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Kishon Vijay Abraham Iff764962013-09-27 11:53:25 +05301 PHY SUBSYSTEM
2 Kishon Vijay Abraham I <kishon@ti.com>
3
4This document explains the Generic PHY Framework along with the APIs provided,
5and how-to-use.
6
71. Introduction
8
9*PHY* is the abbreviation for physical layer. It is used to connect a device
10to the physical medium e.g., the USB controller has a PHY to provide functions
11such as serialization, de-serialization, encoding, decoding and is responsible
12for obtaining the required data transmission rate. Note that some USB
13controllers have PHY functionality embedded into it and others use an external
14PHY. Other peripherals that use PHY include Wireless LAN, Ethernet,
15SATA etc.
16
17The intention of creating this framework is to bring the PHY drivers spread
18all over the Linux kernel to drivers/phy to increase code re-use and for
19better code maintainability.
20
21This framework will be of use only to devices that use external PHY (PHY
22functionality is not embedded within the controller).
23
242. Registering/Unregistering the PHY provider
25
26PHY provider refers to an entity that implements one or more PHY instances.
27For the simple case where the PHY provider implements only a single instance of
28the PHY, the framework provides its own implementation of of_xlate in
29of_phy_simple_xlate. If the PHY provider implements multiple instances, it
30should provide its own implementation of of_xlate. of_xlate is used only for
31dt boot case.
32
33#define of_phy_provider_register(dev, xlate) \
34 __of_phy_provider_register((dev), THIS_MODULE, (xlate))
35
36#define devm_of_phy_provider_register(dev, xlate) \
37 __devm_of_phy_provider_register((dev), THIS_MODULE, (xlate))
38
39of_phy_provider_register and devm_of_phy_provider_register macros can be used to
40register the phy_provider and it takes device and of_xlate as
41arguments. For the dt boot case, all PHY providers should use one of the above
422 macros to register the PHY provider.
43
44void devm_of_phy_provider_unregister(struct device *dev,
45 struct phy_provider *phy_provider);
46void of_phy_provider_unregister(struct phy_provider *phy_provider);
47
48devm_of_phy_provider_unregister and of_phy_provider_unregister can be used to
49unregister the PHY.
50
513. Creating the PHY
52
53The PHY driver should create the PHY in order for other peripheral controllers
54to make use of it. The PHY framework provides 2 APIs to create the PHY.
55
Kishon Vijay Abraham If0ed8172014-07-14 15:55:02 +053056struct phy *phy_create(struct device *dev, struct device_node *node,
Heikki Krogerusb7bc15b2014-11-19 17:28:18 +020057 const struct phy_ops *ops);
Kishon Vijay Abraham If0ed8172014-07-14 15:55:02 +053058struct phy *devm_phy_create(struct device *dev, struct device_node *node,
Heikki Krogerusb7bc15b2014-11-19 17:28:18 +020059 const struct phy_ops *ops);
Kishon Vijay Abraham Iff764962013-09-27 11:53:25 +053060
61The PHY drivers can use one of the above 2 APIs to create the PHY by passing
Heikki Krogerusb7bc15b2014-11-19 17:28:18 +020062the device pointer and phy ops.
Kishon Vijay Abraham Iff764962013-09-27 11:53:25 +053063phy_ops is a set of function pointers for performing PHY operations such as
Heikki Krogerusb7bc15b2014-11-19 17:28:18 +020064init, exit, power_on and power_off.
Kishon Vijay Abraham Iff764962013-09-27 11:53:25 +053065
66Inorder to dereference the private data (in phy_ops), the phy provider driver
67can use phy_set_drvdata() after creating the PHY and use phy_get_drvdata() in
68phy_ops to get back the private data.
69
704. Getting a reference to the PHY
71
72Before the controller can make use of the PHY, it has to get a reference to
73it. This framework provides the following APIs to get a reference to the PHY.
74
75struct phy *phy_get(struct device *dev, const char *string);
Andrew Lunn788a4d52014-02-04 18:33:12 +010076struct phy *phy_optional_get(struct device *dev, const char *string);
Kishon Vijay Abraham Iff764962013-09-27 11:53:25 +053077struct phy *devm_phy_get(struct device *dev, const char *string);
Andrew Lunn788a4d52014-02-04 18:33:12 +010078struct phy *devm_phy_optional_get(struct device *dev, const char *string);
Arun Ramamurthy6be109b2015-04-22 16:04:11 -070079struct phy *devm_of_phy_get_by_index(struct device *dev, struct device_node *np,
80 int index);
Kishon Vijay Abraham Iff764962013-09-27 11:53:25 +053081
Andrew Lunn788a4d52014-02-04 18:33:12 +010082phy_get, phy_optional_get, devm_phy_get and devm_phy_optional_get can
83be used to get the PHY. In the case of dt boot, the string arguments
84should contain the phy name as given in the dt data and in the case of
85non-dt boot, it should contain the label of the PHY. The two
86devm_phy_get associates the device with the PHY using devres on
87successful PHY get. On driver detach, release function is invoked on
88the the devres data and devres data is freed. phy_optional_get and
89devm_phy_optional_get should be used when the phy is optional. These
90two functions will never return -ENODEV, but instead returns NULL when
Arun Ramamurthy6be109b2015-04-22 16:04:11 -070091the phy cannot be found.Some generic drivers, such as ehci, may use multiple
92phys and for such drivers referencing phy(s) by name(s) does not make sense. In
93this case, devm_of_phy_get_by_index can be used to get a phy reference based on
94the index.
Kishon Vijay Abraham Iff764962013-09-27 11:53:25 +053095
Andrew Lunn04c2fac2014-02-04 18:33:11 +010096It should be noted that NULL is a valid phy reference. All phy
97consumer calls on the NULL phy become NOPs. That is the release calls,
98the phy_init() and phy_exit() calls, and phy_power_on() and
99phy_power_off() calls are all NOP when applied to a NULL phy. The NULL
100phy is useful in devices for handling optional phy devices.
101
Kishon Vijay Abraham Iff764962013-09-27 11:53:25 +05301025. Releasing a reference to the PHY
103
104When the controller no longer needs the PHY, it has to release the reference
105to the PHY it has obtained using the APIs mentioned in the above section. The
106PHY framework provides 2 APIs to release a reference to the PHY.
107
108void phy_put(struct phy *phy);
109void devm_phy_put(struct device *dev, struct phy *phy);
110
111Both these APIs are used to release a reference to the PHY and devm_phy_put
112destroys the devres associated with this PHY.
113
1146. Destroying the PHY
115
116When the driver that created the PHY is unloaded, it should destroy the PHY it
117created using one of the following 2 APIs.
118
119void phy_destroy(struct phy *phy);
120void devm_phy_destroy(struct device *dev, struct phy *phy);
121
122Both these APIs destroy the PHY and devm_phy_destroy destroys the devres
123associated with this PHY.
124
1257. PM Runtime
126
127This subsystem is pm runtime enabled. So while creating the PHY,
128pm_runtime_enable of the phy device created by this subsystem is called and
129while destroying the PHY, pm_runtime_disable is called. Note that the phy
130device created by this subsystem will be a child of the device that calls
131phy_create (PHY provider device).
132
133So pm_runtime_get_sync of the phy_device created by this subsystem will invoke
134pm_runtime_get_sync of PHY provider device because of parent-child relationship.
135It should also be noted that phy_power_on and phy_power_off performs
136phy_pm_runtime_get_sync and phy_pm_runtime_put respectively.
137There are exported APIs like phy_pm_runtime_get, phy_pm_runtime_get_sync,
138phy_pm_runtime_put, phy_pm_runtime_put_sync, phy_pm_runtime_allow and
139phy_pm_runtime_forbid for performing PM operations.
140
Heikki Krogerusb7bc15b2014-11-19 17:28:18 +02001418. PHY Mappings
Kishon Vijay Abraham Iff764962013-09-27 11:53:25 +0530142
Heikki Krogerusb7bc15b2014-11-19 17:28:18 +0200143In order to get reference to a PHY without help from DeviceTree, the framework
144offers lookups which can be compared to clkdev that allow clk structures to be
145bound to devices. A lookup can be made be made during runtime when a handle to
146the struct phy already exists.
Kishon Vijay Abraham Iff764962013-09-27 11:53:25 +0530147
Heikki Krogerusb7bc15b2014-11-19 17:28:18 +0200148The framework offers the following API for registering and unregistering the
149lookups.
Kishon Vijay Abraham Iff764962013-09-27 11:53:25 +0530150
Heikki Krogerusb7bc15b2014-11-19 17:28:18 +0200151int phy_create_lookup(struct phy *phy, const char *con_id, const char *dev_id);
152void phy_remove_lookup(struct phy *phy, const char *con_id, const char *dev_id);
Kishon Vijay Abraham Iff764962013-09-27 11:53:25 +0530153
1549. DeviceTree Binding
155
156The documentation for PHY dt binding can be found @
157Documentation/devicetree/bindings/phy/phy-bindings.txt