linux/Documentation/devicetree/bindings/net/mdio.txt
Roger Quadros 69226896ad 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>
2017-04-24 12:40:24 -04:00

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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>;
};
};