linux-kernel - Re: [net-next PATCH v4 01/15] Documentation: ACPI: DSD: Document MDIO PHY

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Message-ID: <20210128131205.GA7882@lsv03152.swis.in-blr01.nxp.com>
Date:   Thu, 28 Jan 2021 18:42:05 +0530
From:   Calvin Johnson <calvin.johnson@....nxp.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Grant Likely <grant.likely@....com>,
        Jeremy Linton <jeremy.linton@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Cristi Sovaiala <cristian.sovaiala@....com>,
        Florin Laurentiu Chiculita <florinlaurentiu.chiculita@....com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Madalin Bucur <madalin.bucur@....nxp.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Pieter Jansen Van Vuuren <pieter.jansenvv@...boosystems.io>,
        Jon <jon@...id-run.com>, Saravana Kannan <saravanak@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        "linux.cj" <linux.cj@...il.com>,
        Diana Madalina Craciun <diana.craciun@....com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Len Brown <lenb@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [net-next PATCH v4 01/15] Documentation: ACPI: DSD: Document
 MDIO PHY

On Thu, Jan 28, 2021 at 01:00:40PM +0100, Rafael J. Wysocki wrote:
> On Thu, Jan 28, 2021 at 12:27 PM Calvin Johnson
> <calvin.johnson@....nxp.com> wrote:
> >
> > Hi Rafael,
> >
> > Thanks for the review. I'll work on all the comments.
> >
> > On Fri, Jan 22, 2021 at 08:22:21PM +0100, Rafael J. Wysocki wrote:
> > > On Fri, Jan 22, 2021 at 4:43 PM Calvin Johnson
> > > <calvin.johnson@....nxp.com> wrote:
> > > >
> > > > Introduce ACPI mechanism to get PHYs registered on a MDIO bus and
> > > > provide them to be connected to MAC.
> > > >
> > > > Describe properties "phy-handle" and "phy-mode".
> > > >
> > > > Signed-off-by: Calvin Johnson <calvin.johnson@....nxp.com>
> > > > ---
> > > >
> > > > Changes in v4:
> > > > - More cleanup
> > >
> > > This looks much better that the previous versions IMV, some nits below.
> > >
> > > > Changes in v3: None
> > > > Changes in v2:
> > > > - Updated with more description in document
> > > >
> > > >  Documentation/firmware-guide/acpi/dsd/phy.rst | 129 ++++++++++++++++++
> > > >  1 file changed, 129 insertions(+)
> > > >  create mode 100644 Documentation/firmware-guide/acpi/dsd/phy.rst
> > > >
> > > > diff --git a/Documentation/firmware-guide/acpi/dsd/phy.rst b/Documentation/firmware-guide/acpi/dsd/phy.rst
> > > > new file mode 100644
> > > > index 000000000000..76fca994bc99
> > > > --- /dev/null
> > > > +++ b/Documentation/firmware-guide/acpi/dsd/phy.rst
> > > > @@ -0,0 +1,129 @@
> > > > +.. SPDX-License-Identifier: GPL-2.0
> > > > +
> > > > +=========================
> > > > +MDIO bus and PHYs in ACPI
> > > > +=========================
> > > > +
> > > > +The PHYs on an MDIO bus [1] are probed and registered using
> > > > +fwnode_mdiobus_register_phy().
> > >
> > > Empty line here, please.
> > >
> > > > +Later, for connecting these PHYs to MAC, the PHYs registered on the
> > > > +MDIO bus have to be referenced.
> > > > +
> > > > +The UUID given below should be used as mentioned in the "Device Properties
> > > > +UUID For _DSD" [2] document.
> > > > +   - UUID: daffd814-6eba-4d8c-8a91-bc9bbf4aa301
> > >
> > > I would drop the above paragraph.
> > >
> > > > +
> > > > +This document introduces two _DSD properties that are to be used
> > > > +for PHYs on the MDIO bus.[3]
> > >
> > > I'd say "for connecting PHYs on the MDIO bus [3] to the MAC layer."
> > > above and add the following here:
> > >
> > > "These properties are defined in accordance with the "Device
> > > Properties UUID For _DSD" [2] document and the
> > > daffd814-6eba-4d8c-8a91-bc9bbf4aa301 UUID must be used in the Device
> > > Data Descriptors containing them."
> > >
> > > > +
> > > > +phy-handle
> > > > +----------
> > > > +For each MAC node, a device property "phy-handle" is used to reference
> > > > +the PHY that is registered on an MDIO bus. This is mandatory for
> > > > +network interfaces that have PHYs connected to MAC via MDIO bus.
> > > > +
> > > > +During the MDIO bus driver initialization, PHYs on this bus are probed
> > > > +using the _ADR object as shown below and are registered on the MDIO bus.
> > >
> > > Do you want to mention the "reg" property here?  I think it would be
> > > useful to do that.
> >
> > No. I think we should adhere to _ADR in MDIO case. The "reg" property for ACPI
> > may be useful for other use cases that Andy is aware of.
> 
> The code should reflect this, then.  I mean it sounds like you want to
> check the "reg" property only if this is a non-ACPI node.

Right. For MDIO case, that is what is required.
"reg" for DT and "_ADR" for ACPI.

However, Andy pointed out [1] that ACPI nodes can also hold reg property and
therefore, fwnode_get_id() need to be capable to handling that situation as
well.

Andy, any suggestion?

[1] https://lore.kernel.org/netdev/CAHp75Vef7Ln2hwx8BYao3SFxB8U2QTsfxPpxA_jxmujAMFpboA@mail.gmail.com/

Thanks
Calvin