1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 ============================= 3 =============================
4 ACPI Based Device Enumeration 4 ACPI Based Device Enumeration
5 ============================= 5 =============================
6 6
7 ACPI 5 introduced a set of new resources (Uart 7 ACPI 5 introduced a set of new resources (UartTSerialBus, I2cSerialBus,
8 SpiSerialBus, GpioIo and GpioInt) which can be 8 SpiSerialBus, GpioIo and GpioInt) which can be used in enumerating slave
9 devices behind serial bus controllers. 9 devices behind serial bus controllers.
10 10
11 In addition we are starting to see peripherals 11 In addition we are starting to see peripherals integrated in the
12 SoC/Chipset to appear only in ACPI namespace. 12 SoC/Chipset to appear only in ACPI namespace. These are typically devices
13 that are accessed through memory-mapped regist 13 that are accessed through memory-mapped registers.
14 14
15 In order to support this and re-use the existi 15 In order to support this and re-use the existing drivers as much as
16 possible we decided to do following: 16 possible we decided to do following:
17 17
18 - Devices that have no bus connector resourc 18 - Devices that have no bus connector resource are represented as
19 platform devices. 19 platform devices.
20 20
21 - Devices behind real busses where there is 21 - Devices behind real busses where there is a connector resource
22 are represented as struct spi_device or st !! 22 are represented as struct spi_device or struct i2c_device
23 that standard UARTs are not busses so ther !! 23 (standard UARTs are not busses so there is no struct uart_device).
24 although some of them may be represented b <<
25 24
26 As both ACPI and Device Tree represent a tree 25 As both ACPI and Device Tree represent a tree of devices (and their
27 resources) this implementation follows the Dev 26 resources) this implementation follows the Device Tree way as much as
28 possible. 27 possible.
29 28
30 The ACPI implementation enumerates devices beh !! 29 The ACPI implementation enumerates devices behind busses (platform, SPI and
31 I2C, and in some cases UART), creates the phys !! 30 I2C), creates the physical devices and binds them to their ACPI handle in
32 to their ACPI handle in the ACPI namespace. !! 31 the ACPI namespace.
33 32
34 This means that when ACPI_HANDLE(dev) returns 33 This means that when ACPI_HANDLE(dev) returns non-NULL the device was
35 enumerated from ACPI namespace. This handle ca 34 enumerated from ACPI namespace. This handle can be used to extract other
36 device-specific configuration. There is an exa 35 device-specific configuration. There is an example of this below.
37 36
38 Platform bus support 37 Platform bus support
39 ==================== 38 ====================
40 39
41 Since we are using platform devices to represe 40 Since we are using platform devices to represent devices that are not
42 connected to any physical bus we only need to 41 connected to any physical bus we only need to implement a platform driver
43 for the device and add supported ACPI IDs. If 42 for the device and add supported ACPI IDs. If this same IP-block is used on
44 some other non-ACPI platform, the driver might 43 some other non-ACPI platform, the driver might work out of the box or needs
45 some minor changes. 44 some minor changes.
46 45
47 Adding ACPI support for an existing driver sho 46 Adding ACPI support for an existing driver should be pretty
48 straightforward. Here is the simplest example: 47 straightforward. Here is the simplest example::
49 48
>> 49 #ifdef CONFIG_ACPI
50 static const struct acpi_device_id myd 50 static const struct acpi_device_id mydrv_acpi_match[] = {
51 /* ACPI IDs here */ 51 /* ACPI IDs here */
52 { } 52 { }
53 }; 53 };
54 MODULE_DEVICE_TABLE(acpi, mydrv_acpi_m 54 MODULE_DEVICE_TABLE(acpi, mydrv_acpi_match);
>> 55 #endif
55 56
56 static struct platform_driver my_drive 57 static struct platform_driver my_driver = {
57 ... 58 ...
58 .driver = { 59 .driver = {
59 .acpi_match_table = my !! 60 .acpi_match_table = ACPI_PTR(mydrv_acpi_match),
60 }, 61 },
61 }; 62 };
62 63
63 If the driver needs to perform more complex in 64 If the driver needs to perform more complex initialization like getting and
64 configuring GPIOs it can get its ACPI handle a 65 configuring GPIOs it can get its ACPI handle and extract this information
65 from ACPI tables. 66 from ACPI tables.
66 67
67 ACPI device objects <<
68 =================== <<
69 <<
70 Generally speaking, there are two categories o <<
71 ACPI is used as an interface between the platf <<
72 that can be discovered and enumerated natively <<
73 the specific bus that they are on (for example <<
74 without the platform firmware assistance, and <<
75 by the platform firmware so that they can be d <<
76 known to the platform firmware, regardless of <<
77 there can be a corresponding ACPI device objec <<
78 case the Linux kernel will create a struct acp <<
79 that device. <<
80 <<
81 Those struct acpi_device objects are never use <<
82 discoverable devices, because they are represe <<
83 objects (for example, struct pci_dev for PCI d <<
84 device drivers (the corresponding struct acpi_ <<
85 an additional source of information on the con <<
86 Moreover, the core ACPI device enumeration cod <<
87 objects for the majority of devices that are d <<
88 help of the platform firmware and those platfo <<
89 by platform drivers in direct analogy with the <<
90 case. Therefore it is logically inconsistent <<
91 drivers to struct acpi_device objects, includi <<
92 discovered with the help of the platform firmw <<
93 <<
94 Historically, ACPI drivers that bound directly <<
95 were implemented for some devices enumerated w <<
96 firmware, but this is not recommended for any <<
97 platform device objects are created for those <<
98 exceptions that are not relevant here) and so <<
99 for handling them, even though the correspondi <<
100 only source of device configuration informatio <<
101 <<
102 For every device having a corresponding struct <<
103 to it is returned by the ACPI_COMPANION() macr <<
104 get to the device configuration information st <<
105 this way. Accordingly, struct acpi_device can <<
106 interface between the kernel and the ACPI Name <<
107 other types (for example, struct pci_dev or st <<
108 for interacting with the rest of the system. <<
109 <<
110 DMA support 68 DMA support
111 =========== 69 ===========
112 70
113 DMA controllers enumerated via ACPI should be 71 DMA controllers enumerated via ACPI should be registered in the system to
114 provide generic access to their resources. For 72 provide generic access to their resources. For example, a driver that would
115 like to be accessible to slave devices via gen 73 like to be accessible to slave devices via generic API call
116 dma_request_chan() must register itself at the 74 dma_request_chan() must register itself at the end of the probe function like
117 this:: 75 this::
118 76
119 err = devm_acpi_dma_controller_registe 77 err = devm_acpi_dma_controller_register(dev, xlate_func, dw);
120 /* Handle the error if it's not a case 78 /* Handle the error if it's not a case of !CONFIG_ACPI */
121 79
122 and implement custom xlate function if needed 80 and implement custom xlate function if needed (usually acpi_dma_simple_xlate()
123 is enough) which converts the FixedDMA resourc 81 is enough) which converts the FixedDMA resource provided by struct
124 acpi_dma_spec into the corresponding DMA chann 82 acpi_dma_spec into the corresponding DMA channel. A piece of code for that case
125 could look like:: 83 could look like::
126 84
127 #ifdef CONFIG_ACPI 85 #ifdef CONFIG_ACPI
128 struct filter_args { 86 struct filter_args {
129 /* Provide necessary informati 87 /* Provide necessary information for the filter_func */
130 ... 88 ...
131 }; 89 };
132 90
133 static bool filter_func(struct dma_cha 91 static bool filter_func(struct dma_chan *chan, void *param)
134 { 92 {
135 /* Choose the proper channel * 93 /* Choose the proper channel */
136 ... 94 ...
137 } 95 }
138 96
139 static struct dma_chan *xlate_func(str 97 static struct dma_chan *xlate_func(struct acpi_dma_spec *dma_spec,
140 struct acpi_dma *adma) 98 struct acpi_dma *adma)
141 { 99 {
142 dma_cap_mask_t cap; 100 dma_cap_mask_t cap;
143 struct filter_args args; 101 struct filter_args args;
144 102
145 /* Prepare arguments for filte 103 /* Prepare arguments for filter_func */
146 ... 104 ...
147 return dma_request_channel(cap 105 return dma_request_channel(cap, filter_func, &args);
148 } 106 }
149 #else 107 #else
150 static struct dma_chan *xlate_func(str 108 static struct dma_chan *xlate_func(struct acpi_dma_spec *dma_spec,
151 struct acpi_dma *adma) 109 struct acpi_dma *adma)
152 { 110 {
153 return NULL; 111 return NULL;
154 } 112 }
155 #endif 113 #endif
156 114
157 dma_request_chan() will call xlate_func() for 115 dma_request_chan() will call xlate_func() for each registered DMA controller.
158 In the xlate function the proper channel must 116 In the xlate function the proper channel must be chosen based on
159 information in struct acpi_dma_spec and the pr 117 information in struct acpi_dma_spec and the properties of the controller
160 provided by struct acpi_dma. 118 provided by struct acpi_dma.
161 119
162 Clients must call dma_request_chan() with the 120 Clients must call dma_request_chan() with the string parameter that corresponds
163 to a specific FixedDMA resource. By default "t 121 to a specific FixedDMA resource. By default "tx" means the first entry of the
164 FixedDMA resource array, "rx" means the second 122 FixedDMA resource array, "rx" means the second entry. The table below shows a
165 layout:: 123 layout::
166 124
167 Device (I2C0) 125 Device (I2C0)
168 { 126 {
169 ... 127 ...
170 Method (_CRS, 0, NotSerialized 128 Method (_CRS, 0, NotSerialized)
171 { 129 {
172 Name (DBUF, ResourceTe 130 Name (DBUF, ResourceTemplate ()
173 { 131 {
174 FixedDMA (0x00 132 FixedDMA (0x0018, 0x0004, Width32bit, _Y48)
175 FixedDMA (0x00 133 FixedDMA (0x0019, 0x0005, Width32bit, )
176 }) 134 })
177 ... 135 ...
178 } 136 }
179 } 137 }
180 138
181 So, the FixedDMA with request line 0x0018 is " 139 So, the FixedDMA with request line 0x0018 is "tx" and next one is "rx" in
182 this example. 140 this example.
183 141
184 In robust cases the client unfortunately needs 142 In robust cases the client unfortunately needs to call
185 acpi_dma_request_slave_chan_by_index() directl 143 acpi_dma_request_slave_chan_by_index() directly and therefore choose the
186 specific FixedDMA resource by its index. 144 specific FixedDMA resource by its index.
187 145
188 Named Interrupts <<
189 ================ <<
190 <<
191 Drivers enumerated via ACPI can have names to <<
192 which can be used to get the IRQ number in the <<
193 <<
194 The interrupt name can be listed in _DSD as 'i <<
195 should be listed as an array of strings which <<
196 resource in the ACPI table corresponding to it <<
197 <<
198 The table below shows an example of its usage: <<
199 <<
200 Device (DEV0) { <<
201 ... <<
202 Name (_CRS, ResourceTemplate() { <<
203 ... <<
204 Interrupt (ResourceConsumer, Level <<
205 0x20, <<
206 0x24 <<
207 } <<
208 }) <<
209 <<
210 Name (_DSD, Package () { <<
211 ToUUID("daffd814-6eba-4d8c-8a91-bc <<
212 Package () { <<
213 Package () { "interrupt-names" <<
214 } <<
215 ... <<
216 }) <<
217 } <<
218 <<
219 The interrupt name 'default' will correspond t <<
220 resource and 'alert' to 0x24. Note that only t <<
221 is mapped and not GpioInt() or similar. <<
222 <<
223 The driver can call the function - fwnode_irq_ <<
224 and interrupt name as arguments to get the cor <<
225 <<
226 SPI serial bus support 146 SPI serial bus support
227 ====================== 147 ======================
228 148
229 Slave devices behind SPI bus have SpiSerialBus 149 Slave devices behind SPI bus have SpiSerialBus resource attached to them.
230 This is extracted automatically by the SPI cor 150 This is extracted automatically by the SPI core and the slave devices are
231 enumerated once spi_register_master() is calle 151 enumerated once spi_register_master() is called by the bus driver.
232 152
233 Here is what the ACPI namespace for a SPI slav 153 Here is what the ACPI namespace for a SPI slave might look like::
234 154
235 Device (EEP0) 155 Device (EEP0)
236 { 156 {
237 Name (_ADR, 1) 157 Name (_ADR, 1)
238 Name (_CID, Package () { !! 158 Name (_CID, Package() {
239 "ATML0025", 159 "ATML0025",
240 "AT25", 160 "AT25",
241 }) 161 })
242 ... 162 ...
243 Method (_CRS, 0, NotSerialized 163 Method (_CRS, 0, NotSerialized)
244 { 164 {
245 SPISerialBus(1, Polari 165 SPISerialBus(1, PolarityLow, FourWireMode, 8,
246 ControllerInit 166 ControllerInitiated, 1000000, ClockPolarityLow,
247 ClockPhaseFirs 167 ClockPhaseFirst, "\\_SB.PCI0.SPI1",)
248 } 168 }
249 ... 169 ...
250 170
251 The SPI device drivers only need to add ACPI I !! 171 The SPI device drivers only need to add ACPI IDs in a similar way than with
252 the platform device drivers. Below is an examp 172 the platform device drivers. Below is an example where we add ACPI support
253 to at25 SPI eeprom driver (this is meant for t 173 to at25 SPI eeprom driver (this is meant for the above ACPI snippet)::
254 174
>> 175 #ifdef CONFIG_ACPI
255 static const struct acpi_device_id at2 176 static const struct acpi_device_id at25_acpi_match[] = {
256 { "AT25", 0 }, 177 { "AT25", 0 },
257 { } !! 178 { },
258 }; 179 };
259 MODULE_DEVICE_TABLE(acpi, at25_acpi_ma 180 MODULE_DEVICE_TABLE(acpi, at25_acpi_match);
>> 181 #endif
260 182
261 static struct spi_driver at25_driver = 183 static struct spi_driver at25_driver = {
262 .driver = { 184 .driver = {
263 ... 185 ...
264 .acpi_match_table = at !! 186 .acpi_match_table = ACPI_PTR(at25_acpi_match),
265 }, 187 },
266 }; 188 };
267 189
268 Note that this driver actually needs more info 190 Note that this driver actually needs more information like page size of the
269 eeprom, etc. This information can be passed vi !! 191 eeprom etc. but at the time writing this there is no standard way of
>> 192 passing those. One idea is to return this in _DSM method like::
270 193
271 Device (EEP0) 194 Device (EEP0)
272 { 195 {
273 ... 196 ...
274 Name (_DSD, Package () !! 197 Method (_DSM, 4, NotSerialized)
275 { 198 {
276 ToUUID("daffd814-6eba- !! 199 Store (Package (6)
277 Package () <<
278 { 200 {
279 Package () { " !! 201 "byte-len", 1024,
280 Package () { " !! 202 "addr-mode", 2,
281 Package () { " !! 203 "page-size, 32
282 } !! 204 }, Local0)
283 }) !! 205
284 } !! 206 // Check UUIDs etc.
>> 207
>> 208 Return (Local0)
>> 209 }
285 210
286 Then the at25 SPI driver can get this configur !! 211 Then the at25 SPI driver can get this configuration by calling _DSM on its
287 APIs during ->probe() phase like:: !! 212 ACPI handle like::
288 213
289 err = device_property_read_u32(dev, "s !! 214 struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
290 if (err) !! 215 struct acpi_object_list input;
291 ...error handling... !! 216 acpi_status status;
292 !! 217
293 err = device_property_read_u32(dev, "p !! 218 /* Fill in the input buffer */
294 if (err) !! 219
295 ...error handling... !! 220 status = acpi_evaluate_object(ACPI_HANDLE(&spi->dev), "_DSM",
296 !! 221 &input, &output);
297 err = device_property_read_u32(dev, "a !! 222 if (ACPI_FAILURE(status))
298 if (err) !! 223 /* Handle the error */
299 ...error handling... !! 224
>> 225 /* Extract the data here */
>> 226
>> 227 kfree(output.pointer);
300 228
301 I2C serial bus support 229 I2C serial bus support
302 ====================== 230 ======================
303 231
304 The slaves behind I2C bus controller only need 232 The slaves behind I2C bus controller only need to add the ACPI IDs like
305 with the platform and SPI drivers. The I2C cor 233 with the platform and SPI drivers. The I2C core automatically enumerates
306 any slave devices behind the controller device 234 any slave devices behind the controller device once the adapter is
307 registered. 235 registered.
308 236
309 Below is an example of how to add ACPI support 237 Below is an example of how to add ACPI support to the existing mpu3050
310 input driver:: 238 input driver::
311 239
>> 240 #ifdef CONFIG_ACPI
312 static const struct acpi_device_id mpu 241 static const struct acpi_device_id mpu3050_acpi_match[] = {
313 { "MPU3050", 0 }, 242 { "MPU3050", 0 },
314 { } !! 243 { },
315 }; 244 };
316 MODULE_DEVICE_TABLE(acpi, mpu3050_acpi 245 MODULE_DEVICE_TABLE(acpi, mpu3050_acpi_match);
>> 246 #endif
317 247
318 static struct i2c_driver mpu3050_i2c_d 248 static struct i2c_driver mpu3050_i2c_driver = {
319 .driver = { 249 .driver = {
320 .name = "mpu3050", 250 .name = "mpu3050",
>> 251 .owner = THIS_MODULE,
321 .pm = &mpu3050_pm, 252 .pm = &mpu3050_pm,
322 .of_match_table = mpu3 253 .of_match_table = mpu3050_of_match,
323 .acpi_match_table = mp !! 254 .acpi_match_table = ACPI_PTR(mpu3050_acpi_match),
324 }, 255 },
325 .probe = mpu3050_prob 256 .probe = mpu3050_probe,
326 .remove = mpu3050_remo 257 .remove = mpu3050_remove,
327 .id_table = mpu3050_ids, 258 .id_table = mpu3050_ids,
328 }; 259 };
329 module_i2c_driver(mpu3050_i2c_driver); <<
330 260
331 Reference to PWM device 261 Reference to PWM device
332 ======================= 262 =======================
333 263
334 Sometimes a device can be a consumer of PWM ch 264 Sometimes a device can be a consumer of PWM channel. Obviously OS would like
335 to know which one. To provide this mapping the 265 to know which one. To provide this mapping the special property has been
336 introduced, i.e.:: 266 introduced, i.e.::
337 267
338 Device (DEV) 268 Device (DEV)
339 { 269 {
340 Name (_DSD, Package () 270 Name (_DSD, Package ()
341 { 271 {
342 ToUUID("daffd814-6eba-4d8c-8a91-bc 272 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
343 Package () { 273 Package () {
344 Package () { "compatible", Pac 274 Package () { "compatible", Package () { "pwm-leds" } },
345 Package () { "label", "alarm-l 275 Package () { "label", "alarm-led" },
346 Package () { "pwms", 276 Package () { "pwms",
347 Package () { 277 Package () {
348 "\\_SB.PCI0.PWM", // 278 "\\_SB.PCI0.PWM", // <PWM device reference>
349 0, // 279 0, // <PWM index>
350 600000000, // 280 600000000, // <PWM period>
351 0, // 281 0, // <PWM flags>
352 } 282 }
353 } 283 }
354 } 284 }
>> 285
355 }) 286 })
356 ... 287 ...
357 } <<
358 288
359 In the above example the PWM-based LED driver 289 In the above example the PWM-based LED driver references to the PWM channel 0
360 of \_SB.PCI0.PWM device with initial period se 290 of \_SB.PCI0.PWM device with initial period setting equal to 600 ms (note that
361 value is given in nanoseconds). 291 value is given in nanoseconds).
362 292
363 GPIO support 293 GPIO support
364 ============ 294 ============
365 295
366 ACPI 5 introduced two new resources to describ 296 ACPI 5 introduced two new resources to describe GPIO connections: GpioIo
367 and GpioInt. These resources can be used to pa 297 and GpioInt. These resources can be used to pass GPIO numbers used by
368 the device to the driver. ACPI 5.1 extended th 298 the device to the driver. ACPI 5.1 extended this with _DSD (Device
369 Specific Data) which made it possible to name 299 Specific Data) which made it possible to name the GPIOs among other things.
370 300
371 For example:: 301 For example::
372 302
373 Device (DEV) 303 Device (DEV)
374 { 304 {
375 Method (_CRS, 0, NotSerialized 305 Method (_CRS, 0, NotSerialized)
376 { 306 {
377 Name (SBUF, ResourceTe 307 Name (SBUF, ResourceTemplate()
378 { 308 {
>> 309 ...
379 // Used to pow 310 // Used to power on/off the device
380 GpioIo (Exclus !! 311 GpioIo (Exclusive, PullDefault, 0x0000, 0x0000,
381 "\\_SB !! 312 IoRestrictionOutputOnly, "\\_SB.PCI0.GPI0",
>> 313 0x00, ResourceConsumer,,)
>> 314 {
>> 315 // Pin List
>> 316 0x0055
>> 317 }
382 318
383 // Interrupt f 319 // Interrupt for the device
384 GpioInt (Edge, !! 320 GpioInt (Edge, ActiveHigh, ExclusiveAndWake, PullNone,
385 "\\_S !! 321 0x0000, "\\_SB.PCI0.GPI0", 0x00, ResourceConsumer,,)
>> 322 {
>> 323 // Pin list
>> 324 0x0058
>> 325 }
>> 326
>> 327 ...
>> 328
386 } 329 }
387 330
388 Return (SBUF) 331 Return (SBUF)
389 } 332 }
390 333
391 // ACPI 5.1 _DSD used for nami 334 // ACPI 5.1 _DSD used for naming the GPIOs
392 Name (_DSD, Package () 335 Name (_DSD, Package ()
393 { 336 {
394 ToUUID("daffd814-6eba- 337 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
395 Package () 338 Package ()
396 { 339 {
397 Package () { " !! 340 Package () {"power-gpios", Package() {^DEV, 0, 0, 0 }},
398 Package () { " !! 341 Package () {"irq-gpios", Package() {^DEV, 1, 0, 0 }},
399 } 342 }
400 }) 343 })
401 ... 344 ...
402 } <<
403 345
404 These GPIO numbers are controller relative and 346 These GPIO numbers are controller relative and path "\\_SB.PCI0.GPI0"
405 specifies the path to the controller. In order 347 specifies the path to the controller. In order to use these GPIOs in Linux
406 we need to translate them to the corresponding 348 we need to translate them to the corresponding Linux GPIO descriptors.
407 349
408 There is a standard GPIO API for that and it i !! 350 There is a standard GPIO API for that and is documented in
409 Documentation/admin-guide/gpio/. 351 Documentation/admin-guide/gpio/.
410 352
411 In the above example we can get the correspond 353 In the above example we can get the corresponding two GPIO descriptors with
412 a code like this:: 354 a code like this::
413 355
414 #include <linux/gpio/consumer.h> 356 #include <linux/gpio/consumer.h>
415 ... 357 ...
416 358
417 struct gpio_desc *irq_desc, *power_des 359 struct gpio_desc *irq_desc, *power_desc;
418 360
419 irq_desc = gpiod_get(dev, "irq"); 361 irq_desc = gpiod_get(dev, "irq");
420 if (IS_ERR(irq_desc)) 362 if (IS_ERR(irq_desc))
421 /* handle error */ 363 /* handle error */
422 364
423 power_desc = gpiod_get(dev, "power"); 365 power_desc = gpiod_get(dev, "power");
424 if (IS_ERR(power_desc)) 366 if (IS_ERR(power_desc))
425 /* handle error */ 367 /* handle error */
426 368
427 /* Now we can use the GPIO descriptors 369 /* Now we can use the GPIO descriptors */
428 370
429 There are also devm_* versions of these functi 371 There are also devm_* versions of these functions which release the
430 descriptors once the device is released. 372 descriptors once the device is released.
431 373
432 See Documentation/firmware-guide/acpi/gpio-pro 374 See Documentation/firmware-guide/acpi/gpio-properties.rst for more information
433 about the _DSD binding related to GPIOs. 375 about the _DSD binding related to GPIOs.
434 376
435 RS-485 support <<
436 ============== <<
437 <<
438 ACPI _DSD (Device Specific Data) can be used t <<
439 of UART. <<
440 <<
441 For example:: <<
442 <<
443 Device (DEV) <<
444 { <<
445 ... <<
446 <<
447 // ACPI 5.1 _DSD used for RS-4 <<
448 Name (_DSD, Package () <<
449 { <<
450 ToUUID("daffd814-6eba- <<
451 Package () <<
452 { <<
453 Package () {"r <<
454 Package () {"r <<
455 Package () {"r <<
456 } <<
457 }) <<
458 ... <<
459 <<
460 MFD devices 377 MFD devices
461 =========== 378 ===========
462 379
463 The MFD devices register their children as pla 380 The MFD devices register their children as platform devices. For the child
464 devices there needs to be an ACPI handle that 381 devices there needs to be an ACPI handle that they can use to reference
465 parts of the ACPI namespace that relate to the 382 parts of the ACPI namespace that relate to them. In the Linux MFD subsystem
466 we provide two ways: 383 we provide two ways:
467 384
468 - The children share the parent ACPI handle. 385 - The children share the parent ACPI handle.
469 - The MFD cell can specify the ACPI id of th 386 - The MFD cell can specify the ACPI id of the device.
470 387
471 For the first case, the MFD drivers do not nee 388 For the first case, the MFD drivers do not need to do anything. The
472 resulting child platform device will have its 389 resulting child platform device will have its ACPI_COMPANION() set to point
473 to the parent device. 390 to the parent device.
474 391
475 If the ACPI namespace has a device that we can 392 If the ACPI namespace has a device that we can match using an ACPI id or ACPI
476 adr, the cell should be set like:: 393 adr, the cell should be set like::
477 394
478 static struct mfd_cell_acpi_match my_s 395 static struct mfd_cell_acpi_match my_subdevice_cell_acpi_match = {
479 .pnpid = "XYZ0001", 396 .pnpid = "XYZ0001",
480 .adr = 0, 397 .adr = 0,
481 }; 398 };
482 399
483 static struct mfd_cell my_subdevice_ce 400 static struct mfd_cell my_subdevice_cell = {
484 .name = "my_subdevice", 401 .name = "my_subdevice",
485 /* set the resources relative 402 /* set the resources relative to the parent */
486 .acpi_match = &my_subdevice_ce 403 .acpi_match = &my_subdevice_cell_acpi_match,
487 }; 404 };
488 405
489 The ACPI id "XYZ0001" is then used to lookup a 406 The ACPI id "XYZ0001" is then used to lookup an ACPI device directly under
490 the MFD device and if found, that ACPI compani 407 the MFD device and if found, that ACPI companion device is bound to the
491 resulting child platform device. 408 resulting child platform device.
492 409
493 Device Tree namespace link device ID 410 Device Tree namespace link device ID
494 ==================================== 411 ====================================
495 412
496 The Device Tree protocol uses device identific 413 The Device Tree protocol uses device identification based on the "compatible"
497 property whose value is a string or an array o 414 property whose value is a string or an array of strings recognized as device
498 identifiers by drivers and the driver core. T 415 identifiers by drivers and the driver core. The set of all those strings may be
499 regarded as a device identification namespace 416 regarded as a device identification namespace analogous to the ACPI/PNP device
500 ID namespace. Consequently, in principle it s 417 ID namespace. Consequently, in principle it should not be necessary to allocate
501 a new (and arguably redundant) ACPI/PNP device 418 a new (and arguably redundant) ACPI/PNP device ID for a devices with an existing
502 identification string in the Device Tree (DT) 419 identification string in the Device Tree (DT) namespace, especially if that ID
503 is only needed to indicate that a given device 420 is only needed to indicate that a given device is compatible with another one,
504 presumably having a matching driver in the ker 421 presumably having a matching driver in the kernel already.
505 422
506 In ACPI, the device identification object call 423 In ACPI, the device identification object called _CID (Compatible ID) is used to
507 list the IDs of devices the given one is compa 424 list the IDs of devices the given one is compatible with, but those IDs must
508 belong to one of the namespaces prescribed by 425 belong to one of the namespaces prescribed by the ACPI specification (see
509 Section 6.1.2 of ACPI 6.0 for details) and the 426 Section 6.1.2 of ACPI 6.0 for details) and the DT namespace is not one of them.
510 Moreover, the specification mandates that eith 427 Moreover, the specification mandates that either a _HID or an _ADR identification
511 object be present for all ACPI objects represe 428 object be present for all ACPI objects representing devices (Section 6.1 of ACPI
512 6.0). For non-enumerable bus types that objec 429 6.0). For non-enumerable bus types that object must be _HID and its value must
513 be a device ID from one of the namespaces pres 430 be a device ID from one of the namespaces prescribed by the specification too.
514 431
515 The special DT namespace link device ID, PRP00 432 The special DT namespace link device ID, PRP0001, provides a means to use the
516 existing DT-compatible device identification i 433 existing DT-compatible device identification in ACPI and to satisfy the above
517 requirements following from the ACPI specifica 434 requirements following from the ACPI specification at the same time. Namely,
518 if PRP0001 is returned by _HID, the ACPI subsy 435 if PRP0001 is returned by _HID, the ACPI subsystem will look for the
519 "compatible" property in the device object's _ 436 "compatible" property in the device object's _DSD and will use the value of that
520 property to identify the corresponding device 437 property to identify the corresponding device in analogy with the original DT
521 device identification algorithm. If the "comp 438 device identification algorithm. If the "compatible" property is not present
522 or its value is not valid, the device will not 439 or its value is not valid, the device will not be enumerated by the ACPI
523 subsystem. Otherwise, it will be enumerated a 440 subsystem. Otherwise, it will be enumerated automatically as a platform device
524 (except when an I2C or SPI link from the devic 441 (except when an I2C or SPI link from the device to its parent is present, in
525 which case the ACPI core will leave the device 442 which case the ACPI core will leave the device enumeration to the parent's
526 driver) and the identification strings from th 443 driver) and the identification strings from the "compatible" property value will
527 be used to find a driver for the device along 444 be used to find a driver for the device along with the device IDs listed by _CID
528 (if present). 445 (if present).
529 446
530 Analogously, if PRP0001 is present in the list 447 Analogously, if PRP0001 is present in the list of device IDs returned by _CID,
531 the identification strings listed by the "comp 448 the identification strings listed by the "compatible" property value (if present
532 and valid) will be used to look for a driver m 449 and valid) will be used to look for a driver matching the device, but in that
533 case their relative priority with respect to t 450 case their relative priority with respect to the other device IDs listed by
534 _HID and _CID depends on the position of PRP00 451 _HID and _CID depends on the position of PRP0001 in the _CID return package.
535 Specifically, the device IDs returned by _HID 452 Specifically, the device IDs returned by _HID and preceding PRP0001 in the _CID
536 return package will be checked first. Also in 453 return package will be checked first. Also in that case the bus type the device
537 will be enumerated to depends on the device ID 454 will be enumerated to depends on the device ID returned by _HID.
538 455
539 For example, the following ACPI sample might b 456 For example, the following ACPI sample might be used to enumerate an lm75-type
540 I2C temperature sensor and match it to the dri 457 I2C temperature sensor and match it to the driver using the Device Tree
541 namespace link:: 458 namespace link::
542 459
543 Device (TMP0) 460 Device (TMP0)
544 { 461 {
545 Name (_HID, "PRP0001") 462 Name (_HID, "PRP0001")
546 Name (_DSD, Package () { !! 463 Name (_DSD, Package() {
547 ToUUID("daffd814-6eba- 464 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
548 Package () { 465 Package () {
549 Package () { " !! 466 Package (2) { "compatible", "ti,tmp75" },
550 } 467 }
551 }) 468 })
552 Method (_CRS, 0, Serialized) 469 Method (_CRS, 0, Serialized)
553 { 470 {
554 Name (SBUF, ResourceTe 471 Name (SBUF, ResourceTemplate ()
555 { 472 {
556 I2cSerialBusV2 473 I2cSerialBusV2 (0x48, ControllerInitiated,
557 400000 474 400000, AddressingMode7Bit,
558 "\\_SB 475 "\\_SB.PCI0.I2C1", 0x00,
559 Resour 476 ResourceConsumer, , Exclusive,)
560 }) 477 })
561 Return (SBUF) 478 Return (SBUF)
562 } 479 }
563 } 480 }
564 481
565 It is valid to define device objects with a _H 482 It is valid to define device objects with a _HID returning PRP0001 and without
566 the "compatible" property in the _DSD or a _CI 483 the "compatible" property in the _DSD or a _CID as long as one of their
567 ancestors provides a _DSD with a valid "compat 484 ancestors provides a _DSD with a valid "compatible" property. Such device
568 objects are then simply regarded as additional 485 objects are then simply regarded as additional "blocks" providing hierarchical
569 configuration information to the driver of the 486 configuration information to the driver of the composite ancestor device.
570 487
571 However, PRP0001 can only be returned from eit 488 However, PRP0001 can only be returned from either _HID or _CID of a device
572 object if all of the properties returned by th 489 object if all of the properties returned by the _DSD associated with it (either
573 the _DSD of the device object itself or the _D 490 the _DSD of the device object itself or the _DSD of its ancestor in the
574 "composite device" case described above) can b 491 "composite device" case described above) can be used in the ACPI environment.
575 Otherwise, the _DSD itself is regarded as inva 492 Otherwise, the _DSD itself is regarded as invalid and therefore the "compatible"
576 property returned by it is meaningless. 493 property returned by it is meaningless.
577 494
578 Refer to Documentation/firmware-guide/acpi/DSD 495 Refer to Documentation/firmware-guide/acpi/DSD-properties-rules.rst for more
579 information. 496 information.
580 497
581 PCI hierarchy representation 498 PCI hierarchy representation
582 ============================ 499 ============================
583 500
584 Sometimes it could be useful to enumerate a PC !! 501 Sometimes could be useful to enumerate a PCI device, knowing its position on the
585 the PCI bus. !! 502 PCI bus.
586 503
587 For example, some systems use PCI devices sold 504 For example, some systems use PCI devices soldered directly on the mother board,
588 in a fixed position (ethernet, Wi-Fi, serial p 505 in a fixed position (ethernet, Wi-Fi, serial ports, etc.). In this conditions it
589 is possible to refer to these PCI devices know 506 is possible to refer to these PCI devices knowing their position on the PCI bus
590 topology. 507 topology.
591 508
592 To identify a PCI device, a complete hierarchi 509 To identify a PCI device, a complete hierarchical description is required, from
593 the chipset root port to the final device, thr 510 the chipset root port to the final device, through all the intermediate
594 bridges/switches of the board. 511 bridges/switches of the board.
595 512
596 For example, let's assume we have a system wit !! 513 For example, let us assume to have a system with a PCIe serial port, an
597 Exar XR17V3521, soldered on the main board. Th 514 Exar XR17V3521, soldered on the main board. This UART chip also includes
598 16 GPIOs and we want to add the property ``gpi !! 515 16 GPIOs and we want to add the property ``gpio-line-names`` [1] to these pins.
599 In this case, the ``lspci`` output for this co 516 In this case, the ``lspci`` output for this component is::
600 517
601 07:00.0 Serial controller: Exar Corp. 518 07:00.0 Serial controller: Exar Corp. XR17V3521 Dual PCIe UART (rev 03)
602 519
603 The complete ``lspci`` output (manually reduce 520 The complete ``lspci`` output (manually reduced in length) is::
604 521
605 00:00.0 Host bridge: Intel Corp... Hos 522 00:00.0 Host bridge: Intel Corp... Host Bridge (rev 0d)
606 ... 523 ...
607 00:13.0 PCI bridge: Intel Corp... PCI 524 00:13.0 PCI bridge: Intel Corp... PCI Express Port A #1 (rev fd)
608 00:13.1 PCI bridge: Intel Corp... PCI 525 00:13.1 PCI bridge: Intel Corp... PCI Express Port A #2 (rev fd)
609 00:13.2 PCI bridge: Intel Corp... PCI 526 00:13.2 PCI bridge: Intel Corp... PCI Express Port A #3 (rev fd)
610 00:14.0 PCI bridge: Intel Corp... PCI 527 00:14.0 PCI bridge: Intel Corp... PCI Express Port B #1 (rev fd)
611 00:14.1 PCI bridge: Intel Corp... PCI 528 00:14.1 PCI bridge: Intel Corp... PCI Express Port B #2 (rev fd)
612 ... 529 ...
613 05:00.0 PCI bridge: Pericom Semiconduc 530 05:00.0 PCI bridge: Pericom Semiconductor Device 2404 (rev 05)
614 06:01.0 PCI bridge: Pericom Semiconduc 531 06:01.0 PCI bridge: Pericom Semiconductor Device 2404 (rev 05)
615 06:02.0 PCI bridge: Pericom Semiconduc 532 06:02.0 PCI bridge: Pericom Semiconductor Device 2404 (rev 05)
616 06:03.0 PCI bridge: Pericom Semiconduc 533 06:03.0 PCI bridge: Pericom Semiconductor Device 2404 (rev 05)
617 07:00.0 Serial controller: Exar Corp. 534 07:00.0 Serial controller: Exar Corp. XR17V3521 Dual PCIe UART (rev 03) <-- Exar
618 ... 535 ...
619 536
620 The bus topology is:: 537 The bus topology is::
621 538
622 -[0000:00]-+-00.0 539 -[0000:00]-+-00.0
623 ... 540 ...
624 +-13.0-[01]----00.0 541 +-13.0-[01]----00.0
625 +-13.1-[02]----00.0 542 +-13.1-[02]----00.0
626 +-13.2-[03]-- 543 +-13.2-[03]--
627 +-14.0-[04]----00.0 544 +-14.0-[04]----00.0
628 +-14.1-[05-09]----00.0-[06- 545 +-14.1-[05-09]----00.0-[06-09]--+-01.0-[07]----00.0 <-- Exar
629 | 546 | +-02.0-[08]----00.0
630 | 547 | \-03.0-[09]--
631 ... 548 ...
632 \-1f.1 549 \-1f.1
633 550
634 To describe this Exar device on the PCI bus, w 551 To describe this Exar device on the PCI bus, we must start from the ACPI name
635 of the chipset bridge (also called "root port" 552 of the chipset bridge (also called "root port") with address::
636 553
637 Bus: 0 - Device: 14 - Function: 1 554 Bus: 0 - Device: 14 - Function: 1
638 555
639 To find this information, it is necessary to d !! 556 To find this information is necessary disassemble the BIOS ACPI tables, in
640 in particular the DSDT (see also [2]_):: !! 557 particular the DSDT (see also [2])::
641 558
642 mkdir ~/tables/ 559 mkdir ~/tables/
643 cd ~/tables/ 560 cd ~/tables/
644 acpidump > acpidump 561 acpidump > acpidump
645 acpixtract -a acpidump 562 acpixtract -a acpidump
646 iasl -e ssdt?.* -d dsdt.dat 563 iasl -e ssdt?.* -d dsdt.dat
647 564
648 Now, in the dsdt.dsl, we have to search the de 565 Now, in the dsdt.dsl, we have to search the device whose address is related to
649 0x14 (device) and 0x01 (function). In this cas 566 0x14 (device) and 0x01 (function). In this case we can find the following
650 device:: 567 device::
651 568
652 Scope (_SB.PCI0) 569 Scope (_SB.PCI0)
653 { 570 {
654 ... other definitions follow ... 571 ... other definitions follow ...
655 Device (RP02) 572 Device (RP02)
656 { 573 {
657 Method (_ADR, 0, NotSe 574 Method (_ADR, 0, NotSerialized) // _ADR: Address
658 { 575 {
659 If ((RPA2 != Z 576 If ((RPA2 != Zero))
660 { 577 {
661 Return 578 Return (RPA2) /* \RPA2 */
662 } 579 }
663 Else 580 Else
664 { 581 {
665 Return 582 Return (0x00140001)
666 } 583 }
667 } 584 }
668 ... other definitions follow ... 585 ... other definitions follow ...
669 586
670 and the _ADR method [3]_ returns exactly the d !! 587 and the _ADR method [3] returns exactly the device/function couple that
671 we are looking for. With this information and 588 we are looking for. With this information and analyzing the above ``lspci``
672 output (both the devices list and the devices 589 output (both the devices list and the devices tree), we can write the following
673 ACPI description for the Exar PCIe UART, also 590 ACPI description for the Exar PCIe UART, also adding the list of its GPIO line
674 names:: 591 names::
675 592
676 Scope (_SB.PCI0.RP02) 593 Scope (_SB.PCI0.RP02)
677 { 594 {
678 Device (BRG1) //Bridge 595 Device (BRG1) //Bridge
679 { 596 {
680 Name (_ADR, 0x0000) 597 Name (_ADR, 0x0000)
681 598
682 Device (BRG2) //Bridge 599 Device (BRG2) //Bridge
683 { 600 {
684 Name (_ADR, 0x 601 Name (_ADR, 0x00010000)
685 602
686 Device (EXAR) 603 Device (EXAR)
687 { 604 {
688 Name ( 605 Name (_ADR, 0x0000)
689 606
690 Name ( 607 Name (_DSD, Package ()
691 { 608 {
692 609 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
693 610 Package ()
694 611 {
695 612 Package ()
696 613 {
697 614 "gpio-line-names",
698 615 Package ()
699 616 {
700 617 "mode_232",
701 618 "mode_422",
702 619 "mode_485",
703 620 "misc_1",
704 621 "misc_2",
705 622 "misc_3",
706 623 "",
707 624 "",
708 625 "aux_1",
709 626 "aux_2",
710 627 "aux_3",
711 628 }
712 629 }
713 630 }
714 }) 631 })
715 } 632 }
716 } 633 }
717 } 634 }
718 } 635 }
719 636
720 The location "_SB.PCI0.RP02" is obtained by th 637 The location "_SB.PCI0.RP02" is obtained by the above investigation in the
721 dsdt.dsl table, whereas the device names "BRG1 638 dsdt.dsl table, whereas the device names "BRG1", "BRG2" and "EXAR" are
722 created analyzing the position of the Exar UAR 639 created analyzing the position of the Exar UART in the PCI bus topology.
723 640
724 References 641 References
725 ========== 642 ==========
726 643
727 .. [1] Documentation/firmware-guide/acpi/gpio- !! 644 [1] Documentation/firmware-guide/acpi/gpio-properties.rst
728 645
729 .. [2] Documentation/admin-guide/acpi/initrd_t !! 646 [2] Documentation/admin-guide/acpi/initrd_table_override.rst
730 647
731 .. [3] ACPI Specifications, Version 6.3 - Para !! 648 [3] ACPI Specifications, Version 6.3 - Paragraph 6.1.1 _ADR Address)
732 https://uefi.org/sites/default/files/resou 649 https://uefi.org/sites/default/files/resources/ACPI_6_3_May16.pdf,
733 referenced 2020-11-18 650 referenced 2020-11-18
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