diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/firmware-guide/acpi/dsd/leds.rst | 8 | ||||
| -rw-r--r-- | Documentation/firmware-guide/acpi/enumeration.rst | 154 | ||||
| -rw-r--r-- | Documentation/firmware-guide/acpi/gpio-properties.rst | 56 |
3 files changed, 213 insertions, 5 deletions
diff --git a/Documentation/firmware-guide/acpi/dsd/leds.rst b/Documentation/firmware-guide/acpi/dsd/leds.rst index aba1e9abfeeb..b99fff8e06f2 100644 --- a/Documentation/firmware-guide/acpi/dsd/leds.rst +++ b/Documentation/firmware-guide/acpi/dsd/leds.rst @@ -90,10 +90,10 @@ where References ========== -[1] Device tree. <URL:https://www.devicetree.org>, referenced 2019-02-21. +[1] Device tree. https://www.devicetree.org, referenced 2019-02-21. [2] Advanced Configuration and Power Interface Specification. - <URL:https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf>, + https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf, referenced 2019-02-21. [3] Documentation/devicetree/bindings/leds/common.txt @@ -101,11 +101,11 @@ References [4] Documentation/devicetree/bindings/media/video-interfaces.txt [5] Device Properties UUID For _DSD. - <URL:https://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf>, + https://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf, referenced 2019-02-21. [6] Hierarchical Data Extension UUID For _DSD. - <URL:https://www.uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.1.pdf>, + https://www.uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.1.pdf, referenced 2019-02-21. [7] Documentation/firmware-guide/acpi/dsd/data-node-references.rst diff --git a/Documentation/firmware-guide/acpi/enumeration.rst b/Documentation/firmware-guide/acpi/enumeration.rst index c13fee8b02ba..9f0d5c854fa4 100644 --- a/Documentation/firmware-guide/acpi/enumeration.rst +++ b/Documentation/firmware-guide/acpi/enumeration.rst @@ -461,3 +461,157 @@ Otherwise, the _DSD itself is regarded as invalid and therefore the "compatible" property returned by it is meaningless. Refer to :doc:`DSD-properties-rules` for more information. + +PCI hierarchy representation +============================ + +Sometimes could be useful to enumerate a PCI device, knowing its position on the +PCI bus. + +For example, some systems use PCI devices soldered directly on the mother board, +in a fixed position (ethernet, Wi-Fi, serial ports, etc.). In this conditions it +is possible to refer to these PCI devices knowing their position on the PCI bus +topology. + +To identify a PCI device, a complete hierarchical description is required, from +the chipset root port to the final device, through all the intermediate +bridges/switches of the board. + +For example, let us assume to have a system with a PCIe serial port, an +Exar XR17V3521, soldered on the main board. This UART chip also includes +16 GPIOs and we want to add the property ``gpio-line-names`` [1] to these pins. +In this case, the ``lspci`` output for this component is:: + + 07:00.0 Serial controller: Exar Corp. XR17V3521 Dual PCIe UART (rev 03) + +The complete ``lspci`` output (manually reduced in length) is:: + + 00:00.0 Host bridge: Intel Corp... Host Bridge (rev 0d) + ... + 00:13.0 PCI bridge: Intel Corp... PCI Express Port A #1 (rev fd) + 00:13.1 PCI bridge: Intel Corp... PCI Express Port A #2 (rev fd) + 00:13.2 PCI bridge: Intel Corp... PCI Express Port A #3 (rev fd) + 00:14.0 PCI bridge: Intel Corp... PCI Express Port B #1 (rev fd) + 00:14.1 PCI bridge: Intel Corp... PCI Express Port B #2 (rev fd) + ... + 05:00.0 PCI bridge: Pericom Semiconductor Device 2404 (rev 05) + 06:01.0 PCI bridge: Pericom Semiconductor Device 2404 (rev 05) + 06:02.0 PCI bridge: Pericom Semiconductor Device 2404 (rev 05) + 06:03.0 PCI bridge: Pericom Semiconductor Device 2404 (rev 05) + 07:00.0 Serial controller: Exar Corp. XR17V3521 Dual PCIe UART (rev 03) <-- Exar + ... + +The bus topology is:: + + -[0000:00]-+-00.0 + ... + +-13.0-[01]----00.0 + +-13.1-[02]----00.0 + +-13.2-[03]-- + +-14.0-[04]----00.0 + +-14.1-[05-09]----00.0-[06-09]--+-01.0-[07]----00.0 <-- Exar + | +-02.0-[08]----00.0 + | \-03.0-[09]-- + ... + \-1f.1 + +To describe this Exar device on the PCI bus, we must start from the ACPI name +of the chipset bridge (also called "root port") with address:: + + Bus: 0 - Device: 14 - Function: 1 + +To find this information is necessary disassemble the BIOS ACPI tables, in +particular the DSDT (see also [2]):: + + mkdir ~/tables/ + cd ~/tables/ + acpidump > acpidump + acpixtract -a acpidump + iasl -e ssdt?.* -d dsdt.dat + +Now, in the dsdt.dsl, we have to search the device whose address is related to +0x14 (device) and 0x01 (function). In this case we can find the following +device:: + + Scope (_SB.PCI0) + { + ... other definitions follow ... + Device (RP02) + { + Method (_ADR, 0, NotSerialized) // _ADR: Address + { + If ((RPA2 != Zero)) + { + Return (RPA2) /* \RPA2 */ + } + Else + { + Return (0x00140001) + } + } + ... other definitions follow ... + +and the _ADR method [3] returns exactly the device/function couple that +we are looking for. With this information and analyzing the above ``lspci`` +output (both the devices list and the devices tree), we can write the following +ACPI description for the Exar PCIe UART, also adding the list of its GPIO line +names:: + + Scope (_SB.PCI0.RP02) + { + Device (BRG1) //Bridge + { + Name (_ADR, 0x0000) + + Device (BRG2) //Bridge + { + Name (_ADR, 0x00010000) + + Device (EXAR) + { + Name (_ADR, 0x0000) + + Name (_DSD, Package () + { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + Package () + { + Package () + { + "gpio-line-names", + Package () + { + "mode_232", + "mode_422", + "mode_485", + "misc_1", + "misc_2", + "misc_3", + "", + "", + "aux_1", + "aux_2", + "aux_3", + } + } + } + }) + } + } + } + } + +The location "_SB.PCI0.RP02" is obtained by the above investigation in the +dsdt.dsl table, whereas the device names "BRG1", "BRG2" and "EXAR" are +created analyzing the position of the Exar UART in the PCI bus topology. + +References +========== + +[1] Documentation/firmware-guide/acpi/gpio-properties.rst + +[2] Documentation/admin-guide/acpi/initrd_table_override.rst + +[3] ACPI Specifications, Version 6.3 - Paragraph 6.1.1 _ADR Address) + https://uefi.org/sites/default/files/resources/ACPI_6_3_May16.pdf, + referenced 2020-11-18 diff --git a/Documentation/firmware-guide/acpi/gpio-properties.rst b/Documentation/firmware-guide/acpi/gpio-properties.rst index 59aad6138b6e..b36aa3e743d8 100644 --- a/Documentation/firmware-guide/acpi/gpio-properties.rst +++ b/Documentation/firmware-guide/acpi/gpio-properties.rst @@ -133,7 +133,61 @@ Example:: - gpio-line-names -Example:: +The ``gpio-line-names`` declaration is a list of strings ("names"), which +describes each line/pin of a GPIO controller/expander. This list, contained in +a package, must be inserted inside the GPIO controller declaration of an ACPI +table (typically inside the DSDT). The ``gpio-line-names`` list must respect the +following rules (see also the examples): + + - the first name in the list corresponds with the first line/pin of the GPIO + controller/expander + - the names inside the list must be consecutive (no "holes" are permitted) + - the list can be incomplete and can end before the last GPIO line: in + other words, it is not mandatory to fill all the GPIO lines + - empty names are allowed (two quotation marks ``""`` correspond to an empty + name) + +Example of a GPIO controller of 16 lines, with an incomplete list with two +empty names:: + + Package () { + "gpio-line-names", + Package () { + "pin_0", + "pin_1", + "", + "", + "pin_3", + "pin_4_push_button", + } + } + +At runtime, the above declaration produces the following result (using the +"libgpiod" tools):: + + root@debian:~# gpioinfo gpiochip4 + gpiochip4 - 16 lines: + line 0: "pin_0" unused input active-high + line 1: "pin_1" unused input active-high + line 2: unnamed unused input active-high + line 3: unnamed unused input active-high + line 4: "pin_3" unused input active-high + line 5: "pin_4_push_button" unused input active-high + line 6: unnamed unused input active-high + line 7 unnamed unused input active-high + line 8: unnamed unused input active-high + line 9: unnamed unused input active-high + line 10: unnamed unused input active-high + line 11: unnamed unused input active-high + line 12: unnamed unused input active-high + line 13: unnamed unused input active-high + line 14: unnamed unused input active-high + line 15: unnamed unused input active-high + root@debian:~# gpiofind pin_4_push_button + gpiochip4 5 + root@debian:~# + +Another example:: Package () { "gpio-line-names", |