Re: [PATCH v2 2/3] netdev/of/phy: Add MDIO bus multiplexer support.

[Grant Likely]

On Tue, Sep 27, 2011 at 04:26:54PM -0700, David Daney wrote:
> This patch adds a somewhat generic framework for MDIO bus
> multiplexers.  It is modeled on the I2C multiplexer.
> 
> The multiplexer is needed if there are multiple PHYs with the same
> address connected to the same MDIO bus adepter, or if there is
> insufficient electrical drive capability for all the connected PHY
> devices.
> 
> Conceptually it could look something like this:
> 
>                    ------------------
>                    | Control Signal |
>                    --------+---------
>                            |
>  ---------------   --------+------
>  | MDIO MASTER |---| Multiplexer |
>  ---------------   --+-------+----
>                      |       |
>                      C       C
>                      h       h
>                      i       i
>                      l       l
>                      d       d
>                      |       |
>      ---------       A       B   ---------
>      |       |       |       |   |       |
>      | PHY@1 +-------+       +---+ PHY@1 |
>      |       |       |       |   |       |
>      ---------       |       |   ---------
>      ---------       |       |   ---------
>      |       |       |       |   |       |
>      | PHY@2 +-------+       +---+ PHY@2 |
>      |       |                   |       |
>      ---------                   ---------
> 
> This framework configures the bus topology from device tree data.  The
> mechanics of switching the multiplexer is left to device specific
> drivers.
> 
> The follow-on patch contains a multiplexer driven by GPIO lines.
> 
> Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
> Acked-by: Andy Fleming <afleming@xxxxxxxxxxxxx>
> Cc: Grant Likely <grant.likely@xxxxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> ---
>  Documentation/devicetree/bindings/net/mdio-mux.txt |  136 +++++++++++++++
>  drivers/net/phy/Kconfig                            |    8 +
>  drivers/net/phy/Makefile                           |    1 +
>  drivers/net/phy/mdio-mux.c                         |  182 ++++++++++++++++++++
>  include/linux/mdio-mux.h                           |   18 ++
>  5 files changed, 345 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/net/mdio-mux.txt
>  create mode 100644 drivers/net/phy/mdio-mux.c
>  create mode 100644 include/linux/mdio-mux.h
> 
> diff --git a/Documentation/devicetree/bindings/net/mdio-mux.txt b/Documentation/devicetree/bindings/net/mdio-mux.txt
> new file mode 100644
> index 0000000..5acba65
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/net/mdio-mux.txt
> @@ -0,0 +1,136 @@
> +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:
> +- mdio-parent-bus : phandle to the parent MDIO bus.
> +- #address-cells = <1>;
> +- #size-cells = <0>;
> +
> +Optional properties:
> +- Other properties specific to the multiplexer/switch hardware.
> +
> +Required properties for child nodes:
> +- #address-cells = <1>;
> +- #size-cells = <0>;
> +- reg : The sub-bus number.
> +
> +
> +Example :
> +
> +	/* The parent MDIO bus. */
> +	smi1: mdio@1180000001900 {
> +		compatible = "cavium,octeon-3860-mdio";
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +		reg = <0x11800 0x00001900 0x0 0x40>;
> +	};
> +
> +	/*
> +	   An NXP sn74cbtlv3253 dual 1-of-4 switch controlled by a
> +	   pair of GPIO lines.  Child busses 2 and 3 populated with 4
> +	   PHYs each.
> +	 */
> +	mdio-mux {
> +		compatible = "cavium,mdio-mux-sn74cbtlv3253", "cavium,mdio-mux";
> +		gpios = <&gpio1 3 0>, <&gpio1 4 0>;
> +		mdio-parent-bus = <&smi1>;
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +
> +		mdio@2 {
> +			reg = <2>;
> +			#address-cells = <1>;
> +			#size-cells = <0>;
> +
> +			phy11: ethernet-phy@1 {
> +				reg = <1>;
> +				compatible = "marvell,88e1149r";
> +				marvell,reg-init = <3 0x10 0 0x5777>,
> +					<3 0x11 0 0x00aa>,
> +					<3 0x12 0 0x4105>,
> +					<3 0x13 0 0x0a60>;
> +				interrupt-parent = <&gpio>;
> +				interrupts = <10 8>; /* Pin 10, active low */
> +			};
> +			phy12: ethernet-phy@2 {
> +				reg = <2>;
> +				compatible = "marvell,88e1149r";
> +				marvell,reg-init = <3 0x10 0 0x5777>,
> +					<3 0x11 0 0x00aa>,
> +					<3 0x12 0 0x4105>,
> +					<3 0x13 0 0x0a60>;
> +				interrupt-parent = <&gpio>;
> +				interrupts = <10 8>; /* Pin 10, active low */
> +			};
> +			phy13: ethernet-phy@3 {
> +				reg = <3>;
> +				compatible = "marvell,88e1149r";
> +				marvell,reg-init = <3 0x10 0 0x5777>,
> +					<3 0x11 0 0x00aa>,
> +					<3 0x12 0 0x4105>,
> +					<3 0x13 0 0x0a60>;
> +				interrupt-parent = <&gpio>;
> +				interrupts = <10 8>; /* Pin 10, active low */
> +			};
> +			phy14: ethernet-phy@4 {
> +				reg = <4>;
> +				compatible = "marvell,88e1149r";
> +				marvell,reg-init = <3 0x10 0 0x5777>,
> +					<3 0x11 0 0x00aa>,
> +					<3 0x12 0 0x4105>,
> +					<3 0x13 0 0x0a60>;
> +				interrupt-parent = <&gpio>;
> +				interrupts = <10 8>; /* Pin 10, active low */
> +			};
> +		};
> +
> +		mdio@3 {
> +			reg = <3>;
> +			#address-cells = <1>;
> +			#size-cells = <0>;
> +
> +			phy21: ethernet-phy@1 {
> +				reg = <1>;
> +				compatible = "marvell,88e1149r";
> +				marvell,reg-init = <3 0x10 0 0x5777>,
> +					<3 0x11 0 0x00aa>,
> +					<3 0x12 0 0x4105>,
> +					<3 0x13 0 0x0a60>;
> +				interrupt-parent = <&gpio>;
> +				interrupts = <12 8>; /* Pin 12, active low */
> +			};
> +			phy22: ethernet-phy@2 {
> +				reg = <2>;
> +				compatible = "marvell,88e1149r";
> +				marvell,reg-init = <3 0x10 0 0x5777>,
> +					<3 0x11 0 0x00aa>,
> +					<3 0x12 0 0x4105>,
> +					<3 0x13 0 0x0a60>;
> +				interrupt-parent = <&gpio>;
> +				interrupts = <12 8>; /* Pin 12, active low */
> +			};
> +			phy23: ethernet-phy@3 {
> +				reg = <3>;
> +				compatible = "marvell,88e1149r";
> +				marvell,reg-init = <3 0x10 0 0x5777>,
> +					<3 0x11 0 0x00aa>,
> +					<3 0x12 0 0x4105>,
> +					<3 0x13 0 0x0a60>;
> +				interrupt-parent = <&gpio>;
> +				interrupts = <12 8>; /* Pin 12, active low */
> +			};
> +			phy24: ethernet-phy@4 {
> +				reg = <4>;
> +				compatible = "marvell,88e1149r";
> +				marvell,reg-init = <3 0x10 0 0x5777>,
> +					<3 0x11 0 0x00aa>,
> +					<3 0x12 0 0x4105>,
> +					<3 0x13 0 0x0a60>;
> +				interrupt-parent = <&gpio>;
> +				interrupts = <12 8>; /* Pin 12, active low */
> +			};
> +		};
> +	};
> diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
> index a702443..59848bc 100644
> --- a/drivers/net/phy/Kconfig
> +++ b/drivers/net/phy/Kconfig
> @@ -119,6 +119,14 @@ config MDIO_GPIO
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called mdio-gpio.
>  
> +config MDIO_BUS_MUX
> +	tristate "Support for MDIO bus multiplexers"
> +	help
> +	  This module provides a driver framework for MDIO bus
> +	  multiplexers which connect one of several child MDIO busses
> +	  to a parent bus.  Switching between child busses is done by
> +	  device specific drivers.
> +

Don't make this a user visible option.  Make the bus driver select it.

>  config MDIO_OCTEON
>  	tristate "Support for MDIO buses on Octeon SOCs"
>  	depends on  CPU_CAVIUM_OCTEON
> diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
> index 2333215..0c081d5 100644
> --- a/drivers/net/phy/Makefile
> +++ b/drivers/net/phy/Makefile
> @@ -23,3 +23,4 @@ obj-$(CONFIG_DP83640_PHY)	+= dp83640.o
>  obj-$(CONFIG_STE10XP)		+= ste10Xp.o
>  obj-$(CONFIG_MICREL_PHY)	+= micrel.o
>  obj-$(CONFIG_MDIO_OCTEON)	+= mdio-octeon.o
> +obj-$(CONFIG_MDIO_BUS_MUX)	+= mdio-mux.o
> diff --git a/drivers/net/phy/mdio-mux.c b/drivers/net/phy/mdio-mux.c
> new file mode 100644
> index 0000000..a940296
> --- /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)
> +{

Don't call this probe.  Probe typically means top level driver, but
this module is a library used by MDIO mux drivers.  Call this
functions something like init.  Also, passing it a platform_device
looks wrong since it might be a platform_device, but it might be an
i2c_client or an spi_device.  Pass in struct device instead.

Also, this function should return the pointer to the allocated
mdio_mux_parent_bus so that the calling driver has a reference to it.

> +	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, "mdio-parent-bus", 0);
> +
> +	if (!parent_bus_node)
> +		return -ENODEV;
> +
> +	parent_bus = of_mdio_find_bus(parent_bus_node);

What if of_mdio_find_bus() fails?

> +
> +	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, "reg", &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;

The parent bus should probably maintain a list of all child busses so
that a shutdown function can tear it all down again.

> +			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);

I don't believe that you need module empty module init/exit/remove
routines.  Just drop them.

> +
> +MODULE_DESCRIPTION(DRV_DESCRIPTION);
> +MODULE_VERSION(DRV_VERSION);
> +MODULE_AUTHOR("David Daney");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/mdio-mux.h b/include/linux/mdio-mux.h
> new file mode 100644
> index 0000000..522992a
> --- /dev/null
> +++ b/include/linux/mdio-mux.h
> @@ -0,0 +1,18 @@
> +/*
> + * MDIO bus multiplexer framwork.
> + *
> + * 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
> + */
> +#ifndef __LINUX_MDIO_MUX_H
> +#define __LINUX_MDIO_MUX_H
> +#include <linux/platform_device.h>
> +
> +int mdio_mux_probe(struct platform_device *pdev,
> +		   int (*switch_fn) (int cur, int desired, void *data),
> +		   void *data);
> +
> +#endif /* __LINUX_MDIO_MUX_H */
> -- 
> 1.7.2.3
> 
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