Re: [net-next PATCH v1 1/7] Documentation: ACPI: DSD: Document MDIO PHY

[Grant Likely]

On 30/09/2020 17:37, Rafael J. Wysocki wrote:
> On Wed, Sep 30, 2020 at 6:05 PM Calvin Johnson
> <calvin.johnson@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> > ---
> >
> >   Documentation/firmware-guide/acpi/dsd/phy.rst | 78 +++++++++++++++++++
> >   1 file changed, 78 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..f10feb24ec1c
> > --- /dev/null
> > +++ b/Documentation/firmware-guide/acpi/dsd/phy.rst
> > @@ -0,0 +1,78 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +
> > +=========================
> > +MDIO bus and PHYs in ACPI
> > +=========================
> > +
> > +The PHYs on an mdiobus are probed and registered using
> > +fwnode_mdiobus_register_phy().
> > +Later, for connecting these PHYs to MAC, the PHYs registered on the
> > +mdiobus have to be referenced.
> > +
> > +phy-handle
> > +-----------
> > +For each MAC node, a property "phy-handle" is used to reference the
> > +PHY that is registered on an MDIO bus.
>
> It is not clear what "a property" means in this context.
>
> This should refer to the documents introducing the _DSD-based generic
> device properties rules, including the GUID used below.
>
> You need to say whether or not the property is mandatory and if it
> isn't mandatory, you need to say what the lack of it means.
>
> > +
> > +phy-mode
> > +--------
> > +Property "phy-mode" defines the type of PHY interface.
>
> This needs to be more detailed too, IMO.  At the very least, please
> list all of the possible values of it and document their meaning.

If the goal is to align with DT, it would be appropriate to point to 
where those properties are defined for DT rather than to have a separate 
description here. I suggest something along the lines of:

   The "phy-mode" _DSD property is used to describe the connection to
   the PHY. The valid values for "phy-mode" are defined in
   Documentation/devicetree/bindings/ethernet-controller.yaml

> > +
> > +An example of this is shown below::
> > +
> > +DSDT entry for MACs where PHY nodes are referenced
> > +--------------------------------------------------
> > +       Scope(\_SB.MCE0.PR17) // 1G
> > +       {
> > +         Name (_DSD, Package () {
> > +            ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
> > +                Package () {
> > +                    Package (2) {"phy-mode", "rgmii-id"},
> > +                    Package (2) {"phy-handle", Package (){\_SB.MDI0.PHY1}}
>
> What is "phy-handle"?
>
> You haven't introduced it above.

Can you elaborate? "phy-handle" has a section to itself in this 
document. Agree that it needs to be defined more, but it does read to me 
as having been defined.

> > +             }
> > +          })
> > +       }
> > +
> > +       Scope(\_SB.MCE0.PR18) // 1G
> > +       {
> > +         Name (_DSD, Package () {
> > +           ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
> > +               Package () {
> > +                   Package (2) {"phy-mode", "rgmii-id"},
> > +                   Package (2) {"phy-handle", Package (){\_SB.MDI0.PHY2}}
> > +           }
> > +         })
> > +       }
> > +
> > +DSDT entry for MDIO node
> > +------------------------
> > +a) Silicon Component
>
> What is this device, exactly?
>
> > +--------------------
> > +       Scope(_SB)
> > +       {
> > +         Device(MDI0) {
> > +           Name(_HID, "NXP0006")
> > +           Name(_CCA, 1)
> > +           Name(_UID, 0)
> > +           Name(_CRS, ResourceTemplate() {
> > +             Memory32Fixed(ReadWrite, MDI0_BASE, MDI_LEN)
> > +             Interrupt(ResourceConsumer, Level, ActiveHigh, Shared)
> > +              {
> > +                MDI0_IT
> > +              }
> > +           }) // end of _CRS for MDI0
> > +         } // end of MDI0
> > +       }
> > +
> > +b) Platform Component
> > +---------------------
> > +       Scope(\_SB.MDI0)
> > +       {
> > +         Device(PHY1) {
> > +           Name (_ADR, 0x1)
> > +         } // end of PHY1
> > +
> > +         Device(PHY2) {
> > +           Name (_ADR, 0x2)
> > +         } // end of PHY2
> > +       }
> > --
>
> What is the connection between the last two pieces of ASL and the _DSD
> definitions above?