mdio_bus: Issue GPIO RESET to PHYs.

Some boards [1] leave the PHYs at an invalid state
during system power-up or reset thus causing unreliability
issues with the PHY which manifests as PHY not being detected
or link not functional. To fix this, these PHYs need to be RESET
via a GPIO connected to the PHY's RESET pin.

Some boards have a single GPIO controlling the PHY RESET pin of all
PHYs on the bus whereas some others have separate GPIOs controlling
individual PHY RESETs.

In both cases, the RESET de-assertion cannot be done in the PHY driver
as the PHY will not probe till its reset is de-asserted.
So do the RESET de-assertion in the MDIO bus driver.

[1] - am572x-idk, am571x-idk, a437x-idk

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/Documentation/devicetree/bindings/net/mdio.txt b/Documentation/devicetree/bindings/net/mdio.txt
new file mode 100644 (file)
index 0000000..4ffbbac
--- /dev/null
+++ b/Documentation/devicetree/bindings/net/mdio.txt
@@ -0,0 +1,33 @@
+Common MDIO bus properties.
+
+These are generic properties that can apply to any MDIO bus.
+
+Optional properties:
+- reset-gpios: List of one or more GPIOs that control the RESET lines
+  of the PHYs on that MDIO bus.
+- reset-delay-us: RESET pulse width in microseconds as per PHY datasheet.
+
+A list of child nodes, one per device on the bus is expected. These
+should follow the generic phy.txt, or a device specific binding document.
+
+Example :
+This example shows these optional properties, plus other properties
+required for the TI Davinci MDIO driver.
+
+       davinci_mdio: ethernet@0x5c030000 {
+               compatible = "ti,davinci_mdio";
+               reg = <0x5c030000 0x1000>;
+               #address-cells = <1>;
+               #size-cells = <0>;
+
+               reset-gpios = <&gpio2 5 GPIO_ACTIVE_LOW>;
+               reset-delay-us = <2>;   /* PHY datasheet states 1us min */
+
+               ethphy0: ethernet-phy@1 {
+                       reg = <1>;
+               };
+
+               ethphy1: ethernet-phy@3 {
+                       reg = <3>;
+               };
+       };

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 5a214f3..a898e5c 100644 (file)
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -22,8 +22,11 @@
 #include <linux/init.h>
 #include <linux/delay.h>
 #include <linux/device.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
 #include <linux/of_device.h>
 #include <linux/of_mdio.h>
+#include <linux/of_gpio.h>
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/skbuff.h>
@@ -337,6 +340,7 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
 {
        struct mdio_device *mdiodev;
        int i, err;
+       struct gpio_desc *gpiod;
 
        if (NULL == bus || NULL == bus->name ||
            NULL == bus->read || NULL == bus->write)
@@ -363,6 +367,35 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
        if (bus->reset)
                bus->reset(bus);
 
+       /* de-assert bus level PHY GPIO resets */
+       if (bus->num_reset_gpios > 0) {
+               bus->reset_gpiod = devm_kcalloc(&bus->dev,
+                                                bus->num_reset_gpios,
+                                                sizeof(struct gpio_desc *),
+                                                GFP_KERNEL);
+               if (!bus->reset_gpiod)
+                       return -ENOMEM;
+       }
+
+       for (i = 0; i < bus->num_reset_gpios; i++) {
+               gpiod = devm_gpiod_get_index(&bus->dev, "reset", i,
+                                            GPIOD_OUT_LOW);
+               if (IS_ERR(gpiod)) {
+                       err = PTR_ERR(gpiod);
+                       if (err != -ENOENT) {
+                               dev_err(&bus->dev,
+                                       "mii_bus %s couldn't get reset GPIO\n",
+                                       bus->id);
+                               return err;
+                       }
+               } else {
+                       bus->reset_gpiod[i] = gpiod;
+                       gpiod_set_value_cansleep(gpiod, 1);
+                       udelay(bus->reset_delay_us);
+                       gpiod_set_value_cansleep(gpiod, 0);
+               }
+       }
+
        for (i = 0; i < PHY_MAX_ADDR; i++) {
                if ((bus->phy_mask & (1 << i)) == 0) {
                        struct phy_device *phydev;
@@ -390,6 +423,13 @@ error:
                mdiodev->device_remove(mdiodev);
                mdiodev->device_free(mdiodev);
        }
+
+       /* Put PHYs in RESET to save power */
+       for (i = 0; i < bus->num_reset_gpios; i++) {
+               if (bus->reset_gpiod[i])
+                       gpiod_set_value_cansleep(bus->reset_gpiod[i], 1);
+       }
+
        device_del(&bus->dev);
        return err;
 }
@@ -411,6 +451,13 @@ void mdiobus_unregister(struct mii_bus *bus)
                mdiodev->device_remove(mdiodev);
                mdiodev->device_free(mdiodev);
        }
+
+       /* Put PHYs in RESET to save power */
+       for (i = 0; i < bus->num_reset_gpios; i++) {
+               if (bus->reset_gpiod[i])
+                       gpiod_set_value_cansleep(bus->reset_gpiod[i], 1);
+       }
+
        device_del(&bus->dev);
 }
 EXPORT_SYMBOL(mdiobus_unregister);

diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
index 0b29798..7e4c80f 100644 (file)
--- a/drivers/of/of_mdio.c
+++ b/drivers/of/of_mdio.c
@@ -22,6 +22,8 @@
 #include <linux/of_net.h>
 #include <linux/module.h>
 
+#define DEFAULT_GPIO_RESET_DELAY       10      /* in microseconds */
+
 MODULE_AUTHOR("Grant Likely <grant.likely@secretlab.ca>");
 MODULE_LICENSE("GPL");
 
@@ -221,6 +223,11 @@ int of_mdiobus_register(struct mii_bus *mdio, struct device_node *np)
 
        mdio->dev.of_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->num_reset_gpios = of_gpio_named_count(np, "reset-gpios");
+
        /* Register the MDIO bus */
        rc = mdiobus_register(mdio);
        if (rc)

diff --git a/include/linux/phy.h b/include/linux/phy.h
index 624cecf..37ca77d 100644 (file)
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -217,6 +217,13 @@ struct mii_bus {
         * matching its address
         */
        int irq[PHY_MAX_ADDR];
+
+       /* GPIO reset pulse width in microseconds */
+       int reset_delay_us;
+       /* Number of reset GPIOs */
+       int num_reset_gpios;
+       /* Array of RESET GPIO descriptors */
+       struct gpio_desc **reset_gpiod;
 };
 #define to_mii_bus(d) container_of(d, struct mii_bus, dev)