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    Subject[PATCH v3 net-next] mdio_bus: Issue GPIO RESET to PHYs.
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    Date
    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>
    ---
    v3:
    - added more information in the DT binding document.

    v2:
    - add device tree binding document (mdio.txt)
    - specify default reset delay in of_mdio.c instead of mdio_bus.c

    Documentation/devicetree/bindings/net/mdio.txt | 33 ++++++++++++++++++++++++++
    drivers/net/phy/mdio_bus.c | 22 +++++++++++++++++
    drivers/of/of_mdio.c | 7 ++++++
    include/linux/phy.h | 5 ++++
    4 files changed, 67 insertions(+)
    create mode 100644 Documentation/devicetree/bindings/net/mdio.txt

    diff --git a/Documentation/devicetree/bindings/net/mdio.txt b/Documentation/devicetree/bindings/net/mdio.txt
    new file mode 100644
    index 0000000..3517369
    --- /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 fa7d51f..b353d99 100644
    --- 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>
    @@ -307,6 +310,7 @@ 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)
    @@ -333,6 +337,24 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
    if (bus->reset)
    bus->reset(bus);

    + /* de-assert bus level PHY GPIO resets */
    + 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) {
    + pr_err("mii_bus %s couldn't get reset GPIO\n",
    + bus->id);
    + return err;
    + }
    + } else {
    + 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;
    diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
    index 0b29798..7e4c80f 100644
    --- 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 43a7748..80a6574 100644
    --- a/include/linux/phy.h
    +++ b/include/linux/phy.h
    @@ -217,6 +217,11 @@ struct mii_bus {
    * matching its address
    */
    int irq[PHY_MAX_ADDR];
    +
    + /* GPIO reset pulse width in uS */
    + int reset_delay_us;
    + /* Number of reset GPIOs */
    + int num_reset_gpios;
    };
    #define to_mii_bus(d) container_of(d, struct mii_bus, dev)

    --
    2.7.4

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