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From: <Austin.Bolen@dell.com>
To: <helgaas@kernel.org>, <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: <Austin.Bolen@dell.com>, <linux-pci@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <ashok.raj@intel.com>
Subject: Re: [PATCH v17 09/12] PCI/AER: Allow clearing Error Status Register in FF mode
Date: Thu, 12 Mar 2020 21:02:28 +0000	[thread overview]
Message-ID: <161a5d15809b47b09200f1806484b907@AUSX13MPC107.AMER.DELL.COM> (raw)
In-Reply-To: 20200312195319.GA162308@google.com

On 3/12/2020 2:53 PM, Bjorn Helgaas wrote:
> 
> [EXTERNAL EMAIL]
> 
> On Wed, Mar 11, 2020 at 04:07:59PM -0700, Kuppuswamy Sathyanarayanan wrote:
>> On 3/11/20 3:23 PM, Bjorn Helgaas wrote:
>>> Is any synchronization needed here between the EDR path and the
>>> hotplug/enumeration path?
>>
>> If we want to follow the implementation note step by step (in
>> sequence) then we need some synchronization between EDR path and
>> enumeration path. But if it's OK to achieve the same end result by
>> following steps out of sequence then we don't need to create any
>> dependency between EDR and enumeration paths. Currently we follow
>> the latter approach.
> 
> What would the synchronization look like?
> 
> Ideally I think it would be better to follow the order in the
> flowchart if it's not too onerous.  That will make the code easier to
> understand.  The current situation with this dependency on pciehp and
> what it will do leaves a lot of things implicit.
> 
> What happens if CONFIG_PCIE_EDR=y but CONFIG_HOTPLUG_PCI_PCIE=n?
> 
> IIUC, when DPC triggers, pciehp is what fields the DLLSC interrupt and
> unbinds the drivers and removes the devices.  If that doesn't happen,
> and Linux clears the DPC trigger to bring the link back up, will those
> drivers try to operate uninitialized devices?
> 
> Does EDR need a dependency on CONFIG_HOTPLUG_PCI_PCIE?

 From one of Sathya's other responses:

"If hotplug is not supported then there is support to enumerate
devices via polling  or ACPI events. But a point to note
here is, enumeration path is independent of error handler path, and
hence there is no explicit trigger or event from error handler path
to enumeration path to kick start the enumeration."

The EDR standard doesn't have any dependency on hot-plug. It sounds like 
in the current implementation there's some manual intervention needed if 
hot-plug is not supported? Ideally recovery would kick in automatically 
but requiring manual intervention is a good first step.

> 
>> For example, consider the case in flow chart where after sending
>> success _OST, firmware decides to stop the recovery of the device.
>>
>> if we follow the flow chart as is then the steps should be,
>>
>> 1. clear the DPC status trigger
>> 2. Send success code via _OST, and wait for return from _OST
>> 3. if successful return then enumerate the child devices and
>> reassign bus numbers.
>>
>> In current approach the steps followed are,
>>
>> 1. Clear the DPC status trigger.
>> 2. Send success code via _OST

Success in step 2 is assuming device trained and config space is 
accessible correct?  If device was removed or device config space is not 
accessible then failure status should be sent via _OST.

>> 2. In parallel, LINK UP event path will enumerate the child devices.
>> 3. if firmware decides not to recover the device, then LINK DOWN
>> event will eventually remove them again.
> 



  reply	other threads:[~2020-03-12 21:02 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-04  2:36 [PATCH v17 00/12] Add Error Disconnect Recover (EDR) support sathyanarayanan.kuppuswamy
2020-03-04  2:36 ` [PATCH v17 01/12] PCI/ERR: Update error status after reset_link() sathyanarayanan.kuppuswamy
2020-03-04  2:36 ` [PATCH v17 02/12] PCI/AER: Move pci_cleanup_aer_error_status_regs() declaration to pci.h sathyanarayanan.kuppuswamy
2020-03-04  2:36 ` [PATCH v17 03/12] PCI/ERR: Remove service dependency in pcie_do_recovery() sathyanarayanan.kuppuswamy
2020-03-17 14:40   ` Christoph Hellwig
2020-03-04  2:36 ` [PATCH v17 04/12] PCI: portdrv: remove unnecessary pcie_port_find_service() sathyanarayanan.kuppuswamy
2020-03-04  2:36 ` [PATCH v17 05/12] PCI: portdrv: remove reset_link member from pcie_port_service_driver sathyanarayanan.kuppuswamy
2020-03-17 14:41   ` Christoph Hellwig
2020-03-17 14:55     ` Kuppuswamy, Sathyanarayanan
2020-03-04  2:36 ` [PATCH v17 06/12] Documentation: PCI: Remove reset_link references sathyanarayanan.kuppuswamy
2020-03-17 14:42   ` Christoph Hellwig
2020-03-17 15:05     ` Kuppuswamy, Sathyanarayanan
2020-03-17 15:07       ` Christoph Hellwig
2020-03-17 16:03         ` Bjorn Helgaas
2020-03-17 17:06           ` Christoph Hellwig
2020-03-19 22:52             ` Bjorn Helgaas
2020-03-04  2:36 ` [PATCH v17 07/12] PCI/ERR: Return status of pcie_do_recovery() sathyanarayanan.kuppuswamy
2020-03-04  2:36 ` [PATCH v17 08/12] PCI/DPC: Cache DPC capabilities in pci_init_capabilities() sathyanarayanan.kuppuswamy
2020-03-04  2:36 ` [PATCH v17 09/12] PCI/AER: Allow clearing Error Status Register in FF mode sathyanarayanan.kuppuswamy
2020-03-06  5:45   ` Kuppuswamy, Sathyanarayanan
2020-03-06 16:04     ` Bjorn Helgaas
2020-03-06 16:11       ` Kuppuswamy, Sathyanarayanan
2020-03-06 16:41         ` Bjorn Helgaas
2020-03-10  2:40   ` Bjorn Helgaas
2020-03-10  4:28     ` Kuppuswamy, Sathyanarayanan
2020-03-10 18:14       ` Austin.Bolen
2020-03-10 19:32         ` Bjorn Helgaas
2020-03-10 20:06           ` Austin.Bolen
2020-03-10 20:41             ` Kuppuswamy Sathyanarayanan
2020-03-10 20:41               ` Kuppuswamy Sathyanarayanan
2020-03-10 20:49               ` Austin.Bolen
2020-03-11 14:45             ` Bjorn Helgaas
2020-03-11 15:19               ` Austin.Bolen
2020-03-11 17:12                 ` Bjorn Helgaas
2020-03-11 17:27                   ` Austin.Bolen
2020-03-11 20:33                     ` Bjorn Helgaas
2020-03-11 21:25                       ` Kuppuswamy Sathyanarayanan
2020-03-11 21:53                         ` Austin.Bolen
2020-03-11 22:11                           ` Kuppuswamy Sathyanarayanan
2020-03-11 22:23                             ` Bjorn Helgaas
2020-03-11 23:07                               ` Kuppuswamy Sathyanarayanan
2020-03-12 19:53                                 ` Bjorn Helgaas
2020-03-12 21:02                                   ` Austin.Bolen [this message]
2020-03-12 21:29                                     ` Kuppuswamy Sathyanarayanan
2020-03-12 21:52                                       ` Bjorn Helgaas
2020-03-12 22:02                                         ` Kuppuswamy Sathyanarayanan
2020-03-12 22:36                                           ` Bjorn Helgaas
2020-03-12 21:59                                   ` Kuppuswamy Sathyanarayanan
2020-03-12 22:32                                     ` Bjorn Helgaas
2020-03-13  6:22                                       ` Kuppuswamy, Sathyanarayanan
2020-03-13 19:28                                         ` Bjorn Helgaas
2020-03-13 20:26                                           ` Kuppuswamy Sathyanarayanan
2020-03-19 23:03                                             ` Bjorn Helgaas
2020-03-19 23:20                                               ` Kuppuswamy, Sathyanarayanan
2020-03-11 22:13                         ` Bjorn Helgaas
2020-03-11 22:41                           ` Kuppuswamy Sathyanarayanan
2020-03-11 18:12                   ` Kuppuswamy Sathyanarayanan
2020-03-11 22:05             ` Bjorn Helgaas
2020-03-04  2:36 ` [PATCH v17 10/12] PCI/DPC: Export DPC error recovery functions sathyanarayanan.kuppuswamy
2020-03-17 14:43   ` Christoph Hellwig
2020-03-04  2:36 ` [PATCH v17 11/12] PCI/DPC: Add Error Disconnect Recover (EDR) support sathyanarayanan.kuppuswamy
2020-03-06  3:47   ` Bjorn Helgaas
2020-03-06  6:32     ` Kuppuswamy, Sathyanarayanan
2020-03-06 21:00       ` Bjorn Helgaas
2020-03-06 22:42         ` Kuppuswamy Sathyanarayanan
2020-03-06 23:23           ` Bjorn Helgaas
2020-03-07  0:19             ` Kuppuswamy Sathyanarayanan
2020-03-04  2:36 ` [PATCH v17 12/12] PCI/ACPI: Enable EDR support sathyanarayanan.kuppuswamy

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