Commit 5426a2cc authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab Committed by Jonathan Corbet

phy.txt: standardize document format

Each text file under Documentation follows a different
format. Some doesn't even have titles!

Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx:

- mark titles;
- use :Author: for authorship;
- mark literal blocks.
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent c437c3a4
PHY SUBSYSTEM
Kishon Vijay Abraham I <kishon@ti.com>
=============
PHY subsystem
=============
:Author: 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
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
......@@ -21,7 +25,8 @@ 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
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
......@@ -30,11 +35,14 @@ 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), NULL, THIS_MODULE, (xlate))
::
#define of_phy_provider_register(dev, xlate) \
__of_phy_provider_register((dev), NULL, THIS_MODULE, (xlate))
#define devm_of_phy_provider_register(dev, xlate) \
__devm_of_phy_provider_register((dev), NULL, THIS_MODULE, (xlate))
#define devm_of_phy_provider_register(dev, xlate) \
__devm_of_phy_provider_register((dev), NULL, 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
......@@ -47,28 +55,35 @@ nodes within extra levels for context and extensibility, in which case the low
level of_phy_provider_register_full() and devm_of_phy_provider_register_full()
macros can be used to override the node containing the children.
#define of_phy_provider_register_full(dev, children, xlate) \
__of_phy_provider_register(dev, children, THIS_MODULE, xlate)
::
#define of_phy_provider_register_full(dev, children, xlate) \
__of_phy_provider_register(dev, children, THIS_MODULE, xlate)
#define devm_of_phy_provider_register_full(dev, children, xlate) \
__devm_of_phy_provider_register_full(dev, children, THIS_MODULE, xlate)
#define devm_of_phy_provider_register_full(dev, children, xlate) \
__devm_of_phy_provider_register_full(dev, children,
THIS_MODULE, xlate)
void devm_of_phy_provider_unregister(struct device *dev,
struct phy_provider *phy_provider);
void of_phy_provider_unregister(struct phy_provider *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
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, struct device_node *node,
const struct phy_ops *ops);
struct phy *devm_phy_create(struct device *dev, struct device_node *node,
const struct phy_ops *ops);
::
struct phy *phy_create(struct device *dev, struct device_node *node,
const struct phy_ops *ops);
struct phy *devm_phy_create(struct device *dev,
struct device_node *node,
const struct phy_ops *ops);
The PHY drivers can use one of the above 2 APIs to create the PHY by passing
the device pointer and phy ops.
......@@ -84,12 +99,16 @@ phy_ops to get back the private data.
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 *phy_optional_get(struct device *dev, const char *string);
struct phy *devm_phy_get(struct device *dev, const char *string);
struct phy *devm_phy_optional_get(struct device *dev, const char *string);
struct phy *devm_of_phy_get_by_index(struct device *dev, struct device_node *np,
int index);
::
struct phy *phy_get(struct device *dev, const char *string);
struct phy *phy_optional_get(struct device *dev, const char *string);
struct phy *devm_phy_get(struct device *dev, const char *string);
struct phy *devm_phy_optional_get(struct device *dev,
const char *string);
struct phy *devm_of_phy_get_by_index(struct device *dev,
struct device_node *np,
int index);
phy_get, phy_optional_get, devm_phy_get and devm_phy_optional_get can
be used to get the PHY. In the case of dt boot, the string arguments
......@@ -111,30 +130,35 @@ the phy_init() and phy_exit() calls, and phy_power_on() and
phy_power_off() calls are all NOP when applied to a NULL phy. The NULL
phy is useful in devices for handling optional phy devices.
5. Releasing a reference to the PHY
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);
::
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
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.
created using one of the following 2 APIs::
void phy_destroy(struct phy *phy);
void devm_phy_destroy(struct device *dev, struct phy *phy);
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
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
......@@ -150,7 +174,8 @@ 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. PHY Mappings
PHY Mappings
============
In order to get reference to a PHY without help from DeviceTree, the framework
offers lookups which can be compared to clkdev that allow clk structures to be
......@@ -158,12 +183,15 @@ bound to devices. A lookup can be made be made during runtime when a handle to
the struct phy already exists.
The framework offers the following API for registering and unregistering the
lookups.
lookups::
int phy_create_lookup(struct phy *phy, const char *con_id, const char *dev_id);
void phy_remove_lookup(struct phy *phy, const char *con_id, const char *dev_id);
int phy_create_lookup(struct phy *phy, const char *con_id,
const char *dev_id);
void phy_remove_lookup(struct phy *phy, const char *con_id,
const char *dev_id);
9. DeviceTree Binding
DeviceTree Binding
==================
The documentation for PHY dt binding can be found @
Documentation/devicetree/bindings/phy/phy-bindings.txt
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