Date: Fri, 21 Jun 2024 13:04:43 -0500
From: Andrew Halaney <ahalaney@...hat.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Andrew Lunn <andrew@...n.ch>, Bartosz Golaszewski <brgl@...ev.pl>, 
	Vinod Koul <vkoul@...nel.org>, Alexandre Torgue <alexandre.torgue@...s.st.com>, 
	Jose Abreu <joabreu@...opsys.com>, "David S . Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Maxime Coquelin <mcoquelin.stm32@...il.com>, 
	Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
	linux-stm32@...md-mailman.stormreply.com, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH net-next 1/8] net: phy: add support for overclocked SGMII

On Thu, Jun 20, 2024 at 02:42:41PM GMT, Andrew Halaney wrote:
> On Wed, Jun 19, 2024 at 10:07:21PM GMT, Russell King (Oracle) wrote:
> > On Wed, Jun 19, 2024 at 09:51:12PM +0200, Andrew Lunn wrote:
> > > phylib supports out of band signalling, which is enough to make this
> > > work, so long as two peers will actually establish a link because they
> > > are sufficiently tolerant of what the other end is doing. Sometimes
> > > they need a hint. Russell King has been working on this mess, and i'm
> > > sure he will be along soon.
> > 
> > ... and I'm rolling my eyes, wondering whether I will get time to
> > finish the code that I started any time soon. I'll note that the more
> > hacky code we end up merging, the harder it will become to solve this
> > problem (and we already have several differing behaviours merged with
> > 2500base-X already.)
> > 
> > > What i expect will happen is you keep calling this 2500BaseX, without
> > > in band signalling. You can look back in the netdev mailling list for
> > > more details and those that have been here before you. It is always
> > > good to search the history, otherwise you are just going to repeat it.
> > 
> > That's where things start getting sticky, because at the moment,
> > phylink expects 2500base-X to be like 1000base-X, and be a media
> > interface mode rather than a MAC-to-PHY interface mode. This is partly
> > what my patches will address if I can get around to finishing them -
> > but at this point I really do not know when that will be.
> > 
> > I still have the high priority work problem that I'm actively involved
> > with. I may have three weeks holiday at the start of July (and I really
> > need it right now!) Then, there's possibly quite a lot of down time in
> > August because I'm having early cataract ops which will substantially
> > change my eye sight. There's two possible outcomes from that. The best
> > case is that in just over two weeks after the first op, I'll be able to
> > read the screen without glasses. The worst case is that I have to wait
> > a further two to three weeks to see my optometrist (assuming he has
> > availability), and then wait for replacement lenses to be made up,
> > fitted and the new glasses sent.
> > 
> > So, I'm only finding the occasional time to be able to look at
> > mainline stuff, and I don't see that changing very much until maybe
> > September.
> > 
> > At this point, I think we may as well give up and let people do
> > whatever they want to do with 2500base-X (which is basically what we're
> > already doing), and when they have compatibility problems... well...
> > really not much we can do about that, and it will be way too late to
> > try and sort the mess out.
> 
> I hope your holiday and operation go well Russell.
> 
> Pardon my ignorance, but I know of quite a few things you have in flight
> and because of that I'm not entirely sure what specific patches you're
> referring to above. Have those hit the list? I know you're cleaning
> up stmmac's phylink/pcs usage, but I'm thinking that this is outside of
> that series. Thanks in advance for helping me understand all that's in
> progress around this mess of a topic!

Nevermind my question, I was talking a little about this today with respect to a
Renesas board as well (can't escape it it seems) and in going through
our convos I found: https://lore.kernel.org/netdev/ZlNi11AsdDpKM6AM@shell.armlinux.org.uk/

    """
    I do have some work-in-progress patches that attempt to sort this out
    in phylink and identify incompatible situations.

    See http://git.armlinux.org.uk/cgit/linux-arm.git/log/?h=net-queue

    commits (I think)...

    net: phylink: clean up phylink_resolve()

    to:

    net: phylink: switch to MLO_AN_PHY when PCS uses outband

    and since I'm converting stmmac's hacky PCS that bypasses phylink to
    a real phylink_pcs, the ethqos code as it stands presents a blocker
    because of this issue. So, I'm intending to post a series in the next
    few days (after the bank holiday) and will definitely need to be
    tested on ethqos hardware.
    """

Thanks,
Andrew

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