[PATCH v3] net: stmmac: avoid repeated devm_gpiod_get_optional in mdio

[Liu Xiang <liu.xiang@zlingsmart.com>]

During system resume, stmmac_resume() calls stmmac_mdio_reset().
This results in repeated calls to devm_gpiod_get_optional() for the same
GPIO. The second invocation returns an error since the GPIO descriptor has
already been obtained.

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Liu Xiang <liu.xiang@zlingsmart.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac.h  |  2 +
 .../net/ethernet/stmicro/stmmac/stmmac_mdio.c | 43 +++++++++++--------
 2 files changed, 26 insertions(+), 19 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index 33667a267..34ebc6f3a 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -372,6 +372,8 @@ struct stmmac_priv {
 	struct bpf_prog *xdp_prog;
 
 	struct devlink *devlink;
+
+	struct gpio_desc *reset_gpio;
 };
 
 enum stmmac_state {
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
index a7c2496b3..c0b35b8e2 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
@@ -386,29 +386,26 @@ int stmmac_mdio_reset(struct mii_bus *bus)
 
 #ifdef CONFIG_OF
 	if (priv->device->of_node) {
-		struct gpio_desc *reset_gpio;
-		u32 delays[3] = { 0, 0, 0 };
+		if (priv->reset_gpio) {
+			u32 delays[3] = { 0, 0, 0 };
 
-		reset_gpio = devm_gpiod_get_optional(priv->device,
-						     "snps,reset",
-						     GPIOD_OUT_LOW);
-		if (IS_ERR(reset_gpio))
-			return PTR_ERR(reset_gpio);
+			device_property_read_u32_array(priv->device,
+						       "snps,reset-delays-us",
+						       delays,
+						       ARRAY_SIZE(delays));
 
-		device_property_read_u32_array(priv->device,
-					       "snps,reset-delays-us",
-					       delays, ARRAY_SIZE(delays));
+			gpiod_set_value_cansleep(priv->reset_gpio, 0);
+			if (delays[0])
+				msleep(DIV_ROUND_UP(delays[0], 1000));
 
-		if (delays[0])
-			msleep(DIV_ROUND_UP(delays[0], 1000));
+			gpiod_set_value_cansleep(priv->reset_gpio, 1);
+			if (delays[1])
+				msleep(DIV_ROUND_UP(delays[1], 1000));
 
-		gpiod_set_value_cansleep(reset_gpio, 1);
-		if (delays[1])
-			msleep(DIV_ROUND_UP(delays[1], 1000));
-
-		gpiod_set_value_cansleep(reset_gpio, 0);
-		if (delays[2])
-			msleep(DIV_ROUND_UP(delays[2], 1000));
+			gpiod_set_value_cansleep(priv->reset_gpio, 0);
+			if (delays[2])
+				msleep(DIV_ROUND_UP(delays[2], 1000));
+		}
 	}
 #endif
 
@@ -648,6 +645,14 @@ int stmmac_mdio_register(struct net_device *ndev)
 	if (priv->plat->core_type == DWMAC_CORE_XGMAC)
 		stmmac_xgmac2_mdio_read_c45(new_bus, 0, 0, 0);
 
+	priv->reset_gpio = devm_gpiod_get_optional(priv->device,
+						   "snps,reset",
+						    GPIOD_ASIS);
+	if (IS_ERR(priv->reset_gpio)) {
+		priv->reset_gpio = NULL;
+		dev_warn(dev, "No reset GPIO found\n");
+	}
+
 	/* If fixed-link is set, skip PHY scanning */
 	fwnode = priv->plat->port_node;
 	if (!fwnode)
-- 
2.34.1