net: ethernet: stmmac: dwmac-rk: fix optional phy regulator handling

The usual devm_regulator_get() call already handles "optional"
regulators by returning a valid dummy and printing a warning
that the dummy regulator should be described properly. This
code open coded the same behaviour, but masked any errors that
are not -EPROBE_DEFER and is quite noisy.

This change effectively unmasks and propagates regulators errors
not involving -ENODEV, downgrades the error print to warning level
if no regulator is specified and captures the probe defer message
for /sys/kernel/debug/devices_deferred.

Fixes: 2e12f53663 ("net: stmmac: dwmac-rk: Use standard devicetree property for phy regulator")
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c

@@ -1586,9 +1586,6 @@ static int phy_power_on(struct rk_priv_data *bsp_priv, bool enable)
 	int ret;
 	struct device *dev = &bsp_priv->pdev->dev;
 
-	if (!ldo)
-		return 0;
-
 	if (enable) {
 		ret = regulator_enable(ldo);
 		if (ret)
@@ -1636,14 +1633,11 @@ static struct rk_priv_data *rk_gmac_setup(struct platform_device *pdev,
 		}
 	}
 
-	bsp_priv->regulator = devm_regulator_get_optional(dev, "phy");
+	bsp_priv->regulator = devm_regulator_get(dev, "phy");
 	if (IS_ERR(bsp_priv->regulator)) {
-		if (PTR_ERR(bsp_priv->regulator) == -EPROBE_DEFER) {
-			dev_err(dev, "phy regulator is not available yet, deferred probing\n");
-			return ERR_PTR(-EPROBE_DEFER);
-		}
-		dev_err(dev, "no regulator found\n");
-		bsp_priv->regulator = NULL;
+		ret = PTR_ERR(bsp_priv->regulator);
+		dev_err_probe(dev, ret, "failed to get phy regulator\n");
+		return ERR_PTR(ret);
 	}
 
 	ret = of_property_read_string(dev->of_node, "clock_in_out", &strings);