drivers: phy: add generic PHY framework

This document explains only the device tree data binding. For general

information about PHY subsystem refer to Documentation/phy.txt

PHY device node

===============

Required Properties:

#phy-cells:	Number of cells in a PHY specifier;  The meaning of all those

		cells is defined by the binding for the phy node. The PHY

		provider can use the values in cells to find the appropriate

		PHY.

For example:

phys: phy {

    compatible = "xxx";

    reg = <...>;

    .

    .

    #phy-cells = <1>;

    .

    .

};

That node describes an IP block (PHY provider) that implements 2 different PHYs.

In order to differentiate between these 2 PHYs, an additonal specifier should be

given while trying to get a reference to it.

PHY user node

=============

Required Properties:

phys : the phandle for the PHY device (used by the PHY subsystem)

phy-names : the names of the PHY corresponding to the PHYs present in the

	    *phys* phandle

Example 1:

usb1: usb_otg_ss@xxx {

    compatible = "xxx";

    reg = <xxx>;

    .

    .

    phys = <&usb2_phy>, <&usb3_phy>;

    phy-names = "usb2phy", "usb3phy";

    .

    .

};

This node represents a controller that uses two PHYs, one for usb2 and one for

usb3.

Example 2:

usb2: usb_otg_ss@xxx {

    compatible = "xxx";

    reg = <xxx>;

    .

    .

    phys = <&phys 1>;

    phy-names = "usbphy";

    .

    .

};

This node represents a controller that uses one of the PHYs of the PHY provider

device defined previously. Note that the phy handle has an additional specifier

"1" to differentiate between the two PHYs.

			    PHY SUBSYSTEM

		  Kishon Vijay Abraham I <kishon@ti.com>

This document explains the Generic PHY Framework along with the APIs provided,

and how-to-use.

1. Introduction

*PHY* is the abbreviation for physical layer. It is used to connect a device

to the physical medium e.g., the USB controller has a PHY to provide functions

such as serialization, de-serialization, encoding, decoding and is responsible

for obtaining the required data transmission rate. Note that some USB

controllers have PHY functionality embedded into it and others use an external

PHY. Other peripherals that use PHY include Wireless LAN, Ethernet,

SATA etc.

The intention of creating this framework is to bring the PHY drivers spread

all over the Linux kernel to drivers/phy to increase code re-use and for

better code maintainability.

This framework will be of use only to devices that use external PHY (PHY

functionality is not embedded within the controller).

2. Registering/Unregistering the PHY provider

PHY provider refers to an entity that implements one or more PHY instances.

For the simple case where the PHY provider implements only a single instance of

the PHY, the framework provides its own implementation of of_xlate in

of_phy_simple_xlate. If the PHY provider implements multiple instances, it

should provide its own implementation of of_xlate. of_xlate is used only for

dt boot case.

#define of_phy_provider_register(dev, xlate)    \

        __of_phy_provider_register((dev), THIS_MODULE, (xlate))

#define devm_of_phy_provider_register(dev, xlate)       \

        __devm_of_phy_provider_register((dev), THIS_MODULE, (xlate))

of_phy_provider_register and devm_of_phy_provider_register macros can be used to

register the phy_provider and it takes device and of_xlate as

arguments. For the dt boot case, all PHY providers should use one of the above

2 macros to register the PHY provider.

void devm_of_phy_provider_unregister(struct device *dev,

	struct phy_provider *phy_provider);

void of_phy_provider_unregister(struct phy_provider *phy_provider);

devm_of_phy_provider_unregister and of_phy_provider_unregister can be used to

unregister the PHY.

3. Creating the PHY

The PHY driver should create the PHY in order for other peripheral controllers

to make use of it. The PHY framework provides 2 APIs to create the PHY.

struct phy *phy_create(struct device *dev, const struct phy_ops *ops,

        struct phy_init_data *init_data);

struct phy *devm_phy_create(struct device *dev, const struct phy_ops *ops,

	struct phy_init_data *init_data);

The PHY drivers can use one of the above 2 APIs to create the PHY by passing

the device pointer, phy ops and init_data.

phy_ops is a set of function pointers for performing PHY operations such as

init, exit, power_on and power_off. *init_data* is mandatory to get a reference

to the PHY in the case of non-dt boot. See section *Board File Initialization*

on how init_data should be used.

Inorder to dereference the private data (in phy_ops), the phy provider driver

can use phy_set_drvdata() after creating the PHY and use phy_get_drvdata() in

phy_ops to get back the private data.

4. Getting a reference to the PHY

Before the controller can make use of the PHY, it has to get a reference to

it. This framework provides the following APIs to get a reference to the PHY.

struct phy *phy_get(struct device *dev, const char *string);

struct phy *devm_phy_get(struct device *dev, const char *string);

phy_get and devm_phy_get can be used to get the PHY. In the case of dt boot,

the string arguments should contain the phy name as given in the dt data and

in the case of non-dt boot, it should contain the label of the PHY.

The only difference between the two APIs is that devm_phy_get associates the

device with the PHY using devres on successful PHY get. On driver detach,

release function is invoked on the the devres data and devres data is freed.

5. Releasing a reference to the PHY

When the controller no longer needs the PHY, it has to release the reference

to the PHY it has obtained using the APIs mentioned in the above section. The

PHY framework provides 2 APIs to release a reference to the PHY.

void phy_put(struct phy *phy);

void devm_phy_put(struct device *dev, struct phy *phy);

Both these APIs are used to release a reference to the PHY and devm_phy_put

destroys the devres associated with this PHY.

6. Destroying the PHY

When the driver that created the PHY is unloaded, it should destroy the PHY it

created using one of the following 2 APIs.

void phy_destroy(struct phy *phy);

void devm_phy_destroy(struct device *dev, struct phy *phy);

Both these APIs destroy the PHY and devm_phy_destroy destroys the devres

associated with this PHY.

7. PM Runtime

This subsystem is pm runtime enabled. So while creating the PHY,

pm_runtime_enable of the phy device created by this subsystem is called and

while destroying the PHY, pm_runtime_disable is called. Note that the phy

device created by this subsystem will be a child of the device that calls

phy_create (PHY provider device).

So pm_runtime_get_sync of the phy_device created by this subsystem will invoke

pm_runtime_get_sync of PHY provider device because of parent-child relationship.

It should also be noted that phy_power_on and phy_power_off performs

phy_pm_runtime_get_sync and phy_pm_runtime_put respectively.

There are exported APIs like phy_pm_runtime_get, phy_pm_runtime_get_sync,

phy_pm_runtime_put, phy_pm_runtime_put_sync, phy_pm_runtime_allow and

phy_pm_runtime_forbid for performing PM operations.

8. Board File Initialization

Certain board file initialization is necessary in order to get a reference

to the PHY in the case of non-dt boot.

Say we have a single device that implements 3 PHYs that of USB, SATA and PCIe,

then in the board file the following initialization should be done.

struct phy_consumer consumers[] = {

	PHY_CONSUMER("dwc3.0", "usb"),

	PHY_CONSUMER("pcie.0", "pcie"),

	PHY_CONSUMER("sata.0", "sata"),

};

PHY_CONSUMER takes 2 parameters, first is the device name of the controller

(PHY consumer) and second is the port name.

struct phy_init_data init_data = {

	.consumers = consumers,

	.num_consumers = ARRAY_SIZE(consumers),

};

static const struct platform_device pipe3_phy_dev = {

	.name = "pipe3-phy",

	.id = -1,

	.dev = {

		.platform_data = {

			.init_data = &init_data,

		},

	},

};

then, while doing phy_create, the PHY driver should pass this init_data

	phy_create(dev, ops, pdata->init_data);

and the controller driver (phy consumer) should pass the port name along with

the device to get a reference to the PHY

	phy_get(dev, "pcie");

9. DeviceTree Binding

The documentation for PHY dt binding can be found @

Documentation/devicetree/bindings/phy/phy-bindings.txt

F:	include/asm-generic/

F:	include/uapi/asm-generic/

GENERIC PHY FRAMEWORK

M:	Kishon Vijay Abraham I <kishon@ti.com>

L:	linux-kernel@vger.kernel.org

T:	git git://git.kernel.org/pub/scm/linux/kernel/git/kishon/linux-phy.git

S:	Supported

F:	drivers/phy/

F:	include/linux/phy/

GENERIC UIO DRIVER FOR PCI DEVICES

M:	"Michael S. Tsirkin" <mst@redhat.com>

L:	kvm@vger.kernel.org

source "drivers/fmc/Kconfig"

source "drivers/phy/Kconfig"

endmenu

obj-y				+= irqchip/

obj-y				+= bus/

obj-$(CONFIG_GENERIC_PHY)	+= phy/

# GPIO must come after pinctrl as gpios may need to mux pins etc

obj-y				+= pinctrl/

obj-y				+= gpio/