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Documentation: PCI: Tidy AER documentation

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Consistently use:

  PCIe          previously PCIe, PCI Express, or pci express
  Root Port     previously Root Port or root port
  Endpoint      previously EndPoint or endpoint
  AER           previously AER or aer
  please        previously pls

Also update a few awkward wordings.

Link: https://lore.kernel.org/r/20230609222500.1267795-5-helgaas@kernel.org
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
This commit is contained in:
Bjorn Helgaas 2023-06-09 17:25:00 -05:00
parent f142badf46
commit 11502feab4
1 changed files with 65 additions and 66 deletions
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131
Documentation/PCI/pcieaer-howto.rst
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@ -16,62 +16,61 @@ Overview
About this guide About this guide
---------------- ----------------
This guide describes the basics of the PCI Express Advanced Error This guide describes the basics of the PCI Express (PCIe) Advanced Error
Reporting (AER) driver and provides information on how to use it, as Reporting (AER) driver and provides information on how to use it, as
well as how to enable the drivers of endpoint devices to conform with well as how to enable the drivers of Endpoint devices to conform with
PCI Express AER driver. the PCIe AER driver.
What is the PCI Express AER Driver? What is the PCIe AER Driver?
----------------------------------- ----------------------------
PCI Express error signaling can occur on the PCI Express link itself PCIe error signaling can occur on the PCIe link itself
or on behalf of transactions initiated on the link. PCI Express or on behalf of transactions initiated on the link. PCIe
defines two error reporting paradigms: the baseline capability and defines two error reporting paradigms: the baseline capability and
the Advanced Error Reporting capability. The baseline capability is the Advanced Error Reporting capability. The baseline capability is
required of all PCI Express components providing a minimum defined required of all PCIe components providing a minimum defined
set of error reporting requirements. Advanced Error Reporting set of error reporting requirements. Advanced Error Reporting
capability is implemented with a PCI Express advanced error reporting capability is implemented with a PCIe Advanced Error Reporting
extended capability structure providing more robust error reporting. extended capability structure providing more robust error reporting.
The PCI Express AER driver provides the infrastructure to support PCI The PCIe AER driver provides the infrastructure to support PCIe Advanced
Express Advanced Error Reporting capability. The PCI Express AER Error Reporting capability. The PCIe AER driver provides three basic
driver provides three basic functions: functions:
- Gathers the comprehensive error information if errors occurred. - Gathers the comprehensive error information if errors occurred.
- Reports error to the users. - Reports error to the users.
- Performs error recovery actions. - Performs error recovery actions.
AER driver only attaches root ports which support PCI-Express AER The AER driver only attaches to Root Ports and RCECs that support the PCIe
capability. AER capability.
User Guide User Guide
========== ==========
Include the PCI Express AER Root Driver into the Linux Kernel Include the PCIe AER Root Driver into the Linux Kernel
------------------------------------------------------------- ------------------------------------------------------
The PCI Express AER Root driver is a Root Port service driver attached The PCIe AER driver is a Root Port service driver attached
to the PCI Express Port Bus driver. If a user wants to use it, the driver via the PCIe Port Bus driver. If a user wants to use it, the driver
has to be compiled. Option CONFIG_PCIEAER supports this capability. It must be compiled. It is enabled with CONFIG_PCIEAER, which
depends on CONFIG_PCIEPORTBUS, so pls. set CONFIG_PCIEPORTBUS=y and depends on CONFIG_PCIEPORTBUS.
CONFIG_PCIEAER = y.
Load PCI Express AER Root Driver Load PCIe AER Root Driver
-------------------------------- -------------------------
Some systems have AER support in firmware. Enabling Linux AER support at Some systems have AER support in firmware. Enabling Linux AER support at
the same time the firmware handles AER may result in unpredictable the same time the firmware handles AER would result in unpredictable
behavior. Therefore, Linux does not handle AER events unless the firmware behavior. Therefore, Linux does not handle AER events unless the firmware
grants AER control to the OS via the ACPI _OSC method. See the PCI FW 3.0 grants AER control to the OS via the ACPI _OSC method. See the PCI Firmware
Specification for details regarding _OSC usage. Specification for details regarding _OSC usage.
AER error output AER error output
---------------- ----------------
When a PCIe AER error is captured, an error message will be output to When a PCIe AER error is captured, an error message will be output to
console. If it's a correctable error, it is output as a warning. console. If it's a correctable error, it is output as an info message.
Otherwise, it is printed as an error. So users could choose different Otherwise, it is printed as an error. So users could choose different
log level to filter out correctable error messages. log level to filter out correctable error messages.
@ -82,9 +81,9 @@ Below shows an example::
0000:50:00.0: [20] Unsupported Request (First) 0000:50:00.0: [20] Unsupported Request (First)
0000:50:00.0: TLP Header: 04000001 00200a03 05010000 00050100 0000:50:00.0: TLP Header: 04000001 00200a03 05010000 00050100
In the example, 'Requester ID' means the ID of the device who sends In the example, 'Requester ID' means the ID of the device that sent
the error message to root port. Pls. refer to pci express specs for the error message to the Root Port. Please refer to PCIe specs for other
other fields. fields.
AER Statistics / Counters AER Statistics / Counters
------------------------- -------------------------
@ -96,41 +95,41 @@ Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
Developer Guide Developer Guide
=============== ===============
To enable AER aware support requires a software driver to provide To enable error recovery, a software driver must provide callbacks.
callbacks.
To support AER better, developers need understand how AER does work To support AER better, developers need to understand how AER works.
firstly.
PCI Express errors are classified into two types: correctable errors PCIe errors are classified into two types: correctable errors
and uncorrectable errors. This classification is based on the impacts and uncorrectable errors. This classification is based on the impact
of those errors, which may result in degraded performance or function of those errors, which may result in degraded performance or function
failure. failure.
Correctable errors pose no impacts on the functionality of the Correctable errors pose no impacts on the functionality of the
interface. The PCI Express protocol can recover without any software interface. The PCIe protocol can recover without any software
intervention or any loss of data. These errors are detected and intervention or any loss of data. These errors are detected and
corrected by hardware. Unlike correctable errors, uncorrectable corrected by hardware.
Unlike correctable errors, uncorrectable
errors impact functionality of the interface. Uncorrectable errors errors impact functionality of the interface. Uncorrectable errors
can cause a particular transaction or a particular PCI Express link can cause a particular transaction or a particular PCIe link
to be unreliable. Depending on those error conditions, uncorrectable to be unreliable. Depending on those error conditions, uncorrectable
errors are further classified into non-fatal errors and fatal errors. errors are further classified into non-fatal errors and fatal errors.
Non-fatal errors cause the particular transaction to be unreliable, Non-fatal errors cause the particular transaction to be unreliable,
but the PCI Express link itself is fully functional. Fatal errors, on but the PCIe link itself is fully functional. Fatal errors, on
the other hand, cause the link to be unreliable. the other hand, cause the link to be unreliable.
When AER is enabled, a PCI Express device will automatically send an When PCIe error reporting is enabled, a device will automatically send an
error message to the PCIe root port above it when the device captures error message to the Root Port above it when it captures
an error. The Root Port, upon receiving an error reporting message, an error. The Root Port, upon receiving an error reporting message,
internally processes and logs the error message in its PCI Express internally processes and logs the error message in its AER
capability structure. Error information being logged includes storing Capability structure. Error information being logged includes storing
the error reporting agent's requestor ID into the Error Source the error reporting agent's requestor ID into the Error Source
Identification Registers and setting the error bits of the Root Error Identification Registers and setting the error bits of the Root Error
Status Register accordingly. If AER error reporting is enabled in Root Status Register accordingly. If AER error reporting is enabled in the Root
Error Command Register, the Root Port generates an interrupt if an Error Command Register, the Root Port generates an interrupt when an
error is detected. error is detected.
Note that the errors as described above are related to the PCI Express Note that the errors as described above are related to the PCIe
hierarchy and links. These errors do not include any device specific hierarchy and links. These errors do not include any device specific
errors because device specific errors will still get sent directly to errors because device specific errors will still get sent directly to
the device driver. the device driver.
@ -138,14 +137,14 @@ the device driver.
Provide callbacks Provide callbacks
----------------- -----------------
callback reset_link to reset pci express link callback reset_link to reset PCIe link
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This callback is used to reset the pci express physical link when a This callback is used to reset the PCIe physical link when a
fatal error happens. The root port aer service driver provides a fatal error happens. The Root Port AER service driver provides a
default reset_link function, but different upstream ports might default reset_link function, but different Upstream Ports might
have different specifications to reset pci express link, so all have different specifications to reset the PCIe link, so
upstream ports should provide their own reset_link functions. Upstream Port drivers may provide their own reset_link functions.
Section 3.2.2.2 provides more detailed info on when to call Section 3.2.2.2 provides more detailed info on when to call
reset_link. reset_link.
@ -153,24 +152,24 @@ reset_link.
PCI error-recovery callbacks PCI error-recovery callbacks
~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The PCI Express AER Root driver uses error callbacks to coordinate The PCIe AER Root driver uses error callbacks to coordinate
with downstream device drivers associated with a hierarchy in question with downstream device drivers associated with a hierarchy in question
when performing error recovery actions. when performing error recovery actions.
Data struct pci_driver has a pointer, err_handler, to point to Data struct pci_driver has a pointer, err_handler, to point to
pci_error_handlers who consists of a couple of callback function pci_error_handlers who consists of a couple of callback function
pointers. AER driver follows the rules defined in pointers. The AER driver follows the rules defined in
pci-error-recovery.rst except pci express specific parts (e.g. pci-error-recovery.rst except PCIe-specific parts (e.g.
reset_link). Pls. refer to pci-error-recovery.rst for detailed reset_link). Please refer to pci-error-recovery.rst for detailed
definitions of the callbacks. definitions of the callbacks.
Below sections specify when to call the error callback functions. The sections below specify when to call the error callback functions.
Correctable errors Correctable errors
~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~
Correctable errors pose no impacts on the functionality of Correctable errors pose no impacts on the functionality of
the interface. The PCI Express protocol can recover without any the interface. The PCIe protocol can recover without any
software intervention or any loss of data. These errors do not software intervention or any loss of data. These errors do not
require any recovery actions. The AER driver clears the device's require any recovery actions. The AER driver clears the device's
correctable error status register accordingly and logs these errors. correctable error status register accordingly and logs these errors.
@ -181,12 +180,12 @@ Non-correctable (non-fatal and fatal) errors
If an error message indicates a non-fatal error, performing link reset If an error message indicates a non-fatal error, performing link reset
at upstream is not required. The AER driver calls error_detected(dev, at upstream is not required. The AER driver calls error_detected(dev,
pci_channel_io_normal) to all drivers associated within a hierarchy in pci_channel_io_normal) to all drivers associated within a hierarchy in
question. for example:: question. For example::
EndPoint<==>DownstreamPort B<==>UpstreamPort A<==>RootPort Endpoint <==> Downstream Port B <==> Upstream Port A <==> Root Port
If Upstream port A captures an AER error, the hierarchy consists of If Upstream Port A captures an AER error, the hierarchy consists of
Downstream port B and EndPoint. Downstream Port B and Endpoint.
A driver may return PCI_ERS_RESULT_CAN_RECOVER, A driver may return PCI_ERS_RESULT_CAN_RECOVER,
PCI_ERS_RESULT_DISCONNECT, or PCI_ERS_RESULT_NEED_RESET, depending on PCI_ERS_RESULT_DISCONNECT, or PCI_ERS_RESULT_NEED_RESET, depending on
@ -207,7 +206,7 @@ Frequent Asked Questions
------------------------ ------------------------
Q: Q:
What happens if a PCI Express device driver does not provide an What happens if a PCIe device driver does not provide an
error recovery handler (pci_driver->err_handler is equal to NULL)? error recovery handler (pci_driver->err_handler is equal to NULL)?
A: A:
@ -244,5 +243,5 @@ from:
https://git.kernel.org/cgit/linux/kernel/git/gong.chen/aer-inject.git/ https://git.kernel.org/cgit/linux/kernel/git/gong.chen/aer-inject.git/
More information about aer-inject can be found in the document comes More information about aer-inject can be found in the document in
with its source code. its source code.