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@@ -1,10 +1,14 @@
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- PHY SUBSYSTEM
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- Kishon Vijay Abraham I <kishon@ti.com>
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+=============
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+PHY subsystem
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+=============
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+
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+:Author: Kishon Vijay Abraham I <kishon@ti.com>
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This document explains the Generic PHY Framework along with the APIs provided,
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and how-to-use.
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-1. Introduction
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+Introduction
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+============
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*PHY* is the abbreviation for physical layer. It is used to connect a device
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to the physical medium e.g., the USB controller has a PHY to provide functions
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@@ -21,7 +25,8 @@ better code maintainability.
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This framework will be of use only to devices that use external PHY (PHY
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functionality is not embedded within the controller).
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-2. Registering/Unregistering the PHY provider
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+Registering/Unregistering the PHY provider
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+==========================================
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PHY provider refers to an entity that implements one or more PHY instances.
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For the simple case where the PHY provider implements only a single instance of
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@@ -30,11 +35,14 @@ of_phy_simple_xlate. If the PHY provider implements multiple instances, it
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should provide its own implementation of of_xlate. of_xlate is used only for
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dt boot case.
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-#define of_phy_provider_register(dev, xlate) \
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- __of_phy_provider_register((dev), NULL, THIS_MODULE, (xlate))
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+::
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+
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+ #define of_phy_provider_register(dev, xlate) \
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+ __of_phy_provider_register((dev), NULL, THIS_MODULE, (xlate))
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-#define devm_of_phy_provider_register(dev, xlate) \
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- __devm_of_phy_provider_register((dev), NULL, THIS_MODULE, (xlate))
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+ #define devm_of_phy_provider_register(dev, xlate) \
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+ __devm_of_phy_provider_register((dev), NULL, THIS_MODULE,
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+ (xlate))
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of_phy_provider_register and devm_of_phy_provider_register macros can be used to
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register the phy_provider and it takes device and of_xlate as
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@@ -47,28 +55,35 @@ nodes within extra levels for context and extensibility, in which case the low
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level of_phy_provider_register_full() and devm_of_phy_provider_register_full()
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macros can be used to override the node containing the children.
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-#define of_phy_provider_register_full(dev, children, xlate) \
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- __of_phy_provider_register(dev, children, THIS_MODULE, xlate)
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+::
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+
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+ #define of_phy_provider_register_full(dev, children, xlate) \
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+ __of_phy_provider_register(dev, children, THIS_MODULE, xlate)
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-#define devm_of_phy_provider_register_full(dev, children, xlate) \
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- __devm_of_phy_provider_register_full(dev, children, THIS_MODULE, xlate)
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+ #define devm_of_phy_provider_register_full(dev, children, xlate) \
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+ __devm_of_phy_provider_register_full(dev, children,
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+ THIS_MODULE, xlate)
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-void devm_of_phy_provider_unregister(struct device *dev,
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- struct phy_provider *phy_provider);
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-void of_phy_provider_unregister(struct phy_provider *phy_provider);
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+ void devm_of_phy_provider_unregister(struct device *dev,
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+ struct phy_provider *phy_provider);
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+ void of_phy_provider_unregister(struct phy_provider *phy_provider);
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devm_of_phy_provider_unregister and of_phy_provider_unregister can be used to
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unregister the PHY.
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-3. Creating the PHY
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+Creating the PHY
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+================
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The PHY driver should create the PHY in order for other peripheral controllers
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to make use of it. The PHY framework provides 2 APIs to create the PHY.
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-struct phy *phy_create(struct device *dev, struct device_node *node,
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- const struct phy_ops *ops);
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-struct phy *devm_phy_create(struct device *dev, struct device_node *node,
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- const struct phy_ops *ops);
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+::
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+
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+ struct phy *phy_create(struct device *dev, struct device_node *node,
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+ const struct phy_ops *ops);
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+ struct phy *devm_phy_create(struct device *dev,
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+ struct device_node *node,
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+ const struct phy_ops *ops);
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The PHY drivers can use one of the above 2 APIs to create the PHY by passing
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the device pointer and phy ops.
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@@ -84,12 +99,16 @@ phy_ops to get back the private data.
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Before the controller can make use of the PHY, it has to get a reference to
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it. This framework provides the following APIs to get a reference to the PHY.
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-struct phy *phy_get(struct device *dev, const char *string);
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-struct phy *phy_optional_get(struct device *dev, const char *string);
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-struct phy *devm_phy_get(struct device *dev, const char *string);
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-struct phy *devm_phy_optional_get(struct device *dev, const char *string);
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-struct phy *devm_of_phy_get_by_index(struct device *dev, struct device_node *np,
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- int index);
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+::
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+
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+ struct phy *phy_get(struct device *dev, const char *string);
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+ struct phy *phy_optional_get(struct device *dev, const char *string);
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+ struct phy *devm_phy_get(struct device *dev, const char *string);
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+ struct phy *devm_phy_optional_get(struct device *dev,
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+ const char *string);
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+ struct phy *devm_of_phy_get_by_index(struct device *dev,
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+ struct device_node *np,
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+ int index);
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phy_get, phy_optional_get, devm_phy_get and devm_phy_optional_get can
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be used to get the PHY. In the case of dt boot, the string arguments
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@@ -111,30 +130,35 @@ the phy_init() and phy_exit() calls, and phy_power_on() and
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phy_power_off() calls are all NOP when applied to a NULL phy. The NULL
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phy is useful in devices for handling optional phy devices.
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-5. Releasing a reference to the PHY
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+Releasing a reference to the PHY
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+================================
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When the controller no longer needs the PHY, it has to release the reference
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to the PHY it has obtained using the APIs mentioned in the above section. The
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PHY framework provides 2 APIs to release a reference to the PHY.
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-void phy_put(struct phy *phy);
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-void devm_phy_put(struct device *dev, struct phy *phy);
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+::
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+
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+ void phy_put(struct phy *phy);
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+ void devm_phy_put(struct device *dev, struct phy *phy);
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Both these APIs are used to release a reference to the PHY and devm_phy_put
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destroys the devres associated with this PHY.
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-6. Destroying the PHY
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+Destroying the PHY
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+==================
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When the driver that created the PHY is unloaded, it should destroy the PHY it
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-created using one of the following 2 APIs.
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+created using one of the following 2 APIs::
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-void phy_destroy(struct phy *phy);
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-void devm_phy_destroy(struct device *dev, struct phy *phy);
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+ void phy_destroy(struct phy *phy);
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+ void devm_phy_destroy(struct device *dev, struct phy *phy);
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Both these APIs destroy the PHY and devm_phy_destroy destroys the devres
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associated with this PHY.
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-7. PM Runtime
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+PM Runtime
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+==========
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This subsystem is pm runtime enabled. So while creating the PHY,
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pm_runtime_enable of the phy device created by this subsystem is called and
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@@ -150,7 +174,8 @@ There are exported APIs like phy_pm_runtime_get, phy_pm_runtime_get_sync,
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phy_pm_runtime_put, phy_pm_runtime_put_sync, phy_pm_runtime_allow and
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phy_pm_runtime_forbid for performing PM operations.
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-8. PHY Mappings
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+PHY Mappings
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+============
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In order to get reference to a PHY without help from DeviceTree, the framework
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offers lookups which can be compared to clkdev that allow clk structures to be
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@@ -158,12 +183,15 @@ bound to devices. A lookup can be made be made during runtime when a handle to
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the struct phy already exists.
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The framework offers the following API for registering and unregistering the
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-lookups.
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+lookups::
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-int phy_create_lookup(struct phy *phy, const char *con_id, const char *dev_id);
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-void phy_remove_lookup(struct phy *phy, const char *con_id, const char *dev_id);
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+ int phy_create_lookup(struct phy *phy, const char *con_id,
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+ const char *dev_id);
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+ void phy_remove_lookup(struct phy *phy, const char *con_id,
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+ const char *dev_id);
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-9. DeviceTree Binding
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+DeviceTree Binding
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+==================
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The documentation for PHY dt binding can be found @
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Documentation/devicetree/bindings/phy/phy-bindings.txt
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