linux-kernel - Re: [PATCH 1/1] net: dsa: rtl8366rb: standardize init jam tables

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Date:   Tue, 26 Jan 2021 22:40:39 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Lorenzo Carletti <lorenzo.carletti98@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] net: dsa: rtl8366rb: standardize init jam tables

On Tue, Jan 26, 2021 at 10:08 PM Vladimir Oltean <olteanv@...il.com> wrote:
> On Mon, Jan 25, 2021 at 05:56:31AM +0100, Lorenzo Carletti wrote:

> > In the rtl8366rb driver there are some jam tables which contain
> > undocumented values.
> > While trying to understand what these tables actually do,
> > I noticed a discrepancy in how one of those was treated.
>
> And did you manage to find out what these tables actually do?

I think Lorenzo mentioned that he found some settings in there,
I don't know if it was anything substantial though?

I put Lorenzon on track to investigate the driver, we thought
it could be an 8051 CPU so that some of the arrays could
be decoded into 8051 instructions, but so far we didn't get
anywhere with it.

The background was some mumble on the internet on
8051 in RTL8366 switches:
https://news.ycombinator.com/item?id=21040488
https://web.archive.org/web/20190922094616if_/https://twitter.com/whitequark/status/1175701730819895296

> > Most of them were plain u16 arrays, while the ethernet one was
> > an u16 matrix.
> > By looking at the vendor's droplets of source code these tables came from,
> > I found out that they were all originally u16 matrixes.
> >
> > This commit standardizes the jam tables, turning them all into
> > u16 matrixes.
>
> Why? What difference does it make?

I think it's nice that the format is the same on all tables.

Yours,
Linus Walleij