phylib: Add device reset delay support

Some PHYs need a minimum time after the reset gpio was asserted and/or
deasserted. To ensure we meet these timing requirements add two new
optional devicetree parameters for the phy: reset-delay-us and
reset-post-delay-us.

Signed-off-by: Richard Leitner <richard.leitner@skidata.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/phy.txt

@@ -55,6 +55,12 @@ Optional Properties:
 
 - reset-gpios: The GPIO phandle and specifier for the PHY reset signal.
 
+- reset-delay-us: Delay after the reset was asserted in microseconds.
+  If this property is missing the delay will be skipped.
+
+- reset-post-delay-us: Delay after the reset was deasserted in microseconds.
+  If this property is missing the delay will be skipped.
+
 Example:
 
 ethernet-phy@0 {
@@ -62,4 +68,8 @@ ethernet-phy@0 {
 	interrupt-parent = <&PIC>;
 	interrupts = <35 IRQ_TYPE_EDGE_RISING>;
 	reg = <0>;
+
+	reset-gpios = <&gpio1 4 GPIO_ACTIVE_LOW>;
+	reset-delay-us = <1000>;
+	reset-post-delay-us = <2000>;
 };

drivers/net/phy/mdio_device.c

@@ -24,6 +24,7 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/unistd.h>
+#include <linux/delay.h>
 
 void mdio_device_free(struct mdio_device *mdiodev)
 {
@@ -118,8 +119,16 @@ EXPORT_SYMBOL(mdio_device_remove);
 
 void mdio_device_reset(struct mdio_device *mdiodev, int value)
 {
-	if (mdiodev->reset)
+	unsigned int d;
+
+	if (!mdiodev->reset)
+		return;
+
 	gpiod_set_value(mdiodev->reset, value);
+
+	d = value ? mdiodev->reset_delay : mdiodev->reset_post_delay;
+	if (d)
+		usleep_range(d, d + max_t(unsigned int, d / 10, 100));
 }
 EXPORT_SYMBOL(mdio_device_reset);
 

drivers/of/of_mdio.c

@@ -77,6 +77,10 @@ static int of_mdiobus_register_phy(struct mii_bus *mdio,
 	if (of_property_read_bool(child, "broken-turn-around"))
 		mdio->phy_ignore_ta_mask |= 1 << addr;
 
+	of_property_read_u32(child, "reset-delay-us", &phy->mdio.reset_delay);
+	of_property_read_u32(child, "reset-post-delay-us",
+			     &phy->mdio.reset_post_delay);
+
 	/* Associate the OF node with the device structure so it
 	 * can be looked up later */
 	of_node_get(child);

include/linux/mdio.h

@@ -41,6 +41,8 @@ struct mdio_device {
 	int addr;
 	int flags;
 	struct gpio_desc *reset;
+	unsigned int reset_delay;
+	unsigned int reset_post_delay;
 };
 #define to_mdio_device(d) container_of(d, struct mdio_device, dev)