Message-ID: <20190513115600.60e59e5e@coco.lan>
Date:   Mon, 13 May 2019 11:56:00 -0300
From:   Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
To:     Changbin Du <changbin.du@...il.com>
Cc:     bhelgaas@...gle.com, corbet@....net, linux-pci@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 07/12] Documentation: PCI: convert
 pci-error-recovery.txt to reST

Em Mon, 13 May 2019 22:19:55 +0800
Changbin Du <changbin.du@...il.com> escreveu:

> This converts the plain text documentation to reStructuredText format and
> add it to Sphinx TOC tree. No essential content change.
> 
> Signed-off-by: Changbin Du <changbin.du@...il.com>
> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>

Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>

> ---
>  Documentation/PCI/index.rst                   |   1 +
>  ...or-recovery.txt => pci-error-recovery.rst} | 287 +++++++++---------
>  MAINTAINERS                                   |   4 +-
>  3 files changed, 152 insertions(+), 140 deletions(-)
>  rename Documentation/PCI/{pci-error-recovery.txt => pci-error-recovery.rst} (67%)
> 
> diff --git a/Documentation/PCI/index.rst b/Documentation/PCI/index.rst
> index 6f573f3df993..92e62d0fc9e6 100644
> --- a/Documentation/PCI/index.rst
> +++ b/Documentation/PCI/index.rst
> @@ -13,3 +13,4 @@ Linux PCI Bus Subsystem
>     pci-iov-howto
>     msi-howto
>     acpi-info
> +   pci-error-recovery
> diff --git a/Documentation/PCI/pci-error-recovery.txt b/Documentation/PCI/pci-error-recovery.rst
> similarity index 67%
> rename from Documentation/PCI/pci-error-recovery.txt
> rename to Documentation/PCI/pci-error-recovery.rst
> index 0b6bb3ef449e..83db42092935 100644
> --- a/Documentation/PCI/pci-error-recovery.txt
> +++ b/Documentation/PCI/pci-error-recovery.rst
> @@ -1,12 +1,13 @@
> +.. SPDX-License-Identifier: GPL-2.0
>  
> -                       PCI Error Recovery
> -                       ------------------
> -                        February 2, 2006
> +==================
> +PCI Error Recovery
> +==================
>  
> -                 Current document maintainer:
> -             Linas Vepstas <linasvepstas@...il.com>
> -          updated by Richard Lary <rlary@...ibm.com>
> -       and Mike Mason <mmlnx@...ibm.com> on 27-Jul-2009
> +
> +:Authors: - Linas Vepstas <linasvepstas@...il.com>
> +          - Richard Lary <rlary@...ibm.com>
> +          - Mike Mason <mmlnx@...ibm.com>
>  
>  
>  Many PCI bus controllers are able to detect a variety of hardware
> @@ -63,7 +64,8 @@ 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.
>  
> @@ -73,30 +75,33 @@ 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 (*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 */
> -};
> +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 (*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
> @@ -134,16 +139,17 @@ shouldn't do any new IOs. Called in task context. This is sort of a
>  
>  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
> -		  slot reset.
> -		- PCI_ERS_RESULT_DISCONNECT:
> -		  Driver returns this if it doesn't want to recover at all.
> +
> +  - 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
> +      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.
> @@ -159,25 +165,27 @@ 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 more than
> ->>> EEH_MAX_FAILS I/O's are attempted to a frozen adapter, EEH
> ->>> assumes that the device driver has gone into an infinite loop
> ->>> and prints an error to syslog.  A reboot is then required to
> ->>> get the device working again.
> +.. note::
> +
> +   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 more than
> +   EEH_MAX_FAILS I/O's are attempted to a frozen adapter, EEH
> +   assumes that the device driver has gone into an infinite loop
> +   and prints an error to syslog.  A reboot is then required to
> +   get the device working again.
>  
>  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.
> @@ -192,34 +200,36 @@ 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 will not 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.
> +.. note::
> +
> +   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 its 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)
> +  - 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 its 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
> @@ -293,31 +303,33 @@ 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:
> +driver performs device init only from PCI function 0::
>  
> -+       if (PCI_FUNC(pdev->devfn) == 0)
> -+               sym_reset_scsi_bus(np, 0);
> +	+       if (PCI_FUNC(pdev->devfn) == 0)
> +	+               sym_reset_scsi_bus(np, 0);
>  
> -	Result codes:
> -		- PCI_ERS_RESULT_DISCONNECT
> -		Same as above.
> +Result codes:
> +	- PCI_ERS_RESULT_DISCONNECT
> +	  Same as above.
>  
>  Drivers for PCI Express cards that require a fundamental reset must
>  set the needs_freset bit in the pci_dev structure in their probe function.
>  For example, the QLogic qla2xxx driver sets the needs_freset bit for certain
> -PCI card types:
> +PCI card types::
>  
> -+	/* Set EEH reset type to fundamental if required by hba  */
> -+	if (IS_QLA24XX(ha) || IS_QLA25XX(ha) || IS_QLA81XX(ha))
> -+		pdev->needs_freset = 1;
> -+
> +	+	/* Set EEH reset type to fundamental if required by hba  */
> +	+	if (IS_QLA24XX(ha) || IS_QLA25XX(ha) || IS_QLA81XX(ha))
> +	+		pdev->needs_freset = 1;
> +	+
>  
>  Platform proceeds either to STEP 5 (Resume Operations) or STEP 6 (Permanent
>  Failure).
>  
> ->>> The current powerpc implementation does not try a power-cycle
> ->>> reset if the driver returned PCI_ERS_RESULT_DISCONNECT.
> ->>> However, it probably should.
> +.. note::
> +
> +   The current powerpc implementation does not try a power-cycle
> +   reset if the driver returned PCI_ERS_RESULT_DISCONNECT.
> +   However, it probably should.
>  
>  
>  STEP 5: Resume Operations
> @@ -370,44 +382,43 @@ 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
> -slot_reset callback is called, at which point interrupts are expected
> -to be fully operational.
> +   device on the segment starting from the error detection and until the
> +   slot_reset callback is called, 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 is a growing list of 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
> ->>> drivers/scsi/sym53c8xx_2
> ->>> drivers/scsi/qla2xxx
> ->>> drivers/scsi/lpfc
> ->>> drivers/next/bnx2.c
> ->>> drivers/next/e100.c
> ->>> drivers/net/e1000
> ->>> drivers/net/e1000e
> ->>> drivers/net/ixgb
> ->>> drivers/net/ixgbe
> ->>> drivers/net/cxgb3
> ->>> drivers/net/s2io.c
> ->>> drivers/net/qlge
> -
> -The End
> --------
> +   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 :)
> +
> +.. note::
> +
> +   Implementation details for the powerpc platform are discussed in
> +   the file Documentation/powerpc/eeh-pci-error-recovery.txt
> +
> +   As of this writing, there is a growing list of 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
> +   - drivers/scsi/sym53c8xx_2
> +   - drivers/scsi/qla2xxx
> +   - drivers/scsi/lpfc
> +   - drivers/next/bnx2.c
> +   - drivers/next/e100.c
> +   - drivers/net/e1000
> +   - drivers/net/e1000e
> +   - drivers/net/ixgb
> +   - drivers/net/ixgbe
> +   - drivers/net/cxgb3
> +   - drivers/net/s2io.c
> +   - drivers/net/qlge
> diff --git a/MAINTAINERS b/MAINTAINERS
> index fb9f9d71f7a2..6e5ec5d3987e 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12101,7 +12101,7 @@ M:	Sam Bobroff <sbobroff@...ux.ibm.com>
>  M:	Oliver O'Halloran <oohall@...il.com>
>  L:	linuxppc-dev@...ts.ozlabs.org
>  S:	Supported
> -F:	Documentation/PCI/pci-error-recovery.txt
> +F:	Documentation/PCI/pci-error-recovery.rst
>  F:	drivers/pci/pcie/aer.c
>  F:	drivers/pci/pcie/dpc.c
>  F:	drivers/pci/pcie/err.c
> @@ -12114,7 +12114,7 @@ PCI ERROR RECOVERY
>  M:	Linas Vepstas <linasvepstas@...il.com>
>  L:	linux-pci@...r.kernel.org
>  S:	Supported
> -F:	Documentation/PCI/pci-error-recovery.txt
> +F:	Documentation/PCI/pci-error-recovery.rst
>  
>  PCI MSI DRIVER FOR ALTERA MSI IP
>  M:	Ley Foon Tan <lftan@...era.com>



Thanks,
Mauro

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