netdev - Re: [PATCH 2/4] dt-bindings: net: dsa: document internal MDIO bus

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Date: Wed, 13 Sep 2023 10:42:31 +0300
From: Vladimir Oltean <olteanv@...il.com>
To: Arınç ÜNAL <arinc.unal@...nc9.com>
Cc: Andrew Lunn <andrew@...n.ch>, Florian Fainelli <f.fainelli@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Woojung Huh <woojung.huh@...rochip.com>,
	UNGLinuxDriver@...rochip.com,
	Linus Walleij <linus.walleij@...aro.org>,
	Alvin Šipraga <alsi@...g-olufsen.dk>,
	Daniel Golle <daniel@...rotopia.org>,
	Landen Chao <Landen.Chao@...iatek.com>,
	DENG Qingfang <dqfext@...il.com>,
	Sean Wang <sean.wang@...iatek.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	mithat.guner@...ont.com, erkin.bozoglu@...ont.com,
	netdev@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 2/4] dt-bindings: net: dsa: document internal MDIO bus

On Wed, Sep 13, 2023 at 08:52:37AM +0300, Arınç ÜNAL wrote:
> On 12.09.2023 22:34, Vladimir Oltean wrote:
> > On Tue, Sep 12, 2023 at 10:23:51PM +0300, Arınç ÜNAL wrote:
> > > The phylink bindings for user ports I ended up making by looking up the
> > > existing devicetrees are different than the phylink bindings for the shared
> > > (CPU and DSA) ports currently enforced on all switches.
> > > 
> > > My phylink bindings for user ports:
> > > 
> > >              allOf:
> > >                - anyOf:
> > >                    - required: [ fixed-link ]
> > >                    - required: [ phy-handle ]
> > >                    - required: [ managed ]
> > > 
> > >                - if:
> > >                    required: [ fixed-link ]
> > >                  then:
> > >                    not:
> > >                      required: [ managed ]
> > 
> > Right, it should have been anyOf and not oneOf.. my mistake. It is a bug
> > which should be fixed. It's the same phylink that gets used in both cases,
> > user ports and shared ports :)
> 
> One more thing, I don't recall phy-mode being required to be defined for
> user ports as it will default to GMII. I don't believe this is the same
> case for shared ports so phy-mode is required only for them?

phy-mode is not strictly required, but I think there is a strong
preference to set it. IIRC, when looking at the DSA device trees, there
was no case where phy-mode would be absent on CPU/DSA ports if the other
link properties were also present, so we required it too. There were no
complaints in 1 year since dsa_shared_port_validate_of() is there. The
requirement can be relaxed to just a warning and no error in the kernel,
and the removal of "required" in the schema, if it helps making it
common with user ports.

I think that the fallback to PHY_INTERFACE_MODE_GMII applies only if
there is a phy_device (phy-handle). But otherwise, I don't remember if
the PHY_INTERFACE_MODE_NA passed to phylink_create() will persist at
runtime, or cause an error somewhere.

> > > The phylink bindings for shared ports enforced on all switches on
> > > dsa-port.yaml:
> > > 
> > >    allOf:
> > >      - required:
> > >          - phy-mode
> > >      - oneOf:
> > >          - required:
> > >              - fixed-link
> > >          - required:
> > >              - phy-handle
> > >          - required:
> > >              - managed
> > > 
> > > Here's what I understand:
> > > 
> > > - For switches in dsa_switches_apply_workarounds[]
> > >    - Enforce the latter for shared ports.
> > >    - Enforce the former for user ports.
> > > 
> > > - For switches not in dsa_switches_apply_workarounds[]
> > >    - Enforce the former for all ports.
> > 
> > No, no. We enforce the dt-schema regardless of switch presence in
> > dsa_switches_apply_workarounds[], to encourage users to fix device trees
> > (those who run schema validation). The kernel workaround consists in
> > doing something (skipping phylink) for the device trees where the schema
> > warns on shared ports. But there should be a single sub-schema for
> > validating phylink bindings, whatever port kind it is.
> 
> Hmm, like writing phylink.yaml and then referring to it under the port
> pattern node? This could prevent a lot of repetition.
> 
> Arınç

Yes, that would sound good.