Re: [PATCH v3 1/1] PCI/ERR: Fix reset logic in pcie_do_recovery() call

["Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@linux.intel.com>]

On 9/22/20 4:33 PM, Bjorn Helgaas wrote:
> On Tue, Sep 22, 2020 at 02:44:51PM -0700, Kuppuswamy, Sathyanarayanan wrote:
>>
>>
>> On 9/22/20 11:52 AM, Bjorn Helgaas wrote:
>>> On Fri, Jul 24, 2020 at 12:07:55PM -0700, sathyanarayanan.kuppuswamy@linux.intel.com wrote:
>>>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>>>>
>>>> Current pcie_do_recovery() implementation has following two issues:
>>>>
>>>
>>> I'm having trouble parsing this out, probably just lack of my
>>> understanding...
>>>
>>>> 1. Fatal (DPC) error recovery is currently broken for non-hotplug
>>>> capable devices. Current fatal error recovery implementation relies
>>>> on PCIe hotplug (pciehp) handler for detaching and re-enumerating
>>>> the affected devices/drivers. pciehp handler listens for DLLSC state
>>>> changes and handles device/driver detachment on DLLSC_LINK_DOWN event
>>>> and re-enumeration on DLLSC_LINK_UP event. So when dealing with
>>>> non-hotplug capable devices, recovery code does not restore the state
>>>> of the affected devices correctly.
>>>
>>> Apparently in the hotplug case, something *does* restore the state of
>>> affected devices?
>>
>> Yes, in hotplug case, DLLSC state change handler takes over detachment
>> /cleanup and re-attachment of affected devices/drivers.
> 
> Where does the restore happen here?  I.e., what function does this?

DLLSC link down event will remove affected devices/drivers. And link up event
will re-create all devices.

on DLLSC link down event
->pciehp_ist()
   ->pciehp_handle_presence_or_link_change()
     ->pciehp_disable_slot()
       ->__pciehp_disable_slot()
         ->remove_board()
           ->pciehp_unconfigure_device()

on DLLSC link up event
->pciehp_ist()
   ->pciehp_handle_presence_or_link_change()
     ->pciehp_enable_slot()
       ->__pciehp_enable_slot()
         ->board_added()
           ->pciehp_configure_device()

> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer