Re: [RFC PATCH 2/3] dt-bindings: net: phy: Add support for AT803X

[Michael Walle <michael@walle.cc>]

Am 31. Oktober 2019 00:17:06 MEZ schrieb Andrew Lunn <andrew@lunn.ch>:
>On Wed, Oct 30, 2019 at 11:42:50PM +0100, Michael Walle wrote:
>> Document the Atheros AR803x PHY bindings.
>> 
>> Signed-off-by: Michael Walle <michael@walle.cc>
>> ---
>>  .../bindings/net/atheros,at803x.yaml          | 58
>+++++++++++++++++++
>>  include/dt-bindings/net/atheros-at803x.h      | 13 +++++
>>  2 files changed, 71 insertions(+)
>>  create mode 100644
>Documentation/devicetree/bindings/net/atheros,at803x.yaml
>>  create mode 100644 include/dt-bindings/net/atheros-at803x.h
>> 
>> diff --git
>a/Documentation/devicetree/bindings/net/atheros,at803x.yaml
>b/Documentation/devicetree/bindings/net/atheros,at803x.yaml
>> new file mode 100644
>> index 000000000000..60500fd90fd8
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/net/atheros,at803x.yaml
>> @@ -0,0 +1,58 @@
>> +# SPDX-License-Identifier: GPL-2.0+
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/net/atheros,at803x.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Atheros AR803x PHY
>> +
>> +maintainers:
>> +  - TBD
>
>Hi Michael
>
>If you don't want to maintain it, then list the PHY maintainers.
>
>> +
>> +description: |
>> +  Bindings for Atheros AR803x PHYs
>> +
>> +allOf:
>> +  - $ref: ethernet-phy.yaml#
>> +
>> +properties:
>> +  atheros,clk-out-frequency:
>> +    description: Clock output frequency in Hertz.
>> +    enum: [ 25000000, 50000000, 62500000, 125000000 ]
>> +
>> +  atheros,clk-out-strength:
>> +    description: Clock output driver strength.
>> +    enum: [ 0, 1, 2 ]
>> +
>> +  atheros,keep-pll-enabled:
>> +    description: |
>> +      If set, keep the PLL enabled even if there is no link. Useful
>if you
>> +      want to use the clock output without an ethernet link.
>> +    type: boolean
>> +
>> +  atheros,rgmii-io-1v8:
>> +    description: |
>> +      The PHY supports RGMII I/O voltages of 2.5V, 1.8V and 1.5V. By
>default,
>> +      the PHY uses a voltage of 1.5V. If this is set, the voltage
>will changed
>> +      to 1.8V.
>> +      The 2.5V voltage is only supported with an external supply
>voltage.
>
>So we can later add atheros,rgmii-io-2v5. That might need a regulator
>as well. Maybe add that 2.5V is currently not supported.

There is no special setting for the 2.5V mode. This is how it works: there is one voltage pad for the RGMII interface. Either you connect this pad to a 2.5V voltage or you leave it open (well you would connect some decoupling Cs). If you leave it open the internal LDO, which seems to be enabled in any case takes over, supplying 1.5V. then there is a bit in the debug register which can switch the internal LDO to 1.8V. So if you'll use 2.5V the bit is irrelevant. 

Like I said maybe a "rgmii-io-microvolts" is a better property and only in the 1800000 setting would turn on this bit. but then both other setting would be a noop. 

-michael