Re: git: a58536b91ae3 - main - pci: Disable Electromechanical Interlock.

From: John Baldwin <>
Date: Tue, 04 Oct 2022 16:47:04 UTC
On 10/4/22 7:44 AM, Alexander Motin wrote:
> The branch main has been updated by mav:
> URL:
> commit a58536b91ae3931d222c3e4f1a949ff4a4927fb2
> Author:     Alexander Motin <>
> AuthorDate: 2022-10-04 14:34:15 +0000
> Commit:     Alexander Motin <>
> CommitDate: 2022-10-04 14:34:15 +0000
>      pci: Disable Electromechanical Interlock.
>      Add sysctl/tunable to control Electromechanical Interlock support.
>      Disable it by default since Linux does not do it either and it seems
>      the number of systems having it broken is higher than having working.
>      This fixes NVMe backplane operation on ASUS RS500A-E11-RS12U server
>      with AMD EPYC 7402 CPU, where attempts to control reported interlock
>      for some reason end up in PCIe link loss, while interlock status does
>      not change (it is not really there).
>      MFC after:      2 weeks

See also, though
that is more for the case where slots aren't really hotplug at all.

The root issue seems to be that there are generic HotPlug-capable
bridges but that manufacturers fail to correctly wire up the various
input pins such that the bridges can actually determine that there is no
MRL or EI, etc.  The above PR (which I still can't get the reporter to
test the patch for, but perhaps should just merge?) disables PCI-e hotplug
if the link is up, but the other status bits claim that the device is
partially inserted when attaching the bridge.

John Baldwin