linux-kernel - Re: [PATCH 3/3] net: microchip_t1s: conditional collision detection

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Message-ID: <ZWWwYz0w5-ti78QI@debian>
Date:   Tue, 28 Nov 2023 10:18:27 +0100
From:   Ramón Nordin Rodriguez 
        <ramon.nordin.rodriguez@...roamp.se>
To:     Parthiban.Veerasooran@...rochip.com
Cc:     andrew@...n.ch, hkallweit1@...il.com, linux@...linux.org.uk,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] net: microchip_t1s: conditional collision detection

> > 
> > But the change was dropped in that patchset right? It's not present in
> > netdev-next.
> Yes, it was dropped. The reason why I gave this info is, you mentioned 
> in the cover letter that it took some time for you to find this in the 
> datasheet.

Ha, sometimes I have bad luck while thinking. I guess I never understood
that change and subsequently forgot about it.

> > 
> >> As it is recommended to do it in a separate patch and also the
> >> datasheets of LAN867X Rev.B1 and LAN865X Rev.B0 internal PHY have these
> >> register is reserved, we were working for a feasible solution to
> >> describe this for customer and mainline. By the time many other things
> >> messed up and couldn't reach the mainline on time.
> >>
> > 
> > Far as I can tell 'collision detect' is described in the following
> > sections of respective datasheet:
> > 
> > * 11.5.51 - LAN8650
> > * 5.4.48  - LAN8670
> > 
> > The rest of the bits are reserved though. The change I propose only
> > manipulate the documented (bit 15) collision bit.
> > 
> > Is your point that the lan8670 datasheet is only valid for rev.c and not
> > rev.b?
> It is valid for rev.b1 as well but the current datasheet for rev.c1 
> doesn't show that info.

Thank you for clearing that up! So if I get you correctly this change
would in fact be correct for both lan867x rev.b and rev.c.

> > 
> > Andrew suggested on the cover letter that it be interesting to look at
> > completly disabling collision detect, any strings you can pull at
> > Microchip to investigate that?
> Unfortunately I can't commit anything from my side as we are occupied 
> with other activities. But definitely I will try my level best if time 
> permits. Alternatively you can contact our Microchip customer support 
> team if you are interested to do this testing at Microchip.

I get that, might do as you suggest.

> > Also any input on my suggested testing methodology is more than welcome.
> > 
> >> We also implemented LAN867X Rev.C1 support already in the driver and
> >> published in our product site and in the process of preparing mainline
> >> patches. But unfortunately it took little more time to make it.
> >>
> >> https://ww1.microchip.com/downloads/aemDocuments/documents/AIS/ProductDocuments/CodeExamples/EVB-LAN8670-USB_Linux_Driver_1v0.zip
> > 
> > I'm aware, we've been using a derivative of that work at ferroamp for
> > development. But it's been driving me nuts, being the 't1s guy' at work,
> > and maintaining out of tree drivers for weird dev boxes.
> > 
> > It's not my intention to beat you to the punch, I just want a mainlined
> > driver so that I can spend less of my time on plumbing.
> I completely understand. Also it was not my intention too. Just to let 
> you know why it is delayed in reaching mainline and a quick reference 
> for the existing implementation. Enjoy!

I get that, in an ideal world FOSS would be the top prio for all
industry actors. I'm lucky enough to get some time reserved for it.

R