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Documentation: PCI: convert pci-error-recovery.txt to reST
Convert plain text documentation to reStructuredText format and add it to Sphinx TOC tree. No essential content change. Signed-off-by: Changbin Du <changbin.du@gmail.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
This commit is contained in:
Changbin Du
Bjorn Helgaas
parent
b66357f32f
commit
8a01fa6434
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@ -13,3 +13,4 @@ Linux PCI Bus Subsystem
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pci-iov-howto
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msi-howto
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acpi-info
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pci-error-recovery
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@ -1,12 +1,13 @@
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.. SPDX-License-Identifier: GPL-2.0
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PCI Error Recovery
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------------------
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February 2, 2006
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==================
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PCI Error Recovery
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==================
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Current document maintainer:
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Linas Vepstas <linasvepstas@gmail.com>
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updated by Richard Lary <rlary@us.ibm.com>
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and Mike Mason <mmlnx@us.ibm.com> on 27-Jul-2009
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:Authors: - Linas Vepstas <linasvepstas@gmail.com>
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- Richard Lary <rlary@us.ibm.com>
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- Mike Mason <mmlnx@us.ibm.com>
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Many PCI bus controllers are able to detect a variety of hardware
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@ -63,7 +64,8 @@ mechanisms for dealing with SCSI bus errors and SCSI bus resets.
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Detailed Design
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---------------
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===============
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Design and implementation details below, based on a chain of
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public email discussions with Ben Herrenschmidt, circa 5 April 2005.
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@ -73,30 +75,33 @@ pci_driver. A driver that fails to provide the structure is "non-aware",
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and the actual recovery steps taken are platform dependent. The
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arch/powerpc implementation will simulate a PCI hotplug remove/add.
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This structure has the form:
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struct pci_error_handlers
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{
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int (*error_detected)(struct pci_dev *dev, enum pci_channel_state);
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int (*mmio_enabled)(struct pci_dev *dev);
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int (*slot_reset)(struct pci_dev *dev);
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void (*resume)(struct pci_dev *dev);
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};
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This structure has the form::
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The possible channel states are:
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enum pci_channel_state {
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pci_channel_io_normal, /* I/O channel is in normal state */
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pci_channel_io_frozen, /* I/O to channel is blocked */
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pci_channel_io_perm_failure, /* PCI card is dead */
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};
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struct pci_error_handlers
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{
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int (*error_detected)(struct pci_dev *dev, enum pci_channel_state);
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int (*mmio_enabled)(struct pci_dev *dev);
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int (*slot_reset)(struct pci_dev *dev);
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void (*resume)(struct pci_dev *dev);
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};
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Possible return values are:
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enum pci_ers_result {
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PCI_ERS_RESULT_NONE, /* no result/none/not supported in device driver */
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PCI_ERS_RESULT_CAN_RECOVER, /* Device driver can recover without slot reset */
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PCI_ERS_RESULT_NEED_RESET, /* Device driver wants slot to be reset. */
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PCI_ERS_RESULT_DISCONNECT, /* Device has completely failed, is unrecoverable */
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PCI_ERS_RESULT_RECOVERED, /* Device driver is fully recovered and operational */
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};
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The possible channel states are::
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enum pci_channel_state {
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pci_channel_io_normal, /* I/O channel is in normal state */
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pci_channel_io_frozen, /* I/O to channel is blocked */
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pci_channel_io_perm_failure, /* PCI card is dead */
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};
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Possible return values are::
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enum pci_ers_result {
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PCI_ERS_RESULT_NONE, /* no result/none/not supported in device driver */
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PCI_ERS_RESULT_CAN_RECOVER, /* Device driver can recover without slot reset */
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PCI_ERS_RESULT_NEED_RESET, /* Device driver wants slot to be reset. */
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PCI_ERS_RESULT_DISCONNECT, /* Device has completely failed, is unrecoverable */
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PCI_ERS_RESULT_RECOVERED, /* Device driver is fully recovered and operational */
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};
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A driver does not have to implement all of these callbacks; however,
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if it implements any, it must implement error_detected(). If a callback
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@ -134,16 +139,17 @@ shouldn't do any new IOs. Called in task context. This is sort of a
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All drivers participating in this system must implement this call.
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The driver must return one of the following result codes:
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- PCI_ERS_RESULT_CAN_RECOVER:
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Driver returns this if it thinks it might be able to recover
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the HW by just banging IOs or if it wants to be given
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a chance to extract some diagnostic information (see
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mmio_enable, below).
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- PCI_ERS_RESULT_NEED_RESET:
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Driver returns this if it can't recover without a
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slot reset.
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- PCI_ERS_RESULT_DISCONNECT:
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Driver returns this if it doesn't want to recover at all.
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- PCI_ERS_RESULT_CAN_RECOVER
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Driver returns this if it thinks it might be able to recover
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the HW by just banging IOs or if it wants to be given
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a chance to extract some diagnostic information (see
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mmio_enable, below).
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- PCI_ERS_RESULT_NEED_RESET
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Driver returns this if it can't recover without a
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slot reset.
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- PCI_ERS_RESULT_DISCONNECT
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Driver returns this if it doesn't want to recover at all.
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The next step taken will depend on the result codes returned by the
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drivers.
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@ -159,25 +165,27 @@ then recovery proceeds to STEP 4 (Slot Reset).
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If the platform is unable to recover the slot, the next step
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is STEP 6 (Permanent Failure).
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>>> The current powerpc implementation assumes that a device driver will
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>>> *not* schedule or semaphore in this routine; the current powerpc
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>>> implementation uses one kernel thread to notify all devices;
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>>> thus, if one device sleeps/schedules, all devices are affected.
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>>> Doing better requires complex multi-threaded logic in the error
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>>> recovery implementation (e.g. waiting for all notification threads
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>>> to "join" before proceeding with recovery.) This seems excessively
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>>> complex and not worth implementing.
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.. note::
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>>> The current powerpc implementation doesn't much care if the device
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>>> attempts I/O at this point, or not. I/O's will fail, returning
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>>> a value of 0xff on read, and writes will be dropped. If more than
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>>> EEH_MAX_FAILS I/O's are attempted to a frozen adapter, EEH
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>>> assumes that the device driver has gone into an infinite loop
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>>> and prints an error to syslog. A reboot is then required to
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>>> get the device working again.
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The current powerpc implementation assumes that a device driver will
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*not* schedule or semaphore in this routine; the current powerpc
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implementation uses one kernel thread to notify all devices;
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thus, if one device sleeps/schedules, all devices are affected.
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Doing better requires complex multi-threaded logic in the error
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recovery implementation (e.g. waiting for all notification threads
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to "join" before proceeding with recovery.) This seems excessively
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complex and not worth implementing.
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The current powerpc implementation doesn't much care if the device
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attempts I/O at this point, or not. I/O's will fail, returning
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a value of 0xff on read, and writes will be dropped. If more than
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EEH_MAX_FAILS I/O's are attempted to a frozen adapter, EEH
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assumes that the device driver has gone into an infinite loop
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and prints an error to syslog. A reboot is then required to
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get the device working again.
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STEP 2: MMIO Enabled
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-------------------
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--------------------
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The platform re-enables MMIO to the device (but typically not the
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DMA), and then calls the mmio_enabled() callback on all affected
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device drivers.
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@ -192,34 +200,36 @@ link reset was performed by the HW. If the platform can't just re-enable IOs
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without a slot reset or a link reset, it will not call this callback, and
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instead will have gone directly to STEP 3 (Link Reset) or STEP 4 (Slot Reset)
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>>> The following is proposed; no platform implements this yet:
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>>> Proposal: All I/O's should be done _synchronously_ from within
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>>> this callback, errors triggered by them will be returned via
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>>> the normal pci_check_whatever() API, no new error_detected()
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>>> callback will be issued due to an error happening here. However,
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>>> such an error might cause IOs to be re-blocked for the whole
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>>> segment, and thus invalidate the recovery that other devices
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>>> on the same segment might have done, forcing the whole segment
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>>> into one of the next states, that is, link reset or slot reset.
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.. note::
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The following is proposed; no platform implements this yet:
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Proposal: All I/O's should be done _synchronously_ from within
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this callback, errors triggered by them will be returned via
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the normal pci_check_whatever() API, no new error_detected()
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callback will be issued due to an error happening here. However,
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such an error might cause IOs to be re-blocked for the whole
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segment, and thus invalidate the recovery that other devices
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on the same segment might have done, forcing the whole segment
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into one of the next states, that is, link reset or slot reset.
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The driver should return one of the following result codes:
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- PCI_ERS_RESULT_RECOVERED
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Driver returns this if it thinks the device is fully
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functional and thinks it is ready to start
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normal driver operations again. There is no
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guarantee that the driver will actually be
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allowed to proceed, as another driver on the
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same segment might have failed and thus triggered a
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slot reset on platforms that support it.
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- PCI_ERS_RESULT_RECOVERED
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Driver returns this if it thinks the device is fully
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functional and thinks it is ready to start
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normal driver operations again. There is no
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guarantee that the driver will actually be
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allowed to proceed, as another driver on the
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same segment might have failed and thus triggered a
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slot reset on platforms that support it.
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- PCI_ERS_RESULT_NEED_RESET
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Driver returns this if it thinks the device is not
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recoverable in its current state and it needs a slot
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reset to proceed.
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- PCI_ERS_RESULT_NEED_RESET
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Driver returns this if it thinks the device is not
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recoverable in its current state and it needs a slot
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reset to proceed.
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- PCI_ERS_RESULT_DISCONNECT
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Same as above. Total failure, no recovery even after
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reset driver dead. (To be defined more precisely)
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- PCI_ERS_RESULT_DISCONNECT
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Same as above. Total failure, no recovery even after
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reset driver dead. (To be defined more precisely)
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The next step taken depends on the results returned by the drivers.
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If all drivers returned PCI_ERS_RESULT_RECOVERED, then the platform
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@ -293,31 +303,33 @@ device will be considered "dead" in this case.
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Drivers for multi-function cards will need to coordinate among
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themselves as to which driver instance will perform any "one-shot"
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or global device initialization. For example, the Symbios sym53cxx2
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driver performs device init only from PCI function 0:
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driver performs device init only from PCI function 0::
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+ if (PCI_FUNC(pdev->devfn) == 0)
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+ sym_reset_scsi_bus(np, 0);
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+ if (PCI_FUNC(pdev->devfn) == 0)
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+ sym_reset_scsi_bus(np, 0);
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Result codes:
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- PCI_ERS_RESULT_DISCONNECT
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Same as above.
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Result codes:
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- PCI_ERS_RESULT_DISCONNECT
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Same as above.
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Drivers for PCI Express cards that require a fundamental reset must
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set the needs_freset bit in the pci_dev structure in their probe function.
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For example, the QLogic qla2xxx driver sets the needs_freset bit for certain
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PCI card types:
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PCI card types::
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+ /* Set EEH reset type to fundamental if required by hba */
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+ if (IS_QLA24XX(ha) || IS_QLA25XX(ha) || IS_QLA81XX(ha))
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+ pdev->needs_freset = 1;
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+
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+ /* Set EEH reset type to fundamental if required by hba */
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+ if (IS_QLA24XX(ha) || IS_QLA25XX(ha) || IS_QLA81XX(ha))
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+ pdev->needs_freset = 1;
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+
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Platform proceeds either to STEP 5 (Resume Operations) or STEP 6 (Permanent
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Failure).
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>>> The current powerpc implementation does not try a power-cycle
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>>> reset if the driver returned PCI_ERS_RESULT_DISCONNECT.
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>>> However, it probably should.
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.. note::
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The current powerpc implementation does not try a power-cycle
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reset if the driver returned PCI_ERS_RESULT_DISCONNECT.
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However, it probably should.
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STEP 5: Resume Operations
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@ -370,44 +382,43 @@ The current policy is to turn this into a platform policy.
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That is, the recovery API only requires that:
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- There is no guarantee that interrupt delivery can proceed from any
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device on the segment starting from the error detection and until the
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slot_reset callback is called, at which point interrupts are expected
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to be fully operational.
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device on the segment starting from the error detection and until the
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slot_reset callback is called, at which point interrupts are expected
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to be fully operational.
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- There is no guarantee that interrupt delivery is stopped, that is,
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a driver that gets an interrupt after detecting an error, or that detects
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an error within the interrupt handler such that it prevents proper
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ack'ing of the interrupt (and thus removal of the source) should just
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return IRQ_NOTHANDLED. It's up to the platform to deal with that
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condition, typically by masking the IRQ source during the duration of
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the error handling. It is expected that the platform "knows" which
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interrupts are routed to error-management capable slots and can deal
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with temporarily disabling that IRQ number during error processing (this
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isn't terribly complex). That means some IRQ latency for other devices
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sharing the interrupt, but there is simply no other way. High end
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platforms aren't supposed to share interrupts between many devices
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anyway :)
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a driver that gets an interrupt after detecting an error, or that detects
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an error within the interrupt handler such that it prevents proper
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ack'ing of the interrupt (and thus removal of the source) should just
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return IRQ_NOTHANDLED. It's up to the platform to deal with that
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condition, typically by masking the IRQ source during the duration of
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the error handling. It is expected that the platform "knows" which
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interrupts are routed to error-management capable slots and can deal
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with temporarily disabling that IRQ number during error processing (this
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isn't terribly complex). That means some IRQ latency for other devices
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sharing the interrupt, but there is simply no other way. High end
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platforms aren't supposed to share interrupts between many devices
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anyway :)
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>>> Implementation details for the powerpc platform are discussed in
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>>> the file Documentation/powerpc/eeh-pci-error-recovery.txt
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.. note::
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>>> As of this writing, there is a growing list of device drivers with
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>>> patches implementing error recovery. Not all of these patches are in
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>>> mainline yet. These may be used as "examples":
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>>>
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>>> drivers/scsi/ipr
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>>> drivers/scsi/sym53c8xx_2
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>>> drivers/scsi/qla2xxx
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>>> drivers/scsi/lpfc
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>>> drivers/next/bnx2.c
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>>> drivers/next/e100.c
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>>> drivers/net/e1000
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>>> drivers/net/e1000e
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>>> drivers/net/ixgb
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>>> drivers/net/ixgbe
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>>> drivers/net/cxgb3
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>>> drivers/net/s2io.c
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>>> drivers/net/qlge
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Implementation details for the powerpc platform are discussed in
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the file Documentation/powerpc/eeh-pci-error-recovery.txt
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The End
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-------
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As of this writing, there is a growing list of device drivers with
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patches implementing error recovery. Not all of these patches are in
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mainline yet. These may be used as "examples":
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- drivers/scsi/ipr
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- drivers/scsi/sym53c8xx_2
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- drivers/scsi/qla2xxx
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- drivers/scsi/lpfc
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- drivers/next/bnx2.c
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- drivers/next/e100.c
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- drivers/net/e1000
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- drivers/net/e1000e
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- drivers/net/ixgb
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- drivers/net/ixgbe
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- drivers/net/cxgb3
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- drivers/net/s2io.c
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- drivers/net/qlge
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@ -12143,7 +12143,7 @@ M: Sam Bobroff <sbobroff@linux.ibm.com>
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M: Oliver O'Halloran <oohall@gmail.com>
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L: linuxppc-dev@lists.ozlabs.org
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S: Supported
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F: Documentation/PCI/pci-error-recovery.txt
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F: Documentation/PCI/pci-error-recovery.rst
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F: drivers/pci/pcie/aer.c
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F: drivers/pci/pcie/dpc.c
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F: drivers/pci/pcie/err.c
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@ -12156,7 +12156,7 @@ PCI ERROR RECOVERY
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M: Linas Vepstas <linasvepstas@gmail.com>
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L: linux-pci@vger.kernel.org
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S: Supported
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F: Documentation/PCI/pci-error-recovery.txt
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F: Documentation/PCI/pci-error-recovery.rst
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PCI MSI DRIVER FOR ALTERA MSI IP
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M: Ley Foon Tan <lftan@altera.com>
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