drm: rcar-du: lvds: Set LVEN and LVRES bits together on D3

[ Upstream commit 00d082cc ]

On the D3 SoC the LVDS PHY must be enabled in the same register write
that enables the LVDS output. Skip writing the LVEN bit independently
on that platform, it will be set by the write that sets LVRES.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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

@@ -485,9 +485,13 @@ static void rcar_lvds_enable(struct drm_bridge *bridge)
 	}
 
 	if (lvds->info->quirks & RCAR_LVDS_QUIRK_GEN3_LVEN) {
-		/* Turn on the LVDS PHY. */
+		/*
+		 * Turn on the LVDS PHY. On D3, the LVEN and LVRES bit must be
+		 * set at the same time, so don't write the register yet.
+		 */
 		lvdcr0 |= LVDCR0_LVEN;
-		rcar_lvds_write(lvds, LVDCR0, lvdcr0);
+		if (!(lvds->info->quirks & RCAR_LVDS_QUIRK_PWD))
+			rcar_lvds_write(lvds, LVDCR0, lvdcr0);
 	}
 
 	if (!(lvds->info->quirks & RCAR_LVDS_QUIRK_EXT_PLL)) {