net: mdiobus: add reset-post-delay-us handling

Load new "reset-post-delay-us" value from MDIO properties,
and if configured to a greater then zero delay do a
flexible sleeping delay after MDIO bus reset deassert.
This allows devices to exit reset state before start
bus communication.
Signed-off-by: Bruno Thomsen <bruno.thomsen@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/mdio_bus.c

@@ -556,6 +556,8 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
 		gpiod_set_value_cansleep(gpiod, 1);
 		fsleep(bus->reset_delay_us);
 		gpiod_set_value_cansleep(gpiod, 0);
+		if (bus->reset_post_delay_us > 0)
+			fsleep(bus->reset_post_delay_us);
 	}
 
 	if (bus->reset) {

drivers/of/of_mdio.c

@@ -268,6 +268,8 @@ int of_mdiobus_register(struct mii_bus *mdio, struct device_node *np)
 	/* Get bus level PHY reset GPIO details */
 	mdio->reset_delay_us = DEFAULT_GPIO_RESET_DELAY;
 	of_property_read_u32(np, "reset-delay-us", &mdio->reset_delay_us);
+	mdio->reset_post_delay_us = 0;
+	of_property_read_u32(np, "reset-post-delay-us", &mdio->reset_post_delay_us);
 
 	/* Register the MDIO bus */
 	rc = mdiobus_register(mdio);

include/linux/phy.h

@@ -293,6 +293,8 @@ struct mii_bus {
 
 	/* GPIO reset pulse width in microseconds */
 	int reset_delay_us;
+	/* GPIO reset deassert delay in microseconds */
+	int reset_post_delay_us;
 	/* RESET GPIO descriptor pointer */
 	struct gpio_desc *reset_gpiod;