drm/rockchip: vop2: Check writeback fifo depth

The fifo depth of RK356X/RK3588 writeback is 1920x4/16.
A fifo_throd larger than this value will cause a empty(zero)
writeback.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Change-Id: Id67209f7b162608dcba191ab23cf6eec11e3fc08

drivers/gpu/drm/rockchip/rockchip_drm_vop.h

@@ -852,6 +852,7 @@ struct vop2_wb_data {
 	const uint32_t *formats;
 	struct vop_rect max_output;
 	const struct vop2_wb_regs *regs;
+	uint32_t fifo_depth;
 };
 
 struct vop2_video_port_data {

drivers/gpu/drm/rockchip/rockchip_drm_vop2.c

@@ -2730,6 +2730,8 @@ static void vop2_wb_commit(struct drm_crtc *crtc)
 		spin_unlock_irqrestore(&wb->job_lock, flags);
 
 		fifo_throd = fb->pitches[0] >> 4;
+		if (fifo_throd >= vop2->data->wb->fifo_depth)
+			fifo_throd = vop2->data->wb->fifo_depth;
 		r2y = is_yuv_support(fb->format->format) && (!is_yuv_output(vcstate->bus_format));
 
 		/*

drivers/gpu/drm/rockchip/rockchip_vop2_reg.c

@@ -650,6 +650,7 @@ static const struct vop2_wb_data rk3568_vop_wb_data = {
 	.formats = formats_wb,
 	.nformats = ARRAY_SIZE(formats_wb),
 	.max_output = { 1920, 1080 },
+	.fifo_depth =  1920 * 4 / 16,
 	.regs = &rk3568_vop_wb_regs,
 };