Re: [PATCH net-next v1 3/4] dt-bindings: net: phy: add MaxLinear GPY2xx bindings

[Michael Walle]

Am 2022-12-05 22:53, schrieb Michael Walle:
> Am 2022-12-05 22:29, schrieb Rob Herring:
> > On Fri, Dec 02, 2022 at 04:12:03PM +0100, Michael Walle wrote:
> > > Add the device tree bindings for the MaxLinear GPY2xx PHYs.
> > >
> > > Signed-off-by: Michael Walle <michael@xxxxxxxx>
> > > ---
> > >
> > > Is the filename ok? I was unsure because that flag is only for the 
> > > GPY215
> > > for now. But it might also apply to others. Also there is no 
> > > compatible
> > > string, so..
> > >
> > >  .../bindings/net/maxlinear,gpy2xx.yaml        | 47 
> > > +++++++++++++++++++
> > >  1 file changed, 47 insertions(+)
> > >  create mode 100644 
> > > Documentation/devicetree/bindings/net/maxlinear,gpy2xx.yaml
> > >
> > > diff --git 
> > > a/Documentation/devicetree/bindings/net/maxlinear,gpy2xx.yaml 
> > > b/Documentation/devicetree/bindings/net/maxlinear,gpy2xx.yaml
> > > new file mode 100644
> > > index 000000000000..d71fa9de2b64
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/net/maxlinear,gpy2xx.yaml
> > > @@ -0,0 +1,47 @@
> > > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/net/maxlinear,gpy2xx.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: MaxLinear GPY2xx PHY
> > > +
> > > +maintainers:
> > > +  - Andrew Lunn <andrew@xxxxxxx>
> > > +  - Michael Walle <michael@xxxxxxxx>
> > > +
> > > +allOf:
> > > +  - $ref: ethernet-phy.yaml#
> > > +
> > > +properties:
> > > +  maxlinear,use-broken-interrupts:
> > > +    description: |
> > > +      Interrupts are broken on some GPY2xx PHYs in that they keep 
> > > the
> > > +      interrupt line asserted even after the interrupt status 
> > > register is
> > > +      cleared. Thus it is blocking the interrupt line which is 
> > > usually bad
> > > +      for shared lines. By default interrupts are disabled for this 
> > > PHY and
> > > +      polling mode is used. If one can live with the consequences, 
> > > this
> > > +      property can be used to enable interrupt handling.
> >
> > Just omit the interrupt property if you don't want interrupts and add 
> > it
> > if you do.
>
> How does that work together with "the device tree describes
> the hardware and not the configuration". The interrupt line
> is there, its just broken sometimes and thus it's disabled
> by default for these PHY revisions/firmwares. With this
> flag the user can say, "hey on this hardware it is not
> relevant because we don't have shared interrupts or because
> I know what I'm doing".

Specifically you can't do the following: Have the same device
tree and still being able to use it with a future PHY firmware
update/revision. Because according to your suggestion, this
won't have the interrupt property set. With this flag you can
have the following cases:
 (1) the interrupt information is there and can be used in the
     future by non-broken PHY revisions,
 (2) broken PHYs will ignore the interrupt line
 (3) except the system designer opts-in with this flag (because
     maybe this is the only PHY on the interrupt line etc).

-michael