[lkml]   [2020]   [May]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH v1 1/1] PCI/ERR: Handle fatal error recovery for non-hotplug capable devices

On 5/26/20 8:00 PM, Oliver O'Halloran wrote:
> On Wed, May 27, 2020 at 12:00 PM Kuppuswamy, Sathyanarayanan
> <> wrote:
>> Hi,
>> On 5/21/20 7:56 PM, Yicong Yang wrote:
>>> On 2020/5/22 3:31, Kuppuswamy, Sathyanarayanan wrote:
>>> Not exactly. In pci_bus_error_reset(), we call pci_slot_reset() only if it's
>>> hotpluggable. But we always call pci_bus_reset() to perform a secondary bus
>>> reset for the bridge. That's what I think is unnecessary for a normal link,
>>> and that's what reset link indicates us to do. The slot reset is introduced
>>> in the process only to solve side effects. (c4eed62a2143, PCI/ERR: Use slot reset if available)
>> IIUC, pci_bus_reset() will do slot reset if its supported (hot-plug
>> capable slots). If its not supported then it will attempt secondary
>> bus reset. So secondary bus reset will be attempted only if slot
>> reset is not supported.
>> Since reported_error_detected() requests us to do reset, we will have
>> to attempt some kind of reset before we call ->slot_reset() right?
> Yes, the driver returns PCI_ERS_RESULT_NEED_RESET from
> ->error_detected() to indicate that it doesn't know how to recover
> from the error. How that reset is performed doesn't really matter, but
> it does need to happen.
>>> PCI_ERS_RESULT_NEED_RESET indicates that the driver
>>> wants a platform-dependent slot reset and its ->slot_reset() method to be called then.
>>> I don't think it's same as slot reset mentioned above, which is only for hotpluggable
>>> ones.
>> What you think is the correct reset implementation ? Is it something
>> like this?
>> if (hotplug capable)
>> try_slot_reset()
>> else
>> do_nothing()
> Looks broken to me, but all the reset handling is a rat's nest so
> maybe I'm missing something. In the case of a DPC trip the link is
> disabled which has the side-effect of hot-resetting the downstream
> device. Maybe it's fine?
Yes, in case of DPC (Fatal errors) link is already reset. So we
don't need any special handling. This reset logic is mainly for
non-fatal errors.
> As an aside, why do we have both ->slot_reset() and ->reset_done() in
> the error handling callbacks? Seems like their roles are almost
> identical.
Not sure.I think reset_done() is final cleanup.
> Oliver

 \ /
  Last update: 2020-05-27 05:07    [W:0.085 / U:1.268 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site