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 <laurent.pinchart+rene...@ideasonboard.com>
---
drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 9 +++++++++
1 file changed, 9 insertions(+)
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;
}
--
Regards,
Laurent Pinchart
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