1 ============= 1 =============
2 PHY subsystem 2 PHY subsystem
3 ============= 3 =============
4 4
5 :Author: Kishon Vijay Abraham I <kishon@ti.com> 5 :Author: Kishon Vijay Abraham I <kishon@ti.com>
6 6
7 This document explains the Generic PHY Framewo 7 This document explains the Generic PHY Framework along with the APIs provided,
8 and how-to-use. 8 and how-to-use.
9 9
10 Introduction 10 Introduction
11 ============ 11 ============
12 12
13 *PHY* is the abbreviation for physical layer. 13 *PHY* is the abbreviation for physical layer. It is used to connect a device
14 to the physical medium e.g., the USB controlle 14 to the physical medium e.g., the USB controller has a PHY to provide functions
15 such as serialization, de-serialization, encod 15 such as serialization, de-serialization, encoding, decoding and is responsible
16 for obtaining the required data transmission r 16 for obtaining the required data transmission rate. Note that some USB
17 controllers have PHY functionality embedded in 17 controllers have PHY functionality embedded into it and others use an external
18 PHY. Other peripherals that use PHY include Wi 18 PHY. Other peripherals that use PHY include Wireless LAN, Ethernet,
19 SATA etc. 19 SATA etc.
20 20
21 The intention of creating this framework is to 21 The intention of creating this framework is to bring the PHY drivers spread
22 all over the Linux kernel to drivers/phy to in 22 all over the Linux kernel to drivers/phy to increase code re-use and for
23 better code maintainability. 23 better code maintainability.
24 24
25 This framework will be of use only to devices 25 This framework will be of use only to devices that use external PHY (PHY
26 functionality is not embedded within the contr 26 functionality is not embedded within the controller).
27 27
28 Registering/Unregistering the PHY provider 28 Registering/Unregistering the PHY provider
29 ========================================== 29 ==========================================
30 30
31 PHY provider refers to an entity that implemen 31 PHY provider refers to an entity that implements one or more PHY instances.
32 For the simple case where the PHY provider imp 32 For the simple case where the PHY provider implements only a single instance of
33 the PHY, the framework provides its own implem 33 the PHY, the framework provides its own implementation of of_xlate in
34 of_phy_simple_xlate. If the PHY provider imple 34 of_phy_simple_xlate. If the PHY provider implements multiple instances, it
35 should provide its own implementation of of_xl 35 should provide its own implementation of of_xlate. of_xlate is used only for
36 dt boot case. 36 dt boot case.
37 37
38 :: 38 ::
39 39
40 #define of_phy_provider_register(dev, 40 #define of_phy_provider_register(dev, xlate) \
41 __of_phy_provider_register((de 41 __of_phy_provider_register((dev), NULL, THIS_MODULE, (xlate))
42 42
43 #define devm_of_phy_provider_register( 43 #define devm_of_phy_provider_register(dev, xlate) \
44 __devm_of_phy_provider_registe 44 __devm_of_phy_provider_register((dev), NULL, THIS_MODULE,
45 45 (xlate))
46 46
47 of_phy_provider_register and devm_of_phy_provi 47 of_phy_provider_register and devm_of_phy_provider_register macros can be used to
48 register the phy_provider and it takes device 48 register the phy_provider and it takes device and of_xlate as
49 arguments. For the dt boot case, all PHY provi 49 arguments. For the dt boot case, all PHY providers should use one of the above
50 2 macros to register the PHY provider. 50 2 macros to register the PHY provider.
51 51
52 Often the device tree nodes associated with a 52 Often the device tree nodes associated with a PHY provider will contain a set
53 of children that each represent a single PHY. 53 of children that each represent a single PHY. Some bindings may nest the child
54 nodes within extra levels for context and exte 54 nodes within extra levels for context and extensibility, in which case the low
55 level of_phy_provider_register_full() and devm 55 level of_phy_provider_register_full() and devm_of_phy_provider_register_full()
56 macros can be used to override the node contai 56 macros can be used to override the node containing the children.
57 57
58 :: 58 ::
59 59
60 #define of_phy_provider_register_full( 60 #define of_phy_provider_register_full(dev, children, xlate) \
61 __of_phy_provider_register(dev 61 __of_phy_provider_register(dev, children, THIS_MODULE, xlate)
62 62
63 #define devm_of_phy_provider_register_ 63 #define devm_of_phy_provider_register_full(dev, children, xlate) \
64 __devm_of_phy_provider_registe 64 __devm_of_phy_provider_register_full(dev, children,
65 65 THIS_MODULE, xlate)
66 66
67 void devm_of_phy_provider_unregister(s 67 void devm_of_phy_provider_unregister(struct device *dev,
68 struct phy_provider *phy_provi 68 struct phy_provider *phy_provider);
69 void of_phy_provider_unregister(struct 69 void of_phy_provider_unregister(struct phy_provider *phy_provider);
70 70
71 devm_of_phy_provider_unregister and of_phy_pro 71 devm_of_phy_provider_unregister and of_phy_provider_unregister can be used to
72 unregister the PHY. 72 unregister the PHY.
73 73
74 Creating the PHY 74 Creating the PHY
75 ================ 75 ================
76 76
77 The PHY driver should create the PHY in order 77 The PHY driver should create the PHY in order for other peripheral controllers
78 to make use of it. The PHY framework provides 78 to make use of it. The PHY framework provides 2 APIs to create the PHY.
79 79
80 :: 80 ::
81 81
82 struct phy *phy_create(struct device * 82 struct phy *phy_create(struct device *dev, struct device_node *node,
83 const struct ph 83 const struct phy_ops *ops);
84 struct phy *devm_phy_create(struct dev 84 struct phy *devm_phy_create(struct device *dev,
85 struct dev 85 struct device_node *node,
86 const stru 86 const struct phy_ops *ops);
87 87
88 The PHY drivers can use one of the above 2 API 88 The PHY drivers can use one of the above 2 APIs to create the PHY by passing
89 the device pointer and phy ops. 89 the device pointer and phy ops.
90 phy_ops is a set of function pointers for perf 90 phy_ops is a set of function pointers for performing PHY operations such as
91 init, exit, power_on and power_off. 91 init, exit, power_on and power_off.
92 92
93 Inorder to dereference the private data (in ph 93 Inorder to dereference the private data (in phy_ops), the phy provider driver
94 can use phy_set_drvdata() after creating the P 94 can use phy_set_drvdata() after creating the PHY and use phy_get_drvdata() in
95 phy_ops to get back the private data. 95 phy_ops to get back the private data.
96 96
97 Getting a reference to the PHY !! 97 4. Getting a reference to the PHY
98 ============================== <<
99 98
100 Before the controller can make use of the PHY, 99 Before the controller can make use of the PHY, it has to get a reference to
101 it. This framework provides the following APIs 100 it. This framework provides the following APIs to get a reference to the PHY.
102 101
103 :: 102 ::
104 103
105 struct phy *phy_get(struct device *dev 104 struct phy *phy_get(struct device *dev, const char *string);
>> 105 struct phy *phy_optional_get(struct device *dev, const char *string);
106 struct phy *devm_phy_get(struct device 106 struct phy *devm_phy_get(struct device *dev, const char *string);
107 struct phy *devm_phy_optional_get(stru 107 struct phy *devm_phy_optional_get(struct device *dev,
108 cons 108 const char *string);
109 struct phy *devm_of_phy_get(struct dev <<
110 const char <<
111 struct phy *devm_of_phy_optional_get(s <<
112 s <<
113 c <<
114 struct phy *devm_of_phy_get_by_index(s 109 struct phy *devm_of_phy_get_by_index(struct device *dev,
115 s 110 struct device_node *np,
116 i 111 int index);
117 112
118 phy_get, devm_phy_get and devm_phy_optional_ge !! 113 phy_get, phy_optional_get, devm_phy_get and devm_phy_optional_get can
119 In the case of dt boot, the string arguments !! 114 be used to get the PHY. In the case of dt boot, the string arguments
120 should contain the phy name as given in the dt 115 should contain the phy name as given in the dt data and in the case of
121 non-dt boot, it should contain the label of th 116 non-dt boot, it should contain the label of the PHY. The two
122 devm_phy_get associates the device with the PH 117 devm_phy_get associates the device with the PHY using devres on
123 successful PHY get. On driver detach, release 118 successful PHY get. On driver detach, release function is invoked on
124 the devres data and devres data is freed. !! 119 the devres data and devres data is freed. phy_optional_get and
125 The _optional_get variants should be used when !! 120 devm_phy_optional_get should be used when the phy is optional. These
126 functions will never return -ENODEV, but inste !! 121 two functions will never return -ENODEV, but instead returns NULL when
127 the phy cannot be found. !! 122 the phy cannot be found.Some generic drivers, such as ehci, may use multiple
128 Some generic drivers, such as ehci, may use mu !! 123 phys and for such drivers referencing phy(s) by name(s) does not make sense. In
129 devm_of_phy_get or devm_of_phy_get_by_index ca !! 124 this case, devm_of_phy_get_by_index can be used to get a phy reference based on
130 reference based on name or index. !! 125 the index.
131 126
132 It should be noted that NULL is a valid phy re 127 It should be noted that NULL is a valid phy reference. All phy
133 consumer calls on the NULL phy become NOPs. Th 128 consumer calls on the NULL phy become NOPs. That is the release calls,
134 the phy_init() and phy_exit() calls, and phy_p 129 the phy_init() and phy_exit() calls, and phy_power_on() and
135 phy_power_off() calls are all NOP when applied 130 phy_power_off() calls are all NOP when applied to a NULL phy. The NULL
136 phy is useful in devices for handling optional 131 phy is useful in devices for handling optional phy devices.
137 <<
138 Order of API calls <<
139 ================== <<
140 <<
141 The general order of calls should be:: <<
142 <<
143 [devm_][of_]phy_get() <<
144 phy_init() <<
145 phy_power_on() <<
146 [phy_set_mode[_ext]()] <<
147 ... <<
148 phy_power_off() <<
149 phy_exit() <<
150 [[of_]phy_put()] <<
151 <<
152 Some PHY drivers may not implement :c:func:`ph <<
153 but controllers should always call these funct <<
154 PHYs. Some PHYs may require :c:func:`phy_set_m <<
155 others may use a default mode (typically confi <<
156 firmware). For compatibility, you should alway <<
157 what mode you will be using. Generally, this f <<
158 :c:func:`phy_power_on`, although some PHY driv <<
159 132
160 Releasing a reference to the PHY 133 Releasing a reference to the PHY
161 ================================ 134 ================================
162 135
163 When the controller no longer needs the PHY, i 136 When the controller no longer needs the PHY, it has to release the reference
164 to the PHY it has obtained using the APIs ment 137 to the PHY it has obtained using the APIs mentioned in the above section. The
165 PHY framework provides 2 APIs to release a ref 138 PHY framework provides 2 APIs to release a reference to the PHY.
166 139
167 :: 140 ::
168 141
169 void phy_put(struct phy *phy); 142 void phy_put(struct phy *phy);
170 void devm_phy_put(struct device *dev, 143 void devm_phy_put(struct device *dev, struct phy *phy);
171 144
172 Both these APIs are used to release a referenc 145 Both these APIs are used to release a reference to the PHY and devm_phy_put
173 destroys the devres associated with this PHY. 146 destroys the devres associated with this PHY.
174 147
175 Destroying the PHY 148 Destroying the PHY
176 ================== 149 ==================
177 150
178 When the driver that created the PHY is unload 151 When the driver that created the PHY is unloaded, it should destroy the PHY it
179 created using one of the following 2 APIs:: 152 created using one of the following 2 APIs::
180 153
181 void phy_destroy(struct phy *phy); 154 void phy_destroy(struct phy *phy);
182 void devm_phy_destroy(struct device *d 155 void devm_phy_destroy(struct device *dev, struct phy *phy);
183 156
184 Both these APIs destroy the PHY and devm_phy_d 157 Both these APIs destroy the PHY and devm_phy_destroy destroys the devres
185 associated with this PHY. 158 associated with this PHY.
186 159
187 PM Runtime 160 PM Runtime
188 ========== 161 ==========
189 162
190 This subsystem is pm runtime enabled. So while 163 This subsystem is pm runtime enabled. So while creating the PHY,
191 pm_runtime_enable of the phy device created by 164 pm_runtime_enable of the phy device created by this subsystem is called and
192 while destroying the PHY, pm_runtime_disable i 165 while destroying the PHY, pm_runtime_disable is called. Note that the phy
193 device created by this subsystem will be a chi 166 device created by this subsystem will be a child of the device that calls
194 phy_create (PHY provider device). 167 phy_create (PHY provider device).
195 168
196 So pm_runtime_get_sync of the phy_device creat 169 So pm_runtime_get_sync of the phy_device created by this subsystem will invoke
197 pm_runtime_get_sync of PHY provider device bec 170 pm_runtime_get_sync of PHY provider device because of parent-child relationship.
198 It should also be noted that phy_power_on and 171 It should also be noted that phy_power_on and phy_power_off performs
199 phy_pm_runtime_get_sync and phy_pm_runtime_put 172 phy_pm_runtime_get_sync and phy_pm_runtime_put respectively.
200 There are exported APIs like phy_pm_runtime_ge 173 There are exported APIs like phy_pm_runtime_get, phy_pm_runtime_get_sync,
201 phy_pm_runtime_put, phy_pm_runtime_put_sync, p 174 phy_pm_runtime_put, phy_pm_runtime_put_sync, phy_pm_runtime_allow and
202 phy_pm_runtime_forbid for performing PM operat 175 phy_pm_runtime_forbid for performing PM operations.
203 176
204 PHY Mappings 177 PHY Mappings
205 ============ 178 ============
206 179
207 In order to get reference to a PHY without hel 180 In order to get reference to a PHY without help from DeviceTree, the framework
208 offers lookups which can be compared to clkdev 181 offers lookups which can be compared to clkdev that allow clk structures to be
209 bound to devices. A lookup can be made during 182 bound to devices. A lookup can be made during runtime when a handle to the
210 struct phy already exists. 183 struct phy already exists.
211 184
212 The framework offers the following API for reg 185 The framework offers the following API for registering and unregistering the
213 lookups:: 186 lookups::
214 187
215 int phy_create_lookup(struct phy *phy, 188 int phy_create_lookup(struct phy *phy, const char *con_id,
216 const char *dev_ 189 const char *dev_id);
217 void phy_remove_lookup(struct phy *phy 190 void phy_remove_lookup(struct phy *phy, const char *con_id,
218 const char *dev 191 const char *dev_id);
219 192
220 DeviceTree Binding 193 DeviceTree Binding
221 ================== 194 ==================
222 195
223 The documentation for PHY dt binding can be fo 196 The documentation for PHY dt binding can be found @
224 Documentation/devicetree/bindings/phy/phy-bind 197 Documentation/devicetree/bindings/phy/phy-bindings.txt
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