing requirements

Commit Message

Laurent Pinchart Nov. 20, 2018, 3:36 a.m. UTC

The hardware requires the HDSR and VDSR registers to be set to 1 or
higher. This translates to a minimum combined horizontal sync and back
porch of 20 pixels and a minimum vertical back porch of 3 lines. Reject
modes that fail those requirements.

Signed-off-by: Laurent Pinchart <[e-mail]>
---
 drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 9 +++++++++
 1 file changed, 9 insertions(+)

Patch

diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
index 79021d7aa3ce..9d425894e000 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
@@ -739,6 +739,15 @@  enum drm_mode_status rcar_du_crtc_mode_valid(struct drm_crtc *crtc,
 	if (interlaced && !rcar_du_has(rcdu, RCAR_DU_FEATURE_INTERLACED))
 		return MODE_NO_INTERLACE;
 
+	/*
+	 * The hardware requires a minimum combined horizontal sync and back
+	 * porch of 20 pixels and a minimum vertical back porch of 3 lines.
+	 */
+	if (mode->htotal - mode->hsync_start < 20)
+		return MODE_HBLANK_NARROW;
+	if (mode->crtc_vtotal - mode->crtc_vsync_end < 3)
+		return MODE_VBLANK_NARROW;
+
 	return MODE_OK;
 }