[PATCH net v4 02/15] net: stmmac: reuse the MDIO reset GPIO on resume

[James Hilliard <james.hilliard1@gmail.com>]

MDIO bus registration acquires the optional snps,reset GPIO through
devres. A later bus reset must reuse that descriptor: requesting the
same exclusive GPIO again returns -EBUSY while devres still owns it.
Cache the successfully acquired descriptor for subsequent resets.
Propagate acquisition errors without caching an error pointer.

Fixes: 7c86f20d15b7 ("net: stmmac: use GPIO descriptors in stmmac_mdio_reset")
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac.h      |  1 +
 drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c | 18 ++++++++++++------
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index 7582fca63741..c7c876408d85 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -287,6 +287,7 @@ struct stmmac_priv {
 
 	unsigned int pause_time;
 	struct mii_bus *mii;
+	struct gpio_desc *mdio_reset_gpio;
 
 	struct stmmac_pcs *integrated_pcs;
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
index afe98ff5bdcb..07d5eab05996 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
@@ -386,14 +386,20 @@ int stmmac_mdio_reset(struct mii_bus *bus)
 
 #ifdef CONFIG_OF
 	if (priv->device->of_node) {
-		struct gpio_desc *reset_gpio;
+		struct gpio_desc *reset_gpio = priv->mdio_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);
+		/* The bus reset also runs on resume. Devres retains the GPIO
+		 * until unbind, so do not request an already owned line again.
+		 */
+		if (!reset_gpio) {
+			reset_gpio = devm_gpiod_get_optional(priv->device,
+							     "snps,reset",
+							     GPIOD_OUT_LOW);
+			if (IS_ERR(reset_gpio))
+				return PTR_ERR(reset_gpio);
+			priv->mdio_reset_gpio = reset_gpio;
+		}
 
 		device_property_read_u32_array(priv->device,
 					       "snps,reset-delays-us",

-- 
2.53.0