From: Maxime Ripard <maxime.ripard@free-electrons.com>
Date: Wed, 10 Jan 2018 16:59:41 +0100
Subject: drm/panel: lvds: Handle the optional regulator case properly
Git-commit: a0d605372a279d71abd29ed985b9a51e66e12170
Patch-mainline: v4.16-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

The devm_regulator_get_optional function, unlike it was assumed in the
commit a1c55bccf600 ("drm/panel: lvds: Add support for the power-supply
property"), is actually returning an error pointer with -ENODEV instead of
NULL when there's no regulator to find.

Make sure we handle that case properly.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Fixes: a1c55bccf600 ("drm/panel: lvds: Add support for the power-supply property")
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180110155941.16109-1-maxime.ripard@free-electrons.com

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/panel/panel-lvds.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/panel/panel-lvds.c
+++ b/drivers/gpu/drm/panel/panel-lvds.c
@@ -215,8 +215,15 @@ static int panel_lvds_probe(struct platf
 	lvds->supply = devm_regulator_get_optional(lvds->dev, "power");
 	if (IS_ERR(lvds->supply)) {
 		ret = PTR_ERR(lvds->supply);
-		dev_err(lvds->dev, "failed to request regulator: %d\n", ret);
-		return ret;
+
+		if (ret != -ENODEV) {
+			if (ret != -EPROBE_DEFER)
+				dev_err(lvds->dev, "failed to request regulator: %d\n",
+					ret);
+			return ret;
+		}
+
+		lvds->supply = NULL;
 	}
 
 	/* Get GPIOs and backlight controller. */