Re: [PATCH] PCI: rockchip: check link status when validating device

[Brian Norris <briannorris@chromium.org>]

On Wed, May 24, 2017 at 09:14:52AM +0800, Shawn Lin wrote:
> 在 2017/5/24 9:00, Brian Norris 写道:
> >On Wed, May 24, 2017 at 08:54:14AM +0800, Shawn Lin wrote:
> >>The reason for me to added this check is that I saw a external abort
> >>down to rockchip_pcie_rd_own_conf, of which I highly suspected was that
> >>the link was re-init or total broken at that time.
> >
> >I've seen plenty of aborts in this function as well, but I've verified
> >that the link was still reported "up" in all the cases I could reproduce.
> >
> 
> I think it's reasonable as the link could be retrained automatically if
> it's not totaly broken at all. Did you poweroff the endpoint and could
> still pass this check?

I don't think I powered it off entirely, but I did try asserting its PD#
pin, which powers of most of the functionality -- enough that it
apparently causes aborts, but doesn't bring the link down.

> >So, do you "suspect" or did you "prove"? e.g., log cases where this
> >check actually helps?
> 
> I was powering off the devices and did a lspci, and saw the log cases
> there. I will check this again.
> 
> >
> >And to Bjorn's point: do you know *why* such cases were hit? That would
> >help to understand if the cases you're worrying about are hopelessly
> >racy, or if there's some way to ensure synchronization.

OK, so you've answered this question: losing power is hopelessly racy.

I guess it's up to Bjorn as to whether this racy check is useful at all
then.

Brian