PCI: doc/pci: create Documentation/PCI/ and move files into it

Create Documentation/PCI/ and move PCI-related files to it.
Fix a few instances of trailing whitespace.
Update references to the new file locations.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 0 insertions, 396 deletions

diff --git a/Documentation/pci-error-recovery.txt b/Documentation/pci-error-recovery.txt
deleted file mode 100644
index 6650af43252..00000000000
--- a/Documentation/pci-error-recovery.txt
+++ /dev/null
@@ -1,396 +0,0 @@
-
-                       PCI Error Recovery
-                       ------------------
-                        February 2, 2006
-
-                 Current document maintainer:
-             Linas Vepstas <linas@austin.ibm.com>
-
-
-Many PCI bus controllers are able to detect a variety of hardware
-PCI errors on the bus, such as parity errors on the data and address
-busses, as well as SERR and PERR errors.  Some of the more advanced
-chipsets are able to deal with these errors; these include PCI-E chipsets,
-and the PCI-host bridges found on IBM Power4 and Power5-based pSeries
-boxes. A typical action taken is to disconnect the affected device,
-halting all I/O to it.  The goal of a disconnection is to avoid system
-corruption; for example, to halt system memory corruption due to DMA's
-to "wild" addresses. Typically, a reconnection mechanism is also
-offered, so that the affected PCI device(s) are reset and put back
-into working condition. The reset phase requires coordination
-between the affected device drivers and the PCI controller chip.
-This document describes a generic API for notifying device drivers
-of a bus disconnection, and then performing error recovery.
-This API is currently implemented in the 2.6.16 and later kernels.
-
-Reporting and recovery is performed in several steps. First, when
-a PCI hardware error has resulted in a bus disconnect, that event
-is reported as soon as possible to all affected device drivers,
-including multiple instances of a device driver on multi-function
-cards. This allows device drivers to avoid deadlocking in spinloops,
-waiting for some i/o-space register to change, when it never will.
-It also gives the drivers a chance to defer incoming I/O as
-needed.
-
-Next, recovery is performed in several stages. Most of the complexity
-is forced by the need to handle multi-function devices, that is,
-devices that have multiple device drivers associated with them.
-In the first stage, each driver is allowed to indicate what type
-of reset it desires, the choices being a simple re-enabling of I/O
-or requesting a hard reset (a full electrical #RST of the PCI card).
-If any driver requests a full reset, that is what will be done.
-
-After a full reset and/or a re-enabling of I/O, all drivers are
-again notified, so that they may then perform any device setup/config
-that may be required.  After these have all completed, a final
-"resume normal operations" event is sent out.
-
-The biggest reason for choosing a kernel-based implementation rather
-than a user-space implementation was the need to deal with bus
-disconnects of PCI devices attached to storage media, and, in particular,
-disconnects from devices holding the root file system.  If the root
-file system is disconnected, a user-space mechanism would have to go
-through a large number of contortions to complete recovery. Almost all
-of the current Linux file systems are not tolerant of disconnection
-from/reconnection to their underlying block device. By contrast,
-bus errors are easy to manage in the device driver. Indeed, most
-device drivers already handle very similar recovery procedures;
-for example, the SCSI-generic layer already provides significant
-mechanisms for dealing with SCSI bus errors and SCSI bus resets.
-
-
-Detailed Design
----------------
-Design and implementation details below, based on a chain of
-public email discussions with Ben Herrenschmidt, circa 5 April 2005.
-
-The error recovery API support is exposed to the driver in the form of
-a structure of function pointers pointed to by a new field in struct
-pci_driver. A driver that fails to provide the structure is "non-aware",
-and the actual recovery steps taken are platform dependent.  The
-arch/powerpc implementation will simulate a PCI hotplug remove/add.
-
-This structure has the form:
-struct pci_error_handlers
-{
-	int (*error_detected)(struct pci_dev *dev, enum pci_channel_state);
-	int (*mmio_enabled)(struct pci_dev *dev);
-	int (*link_reset)(struct pci_dev *dev);
-	int (*slot_reset)(struct pci_dev *dev);
-	void (*resume)(struct pci_dev *dev);
-};
-
-The possible channel states are:
-enum pci_channel_state {
-	pci_channel_io_normal,  /* I/O channel is in normal state */
-	pci_channel_io_frozen,  /* I/O to channel is blocked */
-	pci_channel_io_perm_failure, /* PCI card is dead */
-};
-
-Possible return values are:
-enum pci_ers_result {
-	PCI_ERS_RESULT_NONE,        /* no result/none/not supported in device driver */
-	PCI_ERS_RESULT_CAN_RECOVER, /* Device driver can recover without slot reset */
-	PCI_ERS_RESULT_NEED_RESET,  /* Device driver wants slot to be reset. */
-	PCI_ERS_RESULT_DISCONNECT,  /* Device has completely failed, is unrecoverable */
-	PCI_ERS_RESULT_RECOVERED,   /* Device driver is fully recovered and operational */
-};
-
-A driver does not have to implement all of these callbacks; however,
-if it implements any, it must implement error_detected(). If a callback
-is not implemented, the corresponding feature is considered unsupported.
-For example, if mmio_enabled() and resume() aren't there, then it
-is assumed that the driver is not doing any direct recovery and requires
-a reset. If link_reset() is not implemented, the card is assumed as
-not care about link resets. Typically a driver will want to know about
-a slot_reset().
-
-The actual steps taken by a platform to recover from a PCI error
-event will be platform-dependent, but will follow the general
-sequence described below.
-
-STEP 0: Error Event
--------------------
-PCI bus error is detect by the PCI hardware.  On powerpc, the slot
-is isolated, in that all I/O is blocked: all reads return 0xffffffff,
-all writes are ignored.
-
-
-STEP 1: Notification
---------------------
-Platform calls the error_detected() callback on every instance of
-every driver affected by the error.
-
-At this point, the device might not be accessible anymore, depending on
-the platform (the slot will be isolated on powerpc). The driver may
-already have "noticed" the error because of a failing I/O, but this
-is the proper "synchronization point", that is, it gives the driver
-a chance to cleanup, waiting for pending stuff (timers, whatever, etc...)
-to complete; it can take semaphores, schedule, etc... everything but
-touch the device. Within this function and after it returns, the driver
-shouldn't do any new IOs. Called in task context. This is sort of a
-"quiesce" point. See note about interrupts at the end of this doc.
-
-All drivers participating in this system must implement this call.
-The driver must return one of the following result codes:
-		- PCI_ERS_RESULT_CAN_RECOVER:
-		  Driver returns this if it thinks it might be able to recover
-		  the HW by just banging IOs or if it wants to be given
-		  a chance to extract some diagnostic information (see
-		  mmio_enable, below).
-		- PCI_ERS_RESULT_NEED_RESET:
-		  Driver returns this if it can't recover without a hard
-		  slot reset.
-		- PCI_ERS_RESULT_DISCONNECT:
-		  Driver returns this if it doesn't want to recover at all.
-
-The next step taken will depend on the result codes returned by the
-drivers.
-
-If all drivers on the segment/slot return PCI_ERS_RESULT_CAN_RECOVER,
-then the platform should re-enable IOs on the slot (or do nothing in
-particular, if the platform doesn't isolate slots), and recovery
-proceeds to STEP 2 (MMIO Enable).
-
-If any driver requested a slot reset (by returning PCI_ERS_RESULT_NEED_RESET),
-then recovery proceeds to STEP 4 (Slot Reset).
-
-If the platform is unable to recover the slot, the next step
-is STEP 6 (Permanent Failure).
-
->>> The current powerpc implementation assumes that a device driver will
->>> *not* schedule or semaphore in this routine; the current powerpc
->>> implementation uses one kernel thread to notify all devices;
->>> thus, if one device sleeps/schedules, all devices are affected.
->>> Doing better requires complex multi-threaded logic in the error
->>> recovery implementation (e.g. waiting for all notification threads
->>> to "join" before proceeding with recovery.)  This seems excessively
->>> complex and not worth implementing.
-
->>> The current powerpc implementation doesn't much care if the device
->>> attempts I/O at this point, or not.  I/O's will fail, returning
->>> a value of 0xff on read, and writes will be dropped. If the device
->>> driver attempts more than 10K I/O's to a frozen adapter, it will
->>> assume that the device driver has gone into an infinite loop, and
->>> it will panic the kernel. There doesn't seem to be any other
->>> way of stopping a device driver that insists on spinning on I/O.
-
-STEP 2: MMIO Enabled
--------------------
-The platform re-enables MMIO to the device (but typically not the
-DMA), and then calls the mmio_enabled() callback on all affected
-device drivers.
-
-This is the "early recovery" call. IOs are allowed again, but DMA is
-not (hrm... to be discussed, I prefer not), with some restrictions. This
-is NOT a callback for the driver to start operations again, only to
-peek/poke at the device, extract diagnostic information, if any, and
-eventually do things like trigger a device local reset or some such,
-but not restart operations. This is callback is made if all drivers on
-a segment agree that they can try to recover and if no automatic link reset
-was performed by the HW. If the platform can't just re-enable IOs without
-a slot reset or a link reset, it wont call this callback, and instead
-will have gone directly to STEP 3 (Link Reset) or STEP 4 (Slot Reset)
-
->>> The following is proposed; no platform implements this yet:
->>> Proposal: All I/O's should be done _synchronously_ from within
->>> this callback, errors triggered by them will be returned via
->>> the normal pci_check_whatever() API, no new error_detected()
->>> callback will be issued due to an error happening here. However,
->>> such an error might cause IOs to be re-blocked for the whole
->>> segment, and thus invalidate the recovery that other devices
->>> on the same segment might have done, forcing the whole segment
->>> into one of the next states, that is, link reset or slot reset.
-
-The driver should return one of the following result codes:
-		- PCI_ERS_RESULT_RECOVERED
-		  Driver returns this if it thinks the device is fully
-		  functional and thinks it is ready to start
-		  normal driver operations again. There is no
-		  guarantee that the driver will actually be
-		  allowed to proceed, as another driver on the
-		  same segment might have failed and thus triggered a
-		  slot reset on platforms that support it.
-
-		- PCI_ERS_RESULT_NEED_RESET
-		  Driver returns this if it thinks the device is not
-		  recoverable in it's current state and it needs a slot
-		  reset to proceed.
-
-		- PCI_ERS_RESULT_DISCONNECT
-		  Same as above. Total failure, no recovery even after
-		  reset driver dead. (To be defined more precisely)
-
-The next step taken depends on the results returned by the drivers.
-If all drivers returned PCI_ERS_RESULT_RECOVERED, then the platform
-proceeds to either STEP3 (Link Reset) or to STEP 5 (Resume Operations).
-
-If any driver returned PCI_ERS_RESULT_NEED_RESET, then the platform
-proceeds to STEP 4 (Slot Reset)
-
->>> The current powerpc implementation does not implement this callback.
-
-
-STEP 3: Link Reset
-------------------
-The platform resets the link, and then calls the link_reset() callback
-on all affected device drivers.  This is a PCI-Express specific state
-and is done whenever a non-fatal error has been detected that can be
-"solved" by resetting the link. This call informs the driver of the
-reset and the driver should check to see if the device appears to be
-in working condition.
-
-The driver is not supposed to restart normal driver I/O operations
-at this point.  It should limit itself to "probing" the device to
-check it's recoverability status. If all is right, then the platform
-will call resume() once all drivers have ack'd link_reset().
-
-	Result codes:
-		(identical to STEP 3 (MMIO Enabled)
-
-The platform then proceeds to either STEP 4 (Slot Reset) or STEP 5
-(Resume Operations).
-
->>> The current powerpc implementation does not implement this callback.
-
-
-STEP 4: Slot Reset
-------------------
-The platform performs a soft or hard reset of the device, and then
-calls the slot_reset() callback.
-
-A soft reset consists of asserting the adapter #RST line and then
-restoring the PCI BAR's and PCI configuration header to a state
-that is equivalent to what it would be after a fresh system
-power-on followed by power-on BIOS/system firmware initialization.
-If the platform supports PCI hotplug, then the reset might be
-performed by toggling the slot electrical power off/on.
-
-It is important for the platform to restore the PCI config space
-to the "fresh poweron" state, rather than the "last state". After
-a slot reset, the device driver will almost always use its standard
-device initialization routines, and an unusual config space setup
-may result in hung devices, kernel panics, or silent data corruption.
-
-This call gives drivers the chance to re-initialize the hardware
-(re-download firmware, etc.).  At this point, the driver may assume
-that he card is in a fresh state and is fully functional. In
-particular, interrupt generation should work normally.
-
-Drivers should not yet restart normal I/O processing operations
-at this point.  If all device drivers report success on this
-callback, the platform will call resume() to complete the sequence,
-and let the driver restart normal I/O processing.
-
-A driver can still return a critical failure for this function if
-it can't get the device operational after reset.  If the platform
-previously tried a soft reset, it might now try a hard reset (power
-cycle) and then call slot_reset() again.  It the device still can't
-be recovered, there is nothing more that can be done;  the platform
-will typically report a "permanent failure" in such a case.  The
-device will be considered "dead" in this case.
-
-Drivers for multi-function cards will need to coordinate among
-themselves as to which driver instance will perform any "one-shot"
-or global device initialization. For example, the Symbios sym53cxx2
-driver performs device init only from PCI function 0:
-
-+       if (PCI_FUNC(pdev->devfn) == 0)
-+               sym_reset_scsi_bus(np, 0);
-
-	Result codes:
-		- PCI_ERS_RESULT_DISCONNECT
-		Same as above.
-
-Platform proceeds either to STEP 5 (Resume Operations) or STEP 6 (Permanent
-Failure).
-
->>> The current powerpc implementation does not currently try a
->>> power-cycle reset if the driver returned PCI_ERS_RESULT_DISCONNECT.
->>> However, it probably should.
-
-
-STEP 5: Resume Operations
--------------------------
-The platform will call the resume() callback on all affected device
-drivers if all drivers on the segment have returned
-PCI_ERS_RESULT_RECOVERED from one of the 3 previous callbacks.
-The goal of this callback is to tell the driver to restart activity,
-that everything is back and running. This callback does not return
-a result code.
-
-At this point, if a new error happens, the platform will restart
-a new error recovery sequence.
-
-STEP 6: Permanent Failure
--------------------------
-A "permanent failure" has occurred, and the platform cannot recover
-the device.  The platform will call error_detected() with a
-pci_channel_state value of pci_channel_io_perm_failure.
-
-The device driver should, at this point, assume the worst. It should
-cancel all pending I/O, refuse all new I/O, returning -EIO to
-higher layers. The device driver should then clean up all of its
-memory and remove itself from kernel operations, much as it would
-during system shutdown.
-
-The platform will typically notify the system operator of the
-permanent failure in some way.  If the device is hotplug-capable,
-the operator will probably want to remove and replace the device.
-Note, however, not all failures are truly "permanent". Some are
-caused by over-heating, some by a poorly seated card. Many
-PCI error events are caused by software bugs, e.g. DMA's to
-wild addresses or bogus split transactions due to programming
-errors. See the discussion in powerpc/eeh-pci-error-recovery.txt
-for additional detail on real-life experience of the causes of
-software errors.
-
-
-Conclusion; General Remarks
----------------------------
-The way those callbacks are called is platform policy. A platform with
-no slot reset capability may want to just "ignore" drivers that can't
-recover (disconnect them) and try to let other cards on the same segment
-recover. Keep in mind that in most real life cases, though, there will
-be only one driver per segment.
-
-Now, a note about interrupts. If you get an interrupt and your
-device is dead or has been isolated, there is a problem :)
-The current policy is to turn this into a platform policy.
-That is, the recovery API only requires that:
-
- - There is no guarantee that interrupt delivery can proceed from any
-device on the segment starting from the error detection and until the
-resume callback is sent, at which point interrupts are expected to be
-fully operational.
-
- - There is no guarantee that interrupt delivery is stopped, that is,
-a driver that gets an interrupt after detecting an error, or that detects
-an error within the interrupt handler such that it prevents proper
-ack'ing of the interrupt (and thus removal of the source) should just
-return IRQ_NOTHANDLED. It's up to the platform to deal with that
-condition, typically by masking the IRQ source during the duration of
-the error handling. It is expected that the platform "knows" which
-interrupts are routed to error-management capable slots and can deal
-with temporarily disabling that IRQ number during error processing (this
-isn't terribly complex). That means some IRQ latency for other devices
-sharing the interrupt, but there is simply no other way. High end
-platforms aren't supposed to share interrupts between many devices
-anyway :)
-
->>> Implementation details for the powerpc platform are discussed in
->>> the file Documentation/powerpc/eeh-pci-error-recovery.txt
-
->>> As of this writing, there are six device drivers with patches
->>> implementing error recovery. Not all of these patches are in
->>> mainline yet. These may be used as "examples":
->>>
->>> drivers/scsi/ipr.c
->>> drivers/scsi/sym53cxx_2
->>> drivers/next/e100.c
->>> drivers/net/e1000
->>> drivers/net/ixgb
->>> drivers/net/s2io.c
-
-The End
--------