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SubjectRe: [PATCH net] net: mvpp2: Enable autoneg bypass for 1000BaseX/2500BaseX ports
On Fri, 29 May 2020 16:59:28 +0200
Andrew Lunn <andrew@lunn.ch> wrote:

> On Fri, May 29, 2020 at 01:05:39PM +0200, Thomas Bogendoerfer wrote:
> > On Thu, 28 May 2020 23:04:20 +0100
> > Russell King - ARM Linux admin <linux@armlinux.org.uk> wrote:
> >
> > > Can you explain this please? Just as we think we understand what's
> > > going on here, you throw in a new comment that makes us confused.
> >
> > sorry about that.
> >
> > > You said previously that the mvpp2 was connected to a switch, which
> > > makes us think that you've got some DSA-like setup going on here.
> > > Does your switch drop its serdes link when all the external links
> > > (presumably the 10G SFP+ cages) fail?
> > >
> > > Both Andrew and myself wish to have a complete picture before we
> > > move forward with this.
> >
> > full understandable, I'll try by a small picture, which just
> > covers one switch:
> >
> > external ports
> > | | | |
> > *-----------------------------*
> > | 1 1 2 2 |
> > | |
> > | switch |
> > | |
> > | 1 2 1 2 |
> > *-----------------------------*
> > | | | |
> > | | | |
> > *----------* *----------*
> > | 1 2 | | 1 2 |
> > | | | |
> > | node 1 | ... | node 8 |
> > | | | |
> > *----------* *----------*
> >
> > External ports a grouped in ports to network 1 and network 2. If one of the
> > external ports has an established link, this link state will be propagated
> > to the internal ports. Same when both external ports of a network are down.
>
> By propagated, you mean if the external link is down, the link between
> the switch and node 1 will also be forced down, at the SERDES level?

yes

> And if external ports are down, the nodes cannot talk to each other?

correct

> External link down causes the whole in box network to fall apart? That
> seems a rather odd design.

as I'm not an expert in ceph, I can't judge. But I'll bring it up.

> > I have no control over the software running on the switch, therefore I can't
> > enable autoneg on the internal links.
>
> O.K. So that means using in-band signalling in DT is clearly
> wrong. There is no signalling....
>
> What you are actually interested in is the sync state of the SERDES?
> The link is up if the SERDES has sync.

yes, that's what I need. How can I do that ?

Thomas.

--
SUSE Software Solutions Germany GmbH
HRB 36809 (AG Nürnberg)
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