[PATCH v4] net: stmmac: avoid repeated devm_gpiod_get_optional in mdio reset on resume

[PATCH v4] net: stmmac: avoid repeated devm_gpiod_get_optional in mdio reset on resume

[Liu Xiang]

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.

Fixes: 7c86f20d15b7c113 ("net: stmmac: use GPIO descriptors in stmmac_mdio_reset")
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 | 22 ++++++++++---------
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index 8ba8f03e1..afec9c3a2 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -383,6 +383,8 @@ 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 afe98ff5b..26f7d0611 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
@@ -385,28 +385,22 @@ int stmmac_mdio_reset(struct mii_bus *bus)
 	unsigned int mii_address = priv->hw->mii.addr;
 
 #ifdef CONFIG_OF
-	if (priv->device->of_node) {
-		struct gpio_desc *reset_gpio;
+	if (priv->device->of_node && 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));
 
+		gpiod_set_value_cansleep(priv->reset_gpio, 0);
 		if (delays[0])
 			msleep(DIV_ROUND_UP(delays[0], 1000));
 
-		gpiod_set_value_cansleep(reset_gpio, 1);
+		gpiod_set_value_cansleep(priv->reset_gpio, 1);
 		if (delays[1])
 			msleep(DIV_ROUND_UP(delays[1], 1000));
 
-		gpiod_set_value_cansleep(reset_gpio, 0);
+		gpiod_set_value_cansleep(priv->reset_gpio, 0);
 		if (delays[2])
 			msleep(DIV_ROUND_UP(delays[2], 1000));
 	}
@@ -666,6 +660,14 @@ 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 = dev_fwnode(priv->device);
 	if (fwnode) {
-- 
2.34.1

Re: [PATCH v4] net: stmmac: avoid repeated devm_gpiod_get_optional in mdio reset on resume

[Andrew Lunn]

On Fri, May 15, 2026 at 02:56:52PM +0800, Liu Xiang wrote:
> 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.
> 
> Fixes: 7c86f20d15b7c113 ("net: stmmac: use GPIO descriptors in stmmac_mdio_reset")
> Suggested-by: Andrew Lunn <andrew@lunn.ch>
> Signed-off-by: Liu Xiang <liu.xiang@zlingsmart.com>
> ---

Under the --- you should include the history of the patch. This is
version 4. How does it differ to v1, v2, v3.

> +	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");
> +	}

Please read the documentation for devm_gpiod_get_optional().

There are three different cases:

1) A GPIO is returned
2) No GPIO is found in DT, which since it is optional, is O.K.
3) A real error happened, which should fail the probe.

Also, see what happens when you pass NULL to any gpiod_ method.

    Andrew

---
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