drm: rcar-du: lvds: Fix LVDS startup on R-Car Gen2

[ Upstream commit 8525d04b ]

According to the latest revision 2.00 of the R-Car Gen2 manual, the LVDS
and the bias circuit must be enabled after the LVDS I/O pins are
enabled, not before. Fix the Gen2 LVDS startup sequence accordingly.

While at it, also fix the comment preceding the first LVDCR0 write that
still talks about hardcoding the LVDS mode 0.

Fixes: 90374b5c ("drm/rcar-du: Add internal LVDS encoder support")
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Tested-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/rcar-du/rcar_du_lvdsenc.c

@@ -59,11 +59,8 @@ static void rcar_du_lvdsenc_start_gen2(struct rcar_du_lvdsenc *lvds,
 
 	rcar_lvds_write(lvds, LVDPLLCR, pllcr);
 
-	/*
-	 * Select the input, hardcode mode 0, enable LVDS operation and turn
-	 * bias circuitry on.
-	 */
-	lvdcr0 = (lvds->mode << LVDCR0_LVMD_SHIFT) | LVDCR0_BEN | LVDCR0_LVEN;
+	/* Select the input and set the LVDS mode. */
+	lvdcr0 = lvds->mode << LVDCR0_LVMD_SHIFT;
 	if (rcrtc->index == 2)
 		lvdcr0 |= LVDCR0_DUSEL;
 	rcar_lvds_write(lvds, LVDCR0, lvdcr0);
@@ -74,6 +71,10 @@ static void rcar_du_lvdsenc_start_gen2(struct rcar_du_lvdsenc *lvds,
 			LVDCR1_CHSTBY_GEN2(1) | LVDCR1_CHSTBY_GEN2(0) |
 			LVDCR1_CLKSTBY_GEN2);
 
+	/* Enable LVDS operation and turn bias circuitry on. */
+	lvdcr0 |= LVDCR0_BEN | LVDCR0_LVEN;
+	rcar_lvds_write(lvds, LVDCR0, lvdcr0);
+
 	/*
 	 * Turn the PLL on, wait for the startup delay, and turn the output
 	 * on.