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    SubjectRe: [PATCH 2/3] netdev/of/phy: Add MDIO bus multiplexer support.
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    > diff --git a/Documentation/devicetree/bindings/net/mdio-mux.txt b/Documentation/devicetree/bindings/net/mdio-mux.txt
    > new file mode 100644
    > index 0000000..a908312
    > --- /dev/null
    > +++ b/Documentation/devicetree/bindings/net/mdio-mux.txt
    > @@ -0,0 +1,132 @@
    > +Common MDIO bus multiplexer/switch properties.
    > +
    > +An MDIO bus multiplexer/switch will have several child busses that are
    > +numbered uniquely in a device dependent manner. The nodes for an MDIO
    > +bus multiplexer/switch will have one child node for each child bus.
    > +
    > +Required properties:
    > +- parent-bus : phandle to the parent MDIO bus.

    Should probably be mdio-parent-bus

    > +
    > +Optional properties:
    > +- Other properties specific to the multiplexer/switch hardware.
    > +
    > +Required properties for child nodes:
    > +- #address-cells = <1>;
    > +- #size-cells = <0>;
    > +- cell-index : The sub-bus number.

    What does sub-bus number mean?

    > +
    > +
    > +Example :

    [snip]

    > diff --git a/drivers/net/phy/mdio-mux.c b/drivers/net/phy/mdio-mux.c
    > new file mode 100644
    > index 0000000..f9c5826
    > --- /dev/null
    > +++ b/drivers/net/phy/mdio-mux.c
    > @@ -0,0 +1,182 @@
    > +/*
    > + * This file is subject to the terms and conditions of the GNU General Public
    > + * License. See the file "COPYING" in the main directory of this archive
    > + * for more details.
    > + *
    > + * Copyright (C) 2011 Cavium Networks
    > + */
    > +
    > +#include <linux/platform_device.h>
    > +#include <linux/of_mdio.h>
    > +#include <linux/module.h>
    > +#include <linux/init.h>
    > +#include <linux/gfp.h>
    > +#include <linux/phy.h>
    > +#include <linux/mdio-mux.h>
    > +
    > +#define DRV_VERSION "1.0"
    > +#define DRV_DESCRIPTION "MDIO bus multiplexer driver"
    > +
    > +struct mdio_mux_parent_bus {
    > + struct mii_bus *mii_bus;
    > + int current_child;
    > + int parent_id;
    > + void *switch_data;
    > + int (*switch_fn)(int current_child, int desired_child, void *data);
    > +};
    > +
    > +struct mdio_mux_child_bus {
    > + struct mii_bus *mii_bus;
    > + struct mdio_mux_parent_bus *parent;
    > + int bus_number;
    > + int phy_irq[PHY_MAX_ADDR];
    > +};
    > +
    > +/*
    > + * The parent bus' lock is used to order access to the switch_fn.
    > + */
    > +static int mdio_mux_read(struct mii_bus *bus, int phy_id, int regnum)
    > +{
    > + struct mdio_mux_child_bus *cb = bus->priv;
    > + struct mdio_mux_parent_bus *pb = cb->parent;
    > + int r;
    > +
    > + mutex_lock(&pb->mii_bus->mdio_lock);
    > + r = pb->switch_fn(pb->current_child, cb->bus_number, pb->switch_data);
    > + if (r)
    > + goto out;
    > +
    > + pb->current_child = cb->bus_number;
    > +
    > + r = pb->mii_bus->read(pb->mii_bus, phy_id, regnum);
    > +out:
    > + mutex_unlock(&pb->mii_bus->mdio_lock);
    > +
    > + return r;
    > +}
    > +
    > +/*
    > + * The parent bus' lock is used to order access to the switch_fn.
    > + */
    > +static int mdio_mux_write(struct mii_bus *bus, int phy_id,
    > + int regnum, u16 val)
    > +{
    > + struct mdio_mux_child_bus *cb = bus->priv;
    > + struct mdio_mux_parent_bus *pb = cb->parent;
    > +
    > + int r;
    > +
    > + mutex_lock(&pb->mii_bus->mdio_lock);
    > + r = pb->switch_fn(pb->current_child, cb->bus_number, pb->switch_data);
    > + if (r)
    > + goto out;
    > +
    > + pb->current_child = cb->bus_number;
    > +
    > + r = pb->mii_bus->write(pb->mii_bus, phy_id, regnum, val);
    > +out:
    > + mutex_unlock(&pb->mii_bus->mdio_lock);
    > +
    > + return r;
    > +}
    > +
    > +static int parent_count;
    > +
    > +int mdio_mux_probe(struct platform_device *pdev,
    > + int (*switch_fn)(int cur, int desired, void *data),
    > + void *data)
    > +{
    > + struct device_node *parent_bus_node;
    > + struct device_node *child_bus_node;
    > + int r, n, ret_val;
    > + struct mii_bus *parent_bus;
    > + struct mdio_mux_parent_bus *pb;
    > + struct mdio_mux_child_bus *cb;
    > +
    > + if (!pdev->dev.of_node)
    > + return -ENODEV;
    > +
    > + parent_bus_node = of_parse_phandle(pdev->dev.of_node, "parent-bus", 0);
    > +
    > + if (!parent_bus_node)
    > + return -ENODEV;
    > +
    > + parent_bus = of_mdio_find_bus(parent_bus_node);


    So what happens if the parent bus probe happens after the mux probe?

    > +
    > + pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
    > + if (pb == NULL) {
    > + ret_val = -ENOMEM;
    > + goto err_parent_bus;
    > + }
    > +
    > + pb->switch_data = data;
    > + pb->switch_fn = switch_fn;
    > + pb->current_child = -1;
    > + pb->parent_id = parent_count++;
    > + pb->mii_bus = parent_bus;
    > +
    > + n = 0;
    > + for_each_child_of_node(pdev->dev.of_node, child_bus_node) {
    > + u32 v;
    > +
    > + r = of_property_read_u32(child_bus_node, "cell-index", &v);
    > + if (r == 0) {
    > + cb = devm_kzalloc(&pdev->dev, sizeof(*cb), GFP_KERNEL);
    > + if (cb == NULL)
    > + break;
    > + cb->bus_number = v;
    > + cb->parent = pb;
    > + cb->mii_bus = mdiobus_alloc();
    > + cb->mii_bus->priv = cb;
    > +
    > + cb->mii_bus->irq = cb->phy_irq;
    > + cb->mii_bus->name = "mdio_mux";
    > + snprintf(cb->mii_bus->id, MII_BUS_ID_SIZE, "%x.%x",
    > + pb->parent_id, v);
    > + cb->mii_bus->parent = &pdev->dev;
    > + cb->mii_bus->read = mdio_mux_read;
    > + cb->mii_bus->write = mdio_mux_write;
    > + r = of_mdiobus_register(cb->mii_bus, child_bus_node);
    > + if (r) {
    > + of_node_put(child_bus_node);
    > + devm_kfree(&pdev->dev, cb);
    > + } else {
    > + n++;
    > + }
    > +
    > + } else {
    > + of_node_put(child_bus_node);
    > + }
    > + }
    > + if (n) {
    > + dev_info(&pdev->dev, "Version " DRV_VERSION "\n");
    > + return 0;
    > + }
    > + ret_val = -ENOMEM;
    > + devm_kfree(&pdev->dev, pb);
    > +err_parent_bus:
    > + of_node_put(parent_bus_node);
    > + return ret_val;
    > +}
    > +EXPORT_SYMBOL(mdio_mux_probe);
    > +
    > +static int __devexit mdio_mux_remove(struct platform_device *pdev)
    > +{
    > + return 0;
    > +}
    > +
    > +static int __init mdio_mux_mod_init(void)
    > +{
    > + return 0;
    > +}
    > +module_init(mdio_mux_mod_init);
    > +
    > +static void __exit mdio_mux_mod_exit(void)
    > +{
    > +}
    > +module_exit(mdio_mux_mod_exit);
    > +
    > +MODULE_DESCRIPTION(DRV_DESCRIPTION);
    > +MODULE_VERSION(DRV_VERSION);
    > +MODULE_AUTHOR("David Daney");
    > +MODULE_LICENSE("GPL");




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