Re: [PATCH v12 0/6] Address error and recovery for AER and DPC

[poza@codeaurora.org]

On 2018-03-12 19:55, Keith Busch wrote:
> On Sun, Mar 11, 2018 at 11:03:58PM -0400, Sinan Kaya wrote:
>> On 3/11/2018 6:03 PM, Bjorn Helgaas wrote:
>> > On Wed, Feb 28, 2018 at 10:34:11PM +0530, Oza Pawandeep wrote:
>> 
>> > That difference has been there since the beginning of DPC, so it has
>> > nothing to do with *this* series EXCEPT for the fact that it really
>> > complicates the logic you're adding to reset_link() and
>> > broadcast_error_message().
>> >
>> > We ought to be able to simplify that somehow because the only real
>> > difference between AER and DPC should be that DPC automatically
>> > disables the link and AER does it in software.
>> 
>> I agree this should be possible. Code execution path should be almost
>> identical to fatal error case.
>> 
>> Is there any reason why you went to stop driver path, Keith?
> 
> The fact is the link is truly down during a DPC event. When the link
> is enabled again, you don't know at that point if the device(s) on the
> other side have changed. Calling a driver's error handler for the wrong
> device in an unknown state may have undefined results. Enumerating the
> slot from scratch should be safe, and will assign resources, tune bus
> settings, and bind to the matching driver.
> 
> Per spec, DPC is the recommended way for handling surprise removal
> events and even recommends DPC capable slots *not* set 'Surprise'
> in Slot Capabilities so that removals are always handled by DPC. This
> service driver was developed with that use in mind.

Now it begs the question, that

after DPC trigger

should we enumerate the devices, ?
or
error handling callbacks, followed by stop devices followed by 
enumeration ?
or
error handling callbacks, followed by enumeration ? (no stop devices)

Regards,
Oza.