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

  Add the device tree bindings for the MaxLinear GPY2xx PHYs.

Signed-off-by: Michael Walle <michael@walle.cc>
---

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
  

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@walle.cc>
> ---
> 
> 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@lunn.ch>
> +  - Michael Walle <michael@walle.cc>
> +
> +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.
> +
> +      Affected PHYs (as far as known) are GPY215B and GPY215C.
> +    type: boolean
> +
> +dependencies:
> +  maxlinear,use-broken-interrupts: [ interrupts ]
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    ethernet {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        ethernet-phy@0 {
> +            reg = <0>;
> +            interrupts-extended = <&intc 0>;
> +            maxlinear,use-broken-interrupts;
> +        };
> +    };

I'm wondering if we want this in the example. We probably don't want
people to use this property by accident, i.e. copy/paste without
reading the rest of the document. This will becomes a bigger problem
if more properties are added, RGMII delays etc.

So maybe just skip the example?

   Andrew
  

Am 2022-12-02 19:31, schrieb Andrew Lunn:
> 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@walle.cc>
>> ---
>> 
>> 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@lunn.ch>
>> +  - Michael Walle <michael@walle.cc>
>> +
>> +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.
>> +
>> +      Affected PHYs (as far as known) are GPY215B and GPY215C.
>> +    type: boolean
>> +
>> +dependencies:
>> +  maxlinear,use-broken-interrupts: [ interrupts ]
>> +
>> +unevaluatedProperties: false
>> +
>> +examples:
>> +  - |
>> +    ethernet {
>> +        #address-cells = <1>;
>> +        #size-cells = <0>;
>> +
>> +        ethernet-phy@0 {
>> +            reg = <0>;
>> +            interrupts-extended = <&intc 0>;
>> +            maxlinear,use-broken-interrupts;
>> +        };
>> +    };
> 
> I'm wondering if we want this in the example. We probably don't want
> people to use this property by accident, i.e. copy/paste without
> reading the rest of the document. This will becomes a bigger problem
> if more properties are added, RGMII delays etc.
> 
> So maybe just skip the example?

I agree. Let's wait what the device tree maintainers say.

-michael
  

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@walle.cc>
> ---
> 
> 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@lunn.ch>
> +  - Michael Walle <michael@walle.cc>
> +
> +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.

> +
> +      Affected PHYs (as far as known) are GPY215B and GPY215C.
> +    type: boolean
> +
> +dependencies:
> +  maxlinear,use-broken-interrupts: [ interrupts ]
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    ethernet {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        ethernet-phy@0 {
> +            reg = <0>;
> +            interrupts-extended = <&intc 0>;
> +            maxlinear,use-broken-interrupts;

This is never actually checked by be schema because there is nothing to 
match on. If you want custom properties, then you need a compatible. 

> +        };
> +    };
> +
> +...
> -- 
> 2.30.2
> 
>
  

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@walle.cc>
>> ---
>> 
>> 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@lunn.ch>
>> +  - Michael Walle <michael@walle.cc>
>> +
>> +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".

>> +
>> +      Affected PHYs (as far as known) are GPY215B and GPY215C.
>> +    type: boolean
>> +
>> +dependencies:
>> +  maxlinear,use-broken-interrupts: [ interrupts ]
>> +
>> +unevaluatedProperties: false
>> +
>> +examples:
>> +  - |
>> +    ethernet {
>> +        #address-cells = <1>;
>> +        #size-cells = <0>;
>> +
>> +        ethernet-phy@0 {
>> +            reg = <0>;
>> +            interrupts-extended = <&intc 0>;
>> +            maxlinear,use-broken-interrupts;
> 
> This is never actually checked by be schema because there is nothing to
> match on. If you want custom properties, then you need a compatible.

This seems to be a problem for any phy bindings then.

-michael
  

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@walle.cc>
>>> ---
>>> 
>>> 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@lunn.ch>
>>> +  - Michael Walle <michael@walle.cc>
>>> +
>>> +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
  

On 06/12/2022 09:29, Michael Walle wrote:
> 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@walle.cc>
>>>> ---
>>>>
>>>> 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@lunn.ch>
>>>> +  - Michael Walle <michael@walle.cc>
>>>> +
>>>> +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".

Yeah, that's a good question. In your case broken interrupts could be
understood the same as "not connected", so property not present. When
things are broken, you do not describe them fully in DTS for the
completeness of hardware description, right?

> 
> 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).

I am not sure if I understand the case. You want to have a DTS with
interrupts and "maxlinear,use-broken-interrupts", where the latter will
be ignored by some future firmware? Isn't then the property not really
correct? Broken for one firmware on the same device, working for other
firmware on the same device?

I would assume that in such cases you (or bootloader or overlay) should
patch the DTS...



Best regards,
Krzysztof
  

Am 2022-12-06 09:38, schrieb Krzysztof Kozlowski:

>>>> 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".
> 
> Yeah, that's a good question. In your case broken interrupts could be
> understood the same as "not connected", so property not present. When
> things are broken, you do not describe them fully in DTS for the
> completeness of hardware description, right?

I'd agree here, but in this case it's different. First, it isn't
obvious in the first place that things are broken and boards in
the field wouldn't/couldn't get that update. I'd really expect
an erratum from MaxLinear here. And secondly, (which I
just noticed right now, sorry), is that the interrupt line
is also used for wake-on-lan, which can also be used even for
the "broken" PHYs.

To work around this, the basic idea was to just disable the
normal interrupts and fall back to polling mode, as the PHY
driver just use it for link detection and don't offer any
advanced features like PTP (for now). But still get the system
integrator a knob to opt-in to the old behavior on new device
trees.

>> 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).
> 
> I am not sure if I understand the case. You want to have a DTS with
> interrupts and "maxlinear,use-broken-interrupts", where the latter will
> be ignored by some future firmware?

Yes, that's correct.

> Isn't then the property not really correct? Broken for one firmware
> on the same device, working for other firmware on the same device?

Arguable, but you can interpret "use broken-interrupts" as no-op
if there are no broken interrupts.

> I would assume that in such cases you (or bootloader or overlay)
> should patch the DTS...

I think this would turn the opt-in into an opt-out and we'd rely
on the bootloader to workaround the erratum. Which isn't what we
want here.

-michael
  

Am 2022-12-06 10:44, schrieb Michael Walle:
> Am 2022-12-06 09:38, schrieb Krzysztof Kozlowski:
> 
>>>>> 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".
>> 
>> Yeah, that's a good question. In your case broken interrupts could be
>> understood the same as "not connected", so property not present. When
>> things are broken, you do not describe them fully in DTS for the
>> completeness of hardware description, right?
> 
> I'd agree here, but in this case it's different. First, it isn't
> obvious in the first place that things are broken and boards in
> the field wouldn't/couldn't get that update. I'd really expect
> an erratum from MaxLinear here. And secondly, (which I
> just noticed right now, sorry), is that the interrupt line
> is also used for wake-on-lan, which can also be used even for
> the "broken" PHYs.
> 
> To work around this, the basic idea was to just disable the
> normal interrupts and fall back to polling mode, as the PHY
> driver just use it for link detection and don't offer any
> advanced features like PTP (for now). But still get the system
> integrator a knob to opt-in to the old behavior on new device
> trees.
> 
>>> 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).
>> 
>> I am not sure if I understand the case. You want to have a DTS with
>> interrupts and "maxlinear,use-broken-interrupts", where the latter 
>> will
>> be ignored by some future firmware?
> 
> Yes, that's correct.
> 
>> Isn't then the property not really correct? Broken for one firmware
>> on the same device, working for other firmware on the same device?
> 
> Arguable, but you can interpret "use broken-interrupts" as no-op
> if there are no broken interrupts.
> 
>> I would assume that in such cases you (or bootloader or overlay)
>> should patch the DTS...
> 
> I think this would turn the opt-in into an opt-out and we'd rely
> on the bootloader to workaround the erratum. Which isn't what we
> want here.

Just a recap what happened on IRC:
  (1) Krzysztof signalled that such a property might be ok but the
      commit message should be explain it better. For reference
      here is what I explained there:

       maybe that property has a wrong name, but ultimately, it's just
       a hint that the systems designer wants to use the interrupts
       even if they don't work as expected, because they work on that
       particular hardware.
       the interrupt line is there but it's broken, there are device
       trees out there with that property, so all we can do is to not
       use the interrupts for that PHY. but as a systems designer who
       is aware of the consequences and knowing that they don't apply
       to my board, how could i then tell the driver to use it anyway.

  (2) Krzysztof pointed out that there is still the issue raised by
      Rob, that the schemas haven't any compatible and cannot be
      validated. I think that applies to all the network PHY bindings
      in the tree right now. I don't know how to fix them.

  (3) The main problem with the broken interrupt handling of the PHY
      is that it will disturb other devices on that interrupt line.
      IOW if the interrupt line is shared the PHY should fall back
      to polling mode. I haven't found anything in the interrupt
      subsys to query if a line is shared and I guess it's also
      conceptually impossible to do such a thing, because there
      might be any driver probed at a later time which also uses
      that line.
      Rob had the idea to walk the device tree and determine if
      a particular interrupt is used by other devices, too. If
      feasable, this sounds like a good enough heuristic for our
      problem. Although there might be some edge cases, like
      DT overlays loaded at linux runtime (?!).

So this is what I'd do now: I'd skip a new device tree property
for now and determine if the interrupt line is shared (by solely
looking at the DT) and then disable the interrupt in the PHY
driver. This begs the question what we do if there is no DT,
interrupts disabled or enabled?

Andrew, what do you think?

-michael
  

>  (2) Krzysztof pointed out that there is still the issue raised by
>      Rob, that the schemas haven't any compatible and cannot be
>      validated. I think that applies to all the network PHY bindings
>      in the tree right now. I don't know how to fix them.

i've been offline for a while, i sabotaged my own mail server...

You can always add an unneeded compatible, using the PHY devices ID:

      - pattern: "^ethernet-phy-id[a-f0-9]{4}\\.[a-f0-9]{4}$"
        description:
          If the PHY reports an incorrect ID (or none at all) then the
          compatible list may contain an entry with the correct PHY ID
          in the above form.
          The first group of digits is the 16 bit Phy Identifier 1
          register, this is the chip vendor OUI bits 3:18. The
          second group of digits is the Phy Identifier 2 register,
          this is the chip vendor OUI bits 19:24, followed by 10
          bits of a vendor specific ID.

It would be fine to do this in the example in the binding, but i would
add a comment something like:

"Compatible generally only needed to make DT lint tools work. Mostly
not needed for real DT descriptions"

Examples often get cut/paste without thinking, and we don't really
want the compatible used unless it is really needed.

This is however a bigger problem than just PHYs. It applies to any
device which can be enumerated on a bus, e.g. USB, PCI. So maybe this
limitation of the DT linting tools should be fixed once at a higher
level?

>  (3) The main problem with the broken interrupt handling of the PHY
>      is that it will disturb other devices on that interrupt line.
>      IOW if the interrupt line is shared the PHY should fall back
>      to polling mode. I haven't found anything in the interrupt
>      subsys to query if a line is shared and I guess it's also
>      conceptually impossible to do such a thing, because there
>      might be any driver probed at a later time which also uses
>      that line.
>      Rob had the idea to walk the device tree and determine if
>      a particular interrupt is used by other devices, too. If
>      feasable, this sounds like a good enough heuristic for our
>      problem. Although there might be some edge cases, like
>      DT overlays loaded at linux runtime (?!).

My humble opinion is that it is not worth the complexity for just one
PHY which should work in polling mode without problems. I think the
boolean property you propose is KISS and does what is needed.

	Andrew
  

>> +
>> +      Affected PHYs (as far as known) are GPY215B and GPY215C.
>> +    type: boolean
>> +
>> +dependencies:
>> +  maxlinear,use-broken-interrupts: [ interrupts ]

Btw. I'd presume that the tools will also allow interrupts-extended, but 
that
doesn't seem to be the case. Do I need some kind of anyOf here?

>> +
>> +unevaluatedProperties: false
>> +
>> +examples:
>> +  - |
>> +    ethernet {
>> +        #address-cells = <1>;
>> +        #size-cells = <0>;
>> +
>> +        ethernet-phy@0 {
>> +            reg = <0>;
>> +            interrupts-extended = <&intc 0>;
>> +            maxlinear,use-broken-interrupts;
> 
> This is never actually checked by be schema because there is nothing to
> match on. If you want custom properties, then you need a compatible.

I can add an unwanted compatible here, or skip the example altogether. 
But
what puzzles me is that this schema pulls in the ethernet-phy.yaml. The 
latter
then has a custom select statement on the $nodename and even a comment:

# The dt-schema tools will generate a select statement first by using
# the compatible, and second by using the node name if any. In our
# case, the node name is the one we want to match on, while the
# compatible is optional.

Why doesn't that work?

-michael