linux-kernel - Re: [PATCH v3 net-next 12/14] dt-bindings: net: dsa: ocelot: add ocelot-ext documentation

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Date:   Wed, 5 Oct 2022 08:44:08 -0700
From:   Colin Foster <colin.foster@...advantage.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, netdev@...r.kernel.org,
        Russell King <linux@...linux.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        UNGLinuxDriver@...rochip.com,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Lee Jones <lee@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Vladimir Oltean <olteanv@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH v3 net-next 12/14] dt-bindings: net: dsa: ocelot: add
 ocelot-ext documentation

On Wed, Oct 05, 2022 at 10:03:04AM +0200, Krzysztof Kozlowski wrote:
> On 05/10/2022 02:08, Colin Foster wrote:
> > Hi Krzysztof,
> > 
> > On Tue, Oct 04, 2022 at 01:19:33PM +0200, Krzysztof Kozlowski wrote:
> >> On 26/09/2022 02:29, Colin Foster wrote:
> >>> The ocelot-ext driver is another sub-device of the Ocelot / Felix driver
> >>> system, which currently supports the four internal copper phys.
> >>>
> >>> Signed-off-by: Colin Foster <colin.foster@...advantage.com>
> > ...
> >>> +  # Ocelot-ext VSC7512
> >>> +  - |
> >>> +    spi {
> >>> +        soc@0 {
> >>
> >> soc in spi is a bit confusing.
> >>
> >> Does it even pass the tests? You have unit address but no reg.
> > 
> > I omitted those from the documentation. Rob's bot is usually quick to
> > alert me when I forgot to run dt_binding_check and something fails
> > though. I'll double check, but I thought everything passed.
> > 
> >>
> >>> +            compatible = "mscc,vsc7512";
> >>
> >>
> >>> +            #address-cells = <1>;
> >>> +            #size-cells = <1>;
> >>> +
> >>> +            ethernet-switch@0 {
> >>> +                compatible = "mscc,vsc7512-switch";
> >>> +                reg = <0 0>;
> >>
> >> 0 is the address on which soc bus?
> > 
> > This one Vladimir brought up as well. The MIPS cousin of this chip
> > is the VSC7514. They have exactly (or almost exactly) the same hardware,
> > except the 7514 has an internal MIPS while the 7512 has an 8051.
> > 
> > Both chips can be controlled externally via SPI or PCIe. This is adding
> > control for the chip via SPI.
> > 
> > For the 7514, you can see there's an array of 20 register ranges that
> > all get mmap'd to 20 different regmaps.
> > 
> > (Documentation/devicetree/bindings/net/mscc,vsc7514-switch.yaml)
> > 
> >     switch@...0000 {
> >       compatible = "mscc,vsc7514-switch";
> >       reg = <0x1010000 0x10000>,
> >             <0x1030000 0x10000>,
> >             <0x1080000 0x100>,
> >             <0x10e0000 0x10000>,
> >             <0x11e0000 0x100>,
> >             <0x11f0000 0x100>,
> >             <0x1200000 0x100>,
> >             <0x1210000 0x100>,
> >             <0x1220000 0x100>,
> >             <0x1230000 0x100>,
> >             <0x1240000 0x100>,
> >             <0x1250000 0x100>,
> >             <0x1260000 0x100>,
> >             <0x1270000 0x100>,
> >             <0x1280000 0x100>,
> >             <0x1800000 0x80000>,
> >             <0x1880000 0x10000>,
> >             <0x1040000 0x10000>,
> >             <0x1050000 0x10000>,
> >             <0x1060000 0x10000>,
> >             <0x1a0 0x1c4>;
> >       reg-names = "sys", "rew", "qs", "ptp", "port0", "port1",
> >             "port2", "port3", "port4", "port5", "port6",
> >             "port7", "port8", "port9", "port10", "qsys",
> >             "ana", "s0", "s1", "s2", "fdma";
> > 
> > 
> > The suggestion was to keep the device trees of the 7512 and 7514 as
> > similar as possible, so this will essentially become:
> >     switch@...10000 {
> >       compatible = "mscc,vsc7512-switch";
> >       reg = <0x71010000 0x10000>,
> >             <0x71030000 0x10000>,
> >       ...
> 
> I don't understand how your answer relates to "reg=<0 0>;". How is it
> going to become 0x71010000 if there is no other reg/ranges set in parent
> nodes. The node has only one IO address, but you say the switch has 20
> addresses...
> 
> Are we talking about same hardware?

Yes. The switch driver for both the VSC7512 and VSC7514 use up to ~20 regmaps
depending on what capabilities it is to have. In the 7514 they are all
memory-mapped from the device tree. While the 7512 does need these
regmaps, they are managed by the MFD, not the device tree. So there
isn't a _need_ for them to be here, since at the end of the day they're
ignored.

The "reg=<0 0>;" was my attempt to indicate that they are ignored, but I
understand that isn't desired. So moving forward I'll add all the
regmaps back into the device tree.

> 
> Best regards,
> Krzysztof
>