linux-kernel - Re: [alsa-devel] [RESEND PATCH v4 1/4] dt-bindings: soundwire: add slave bindings

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Message-ID: <37be6b6d-7e7f-2cd6-f9e9-f0cac48791ad@linaro.org>
Date:   Fri, 23 Aug 2019 16:57:25 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        broonie@...nel.org, robh+dt@...nel.org, vkoul@...nel.org
Cc:     devicetree@...r.kernel.org, alsa-devel@...a-project.org,
        bgoswami@...eaurora.org, spapothi@...eaurora.org,
        lgirdwood@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [alsa-devel] [RESEND PATCH v4 1/4] dt-bindings: soundwire: add
 slave bindings



On 23/08/2019 16:41, Pierre-Louis Bossart wrote:
> 
> 
> On 8/22/19 6:37 PM, Srinivas Kandagatla wrote:
>> This patch adds bindings for Soundwire Slave devices that includes how
>> SoundWire enumeration address and Link ID are used to represented in
>> SoundWire slave device tree nodes.
>>
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>> ---
>>   .../soundwire/soundwire-controller.yaml       | 75 +++++++++++++++++++
>>   1 file changed, 75 insertions(+)
>>   create mode 100644 
>> Documentation/devicetree/bindings/soundwire/soundwire-controller.yaml
>>
>> diff --git 
>> a/Documentation/devicetree/bindings/soundwire/soundwire-controller.yaml b/Documentation/devicetree/bindings/soundwire/soundwire-controller.yaml 
>>
>> new file mode 100644
>> index 000000000000..91aa6c6d6266
>> --- /dev/null
>> +++ 
>> b/Documentation/devicetree/bindings/soundwire/soundwire-controller.yaml
>> @@ -0,0 +1,75 @@
>> +# SPDX-License-Identifier: GPL-2.0
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/soundwire/soundwire-controller.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: SoundWire Controller Generic Binding
>> +
>> +maintainers:
>> +  - Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>> +
>> +description: |
>> +  SoundWire busses can be described with a node for the SoundWire 
>> controller
>> +  device and a set of child nodes for each SoundWire slave on the bus.
>> +
>> +properties:
>> +  $nodename:
>> +    pattern: "^soundwire(@.*|-[0-9a-f])*$"
>> +
>> +  "#address-cells":
>> +    const: 2
>> +
>> +  "#size-cells":
>> +    const: 0
>> +
>> +patternProperties:
>> +  "^.*@[0-9a-f]+$":
>> +    type: object
>> +
>> +    properties:
>> +      compatible:
>> +      pattern: "^sdw[0-9][0-9a-f]{4}[0-9a-f]{4}[0-9a-f]{2}$"
> 
> So is this a 64-bit value, as in the MIPI spec, or is this part of the 
> _ADR description?

Rob did not like encoding compatible string exactly like _ADR encoding.

https://lkml.org/lkml/2019/8/22/490

> I also don't get why the first item in in base10?
> 

As this corresponds to Soundwire Version, and I have no visibility of 
version number encoding after reaching number 9 in this field.

This can be updated once we have more info on how the Version encoding 
will look like in future.

Idea of limiting regex to [0-9] for version is to enforce some checking!

--srini

> 
>> +      description:
>> +      Is the textual representation of SoundWire Enumeration
>> +      address. compatible string should contain SoundWire Version ID,
>> +      Manufacturer ID, Part ID and Class ID in order and shall be in
>> +      lower-case hexadecimal with leading zeroes.
>> +      Valid sizes of these fields are
>> +      Version ID is 1 nibble, number '0x1' represents SoundWire 1.0
>> +      and '0x2' represents SoundWire 1.1 and so on.
>> +      MFD is 4 nibbles
>> +      PID is 4 nibbles
>> +      CID is 2 nibbles
>> +      More Information on detail of encoding of these fields can be
>> +      found in MIPI Alliance DisCo & SoundWire 1.0 Specifications.
>> +
>> +      reg:
>> +        maxItems: 1
>> +        description:
>> +          Instance ID and Link ID of SoundWire Device Address.
>> +
>> +    required:
>> +      - compatible
>> +      - reg
>> +
>> +examples:
>> +  - |
>> +    soundwire@...0000 {
>> +        #address-cells = <2>;
>> +        #size-cells = <0>;
>> +        compatible = "qcom,soundwire-v1.5.0";
>> +        reg = <0x0c2d0000 0x2000>;
>> +
>> +        speaker@1 {
>> +            compatible = "sdw10217201000";
>> +            reg = <1 0>;
>> +        };
>> +
>> +        speaker@2 {
>> +            compatible = "sdw10217201000";
>> +            reg = <2 0>;
>> +        };
>> +    };
>> +
>> +...
>>