drm: mxsfb: Wrap FIFO reset and comments into mxsfb_reset_block()

Wrap FIFO reset and comments into mxsfb_reset_block(), this is a clean up.
No functional change.

Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexander Stein <alexander.stein@ew.tq-group.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Robby Cai <robby.cai@nxp.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Stefan Agner <stefan@agner.ch>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220417020800.336675-1-marex@denx.de

drivers/gpu/drm/mxsfb/mxsfb_kms.c

@@ -191,6 +191,12 @@ static int mxsfb_reset_block(struct mxsfb_drm_private *mxsfb)
 {
 	int ret;
 
+	/*
+	 * It seems, you can't re-program the controller if it is still
+	 * running. This may lead to shifted pictures (FIFO issue?), so
+	 * first stop the controller and drain its FIFOs.
+	 */
+
 	ret = clear_poll_bit(mxsfb->base + LCDC_CTRL, CTRL_SFTRST);
 	if (ret)
 		return ret;
@@ -201,7 +207,20 @@ static int mxsfb_reset_block(struct mxsfb_drm_private *mxsfb)
 	if (ret)
 		return ret;
 
-	return clear_poll_bit(mxsfb->base + LCDC_CTRL, CTRL_CLKGATE);
+	ret = clear_poll_bit(mxsfb->base + LCDC_CTRL, CTRL_CLKGATE);
+	if (ret)
+		return ret;
+
+	/* Clear the FIFOs */
+	writel(CTRL1_FIFO_CLEAR, mxsfb->base + LCDC_CTRL1 + REG_SET);
+	readl(mxsfb->base + LCDC_CTRL1);
+	writel(CTRL1_FIFO_CLEAR, mxsfb->base + LCDC_CTRL1 + REG_CLR);
+	readl(mxsfb->base + LCDC_CTRL1);
+
+	if (mxsfb->devdata->has_overlay)
+		writel(0, mxsfb->base + LCDC_AS_CTRL);
+
+	return 0;
 }
 
 static dma_addr_t mxsfb_get_fb_paddr(struct drm_plane *plane)
@@ -228,26 +247,11 @@ static void mxsfb_crtc_mode_set_nofb(struct mxsfb_drm_private *mxsfb,
 	u32 vdctrl0, vsync_pulse_len, hsync_pulse_len;
 	int err;
 
-	/*
-	 * It seems, you can't re-program the controller if it is still
-	 * running. This may lead to shifted pictures (FIFO issue?), so
-	 * first stop the controller and drain its FIFOs.
-	 */
-
 	/* Mandatory eLCDIF reset as per the Reference Manual */
 	err = mxsfb_reset_block(mxsfb);
 	if (err)
 		return;
 
-	/* Clear the FIFOs */
-	writel(CTRL1_FIFO_CLEAR, mxsfb->base + LCDC_CTRL1 + REG_SET);
-	readl(mxsfb->base + LCDC_CTRL1);
-	writel(CTRL1_FIFO_CLEAR, mxsfb->base + LCDC_CTRL1 + REG_CLR);
-	readl(mxsfb->base + LCDC_CTRL1);
-
-	if (mxsfb->devdata->has_overlay)
-		writel(0, mxsfb->base + LCDC_AS_CTRL);
-
 	mxsfb_set_formats(mxsfb, bus_format);
 
 	clk_set_rate(mxsfb->clk, m->crtc_clock * 1000);