netdev - Re: [PATCH] PCI: Add no-D3 quirk for Mellanox ConnectX-[45]

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Date:   Wed, 09 Jan 2019 16:09:02 +1100
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     David Gibson <david@...son.dropbear.id.au>,
        Leon Romanovsky <leon@...nel.org>, davem@...emloft.net,
        saeedm@...lanox.com, ogerlitz@...lanox.com, tariqt@...lanox.com,
        bhelgaas@...gle.com, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, netdev@...r.kernel.org,
        alex.williamson@...hat.com, linux-pci@...r.kernel.org,
        linux-rdma@...r.kernel.org, sbest@...hat.com, paulus@...ba.org,
        Alexey Kardashevskiy <aik@....ibm.com>
Subject: Re: [PATCH] PCI: Add no-D3 quirk for Mellanox ConnectX-[45]

On Mon, 2019-01-07 at 21:01 -0700, Jason Gunthorpe wrote:
> 
> > In a very cryptic way that requires manual parsing using non-public
> > docs sadly but yes. From the look of it, it's a completion timeout.
> > 
> > Looks to me like we don't get a response to a config space access
> > during the change of D state. I don't know if it's the write of the D3
> > state itself or the read back though (it's probably detected on the
> > read back or a subsequent read, but that doesn't tell me which specific
> > one failed).
> 
> If it is just one card doing it (again, check you have latest
> firmware) I wonder if it is a sketchy PCI-E electrical link that is
> causing a long re-training cycle? Can you tell if the PCI-E link is
> permanently gone or does it eventually return?

No, it's 100% reproducable on systems with that specific card model,
not card instance, and maybe different systems/cards as well, I'll let
David & Alexey comment further on that.

> Does the card work in Gen 3 when it starts? Is there any indication of
> PCI-E link errors?

Nope.

> Everytime or sometimes?
> 
> POWER 8 firmware is good? If the link does eventually come back, is
> the POWER8's D3 resumption timeout long enough?
> 
> If this doesn't lead to an obvious conclusion you'll probably need to
> connect to IBM's Mellanox support team to get more information from
> the card side.

We are IBM :-) So far, it seems to be that the card is doing something
not quite right, but we don't know what. We might need to engage
Mellanox themselves.

Cheers,
Ben.