On 2018-08-21 20:07, Keith Busch wrote:
On Tue, Aug 21, 2018 at 04:06:30PM +1000, Benjamin Herrenschmidt wrote:
On Tue, 2018-08-21 at 10:44 +0530, poza@xxxxxxxxxxxxxx wrote:
>
> Ok Let me summarize the so far discussed things.
>
> It would be nice if we all (Bjorn, Keith, Ben, Sinan) can hold consensus
> on this.
>
> 1) Right now AER and DPC both calls pcie_do_fatal_recovery(), I majorly
> see DPC as error handling and recovery agent rather than being used for
> hotplug.
> so in my opinion, both AER and DPC should have same error handling
> and recovery mechanism
Yes.
> so if there is a way to figure out that in absence of pcihp, if DPC
> is being used to support hotplug then we fall back to original DPC
> mechanism (which is remove devices)
Not exactly. If the presence detect change indicates it was a hotplug
event rather.
The actions associated with error recovery will trigger link state
changes
for a lot of existing hardware. PCIEHP currently does the same removal
sequence for both link state change (DLLSC) and presence detect change
(PDC) events.
It sounds like you want pciehp to do nothing on the DLLSC events that
it
currently handles, and instead do the board removal only on PDC. If
that
is the case, is the desire to not remove devices downstream a
permanently
disabled link, or does that responsibility fall onto some other
component?
Keith
Are you in agreement with following ?
"
Right now AER and DPC both calls pcie_do_fatal_recovery(), I majorly see
DPC as error handling and recovery agent rather than being used for
hotplug.
so in my opinion, both AER and DPC should have same error handling
and recovery mechanism
so if there is a way to figure out that in absence of pcihp, if DPC
is being used to support hotplug then we fall back to original DPC
mechanism (which is remove devices)
otherwise, we fall back to drivers callbacks.
Spec 6.7.5 Async Removal
"
The Surprise Down error resulting from async removal may trigger
Downstream Port Containment (See Section 6.2.10).
Downstream Port Containment following an async removal may be
utilized to hold the Link of a
Downstream Port in the Disabled LTSSM state while host software
recovers from the side effects of an async removal.
"
I think above is implementation specific. but there has to be some
way to kow if we are using DPC for hotplug or not !
otherwise it is assumed to be used for error handling and recovery
pcie_do_fatal_recovery should take care of above. so that we support
both error handling and async removal from DPC point of view.
"
