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.. SPDX-License-Identifier: GPL-2.0-or-later
.. Luigi 'Comio' Mantellini <luigi.mantellini@idf-hit.com>, Industrie Dial Face S.p.A., 2009
Bit-banged MII bus support
==========================
The miiphybb ( Bit-banged MII bus driver ) supports an arbitrary number of
MII buses. This feature is useful when a driver uses different MII buses for
different PHYs and all (or a part) of these buses are implemented via
bit-banging mode.
The driver requires that the following macro is defined in the board
configuration file:
* CONFIG_BITBANGMII - Enable the miiphybb driver
The driver code needs to allocate a regular MDIO device using mdio_alloc()
and assign .read and .write accessors which wrap bb_miiphy_read() and
bb_miiphy_write() functions respectively. The bb_miiphy_read() and
bb_miiphy_write() functions take a pointer to a callback structure,
struct bb_miiphy_bus_ops. The struct bb_miiphy_bus_ops has the following
fields/callbacks (see miiphy.h for details):
.. code-block:: c
int (*mdio_active)() // Activate the MDIO pin as output
int (*mdio_tristate)() // Activate the MDIO pin as input/tristate pin
int (*set_mdio)() // Write the MDIO pin
int (*get_mdio)() // Read the MDIO pin
int (*set_mdc)() // Write the MDC pin
int (*delay)() // Delay function
The driver code will look like:
.. code-block:: c
static const struct bb_miiphy_bus_ops ravb_bb_miiphy_bus_ops = {
.mdio_active = ravb_bb_mdio_active,
.mdio_tristate = ravb_bb_mdio_tristate,
.set_mdio = ravb_bb_set_mdio,
.get_mdio = ravb_bb_get_mdio,
.set_mdc = ravb_bb_set_mdc,
.delay = ravb_bb_delay,
};
static int ravb_bb_miiphy_read(struct mii_dev *miidev, int addr,
int devad, int reg)
{
return bb_miiphy_read(miidev, &ravb_bb_miiphy_bus_ops,
addr, devad, reg);
}
static int ravb_bb_miiphy_write(struct mii_dev *miidev, int addr,
int devad, int reg, u16 value)
{
return bb_miiphy_write(miidev, &ravb_bb_miiphy_bus_ops,
addr, devad, reg, value);
}
static int ravb_probe(struct udevice *dev)
{
struct mii_dev *mdiodev;
...
mdiodev = mdio_alloc();
if (!mdiodev)
return -ENOMEM;
mdiodev->read = ravb_bb_miiphy_read;
mdiodev->write = ravb_bb_miiphy_write;
mdiodev->priv = eth;
snprintf(mdiodev->name, sizeof(mdiodev->name), dev->name);
ret = mdio_register(mdiodev);
...
}
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