[PATCH net-next v3] net: mdio: force deassert MDIO reset signal

[Pierluigi Passaro]

When the reset gpio is defined within the node of the device tree
describing the PHY, the reset is initialized and managed only after
calling the fwnode_mdiobus_phy_device_register function.
However, before calling it, the MDIO communication is checked by the
get_phy_device function.
When this happens and the reset GPIO was somehow previously set down,
the get_phy_device function fails, preventing the PHY detection.
These changes force the deassert of the MDIO reset signal before
checking the MDIO channel.
The PHY may require a minimum deassert time before being responsive:
use a reasonable sleep time after forcing the deassert of the MDIO
reset signal.
Once done, free the gpio descriptor to allow managing it later.

Signed-off-by: Pierluigi Passaro <pierluigi.p@xxxxxxxxxxxxx>
Signed-off-by: FrancescoFerraro <francesco.f@xxxxxxxxxxxxx>
---
 drivers/net/mdio/fwnode_mdio.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/net/mdio/fwnode_mdio.c b/drivers/net/mdio/fwnode_mdio.c
index b782c35c4ac1..eb146eecff5c 100644
--- a/drivers/net/mdio/fwnode_mdio.c
+++ b/drivers/net/mdio/fwnode_mdio.c
@@ -8,6 +8,8 @@
 
 #include <linux/acpi.h>
 #include <linux/fwnode_mdio.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
 #include <linux/of.h>
 #include <linux/phy.h>
 #include <linux/pse-pd/pse.h>
@@ -114,6 +116,7 @@ int fwnode_mdiobus_register_phy(struct mii_bus *bus,
 {
 	struct mii_timestamper *mii_ts = NULL;
 	struct pse_control *psec = NULL;
+	struct gpio_desc *reset_gpio;
 	struct phy_device *phy;
 	bool is_c45 = false;
 	u32 phy_id;
@@ -134,10 +137,33 @@ int fwnode_mdiobus_register_phy(struct mii_bus *bus,
 	if (rc >= 0)
 		is_c45 = true;
 
+	reset_gpio = fwnode_gpiod_get_index(child, "reset", 0, GPIOD_OUT_LOW, "PHY reset");
+	if (reset_gpio == ERR_PTR(-EPROBE_DEFER)) {
+		dev_dbg(&bus->dev, "reset signal for PHY@%u not ready\n", addr);
+		return -EPROBE_DEFER;
+	} else if (IS_ERR(reset_gpio)) {
+		if (reset_gpio == ERR_PTR(-ENOENT))
+			dev_dbg(&bus->dev, "reset signal for PHY@%u not defined\n", addr);
+		else
+			dev_dbg(&bus->dev, "failed to request reset for PHY@%u, error %ld\n", addr, PTR_ERR(reset_gpio));
+		reset_gpio = NULL;
+	} else {
+		int reset_deassert_delay = 0;
+
+		dev_dbg(&bus->dev, "deassert reset signal for PHY@%u\n", addr);
+		fwnode_property_read_u32(child, "reset-deassert-us",
+					 &reset_deassert_delay);
+		if (reset_deassert_delay)
+			fsleep(reset_deassert_delay);
+	}
+
 	if (is_c45 || fwnode_get_phy_id(child, &phy_id))
 		phy = get_phy_device(bus, addr, is_c45);
 	else
 		phy = phy_device_create(bus, addr, phy_id, 0, NULL);
+
+	gpiochip_free_own_desc(reset_gpio);
+
 	if (IS_ERR(phy)) {
 		rc = PTR_ERR(phy);
 		goto clean_mii_ts;
-- 
2.37.2