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+renesas@xxxxxxxxxxxxxxxx> --- 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
