[EXT] Re: [PATCH v2 1/7] ASoC: dt-bindings: fsl_rpmsg: Add a property to assign the rpmsg channel

[Chancel Liu]

> >>> Add a string property to assign the rpmsg channel this sound card sits
> >>> on. It also represents the name of ASoC platform driver. This property
> >>> can be omitted if there is only one sound card and it sits on
> >>> "rpmsg-audio-channel".
> >>>
> >>> Signed-off-by: Chancel Liu <chancel.liu at nxp.com>
> >>> ---
> >>>  .../devicetree/bindings/sound/fsl,rpmsg.yaml  | 37
> ++++++++++++++++++-
> >>>  1 file changed, 35 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/sound/fsl,rpmsg.yaml
> >> b/Documentation/devicetree/bindings/sound/fsl,rpmsg.yaml
> >>> index d370c98a62c7..3744ae794c00 100644
> >>> --- a/Documentation/devicetree/bindings/sound/fsl,rpmsg.yaml
> >>> +++ b/Documentation/devicetree/bindings/sound/fsl,rpmsg.yaml
> >>> @@ -11,8 +11,11 @@ maintainers:
> >>>
> >>>  description: |
> >>>    fsl_rpmsg is a virtual audio device. Mapping to real hardware devices
> >>> -  are SAI, DMA controlled by Cortex M core. What we see from Linux
> >>> -  side is a device which provides audio service by rpmsg channel.
> >>> +  are SAI, MICFIL, DMA controlled by Cortex M core. What we see from
> >>> +  Linux side is a device which provides audio service by rpmsg channel.
> >>> +  We can create different sound cards which access different hardwares
> >>> +  such as SAI, MICFIL, .etc through building rpmsg channels between
> >>> +  Cortex-A and Cortex-M.
> >>>
> >>>  properties:
> >>>    compatible:
> >>> @@ -85,6 +88,17 @@ properties:
> >>>        This is a boolean property. If present, the receiving function
> >>>        will be enabled.
> >>>
> >>> +  fsl,rpmsg-channel-name:
> >>> +    $ref: /schemas/types.yaml#/definitions/string
> >>> +    description: |
> >>> +      A string property to assign rpmsg channel this sound card sits on.
> >>> +      It also represents the name of ASoC platform driver. This property
> >>
> >> That's a Linux detail which doesn't belong in DT.
> >>
> >
> > We pass hardware parameters in dts node to set up clocks or other
> > configurations. These configurations are finally sent to Cortex-M by
> > rpmsg channel because Cortex-M actually controls real hardware devices.
> > If there's only one sound card sits on one rpmsg channel we will not
> > need this property. But if there are several sound cards we need to
> > specify correct rpmsg channel. Thus hardware configurations can be
> > properly sent to Cortex-M. From this level to speak, this property is
> > hardware-related since rpmsg channel represents the real hardware audio
> > controller.
> >
> > Here I attach the discussion in version 1 patches for your information:
> > ---
> > This property aims to tell the ASoC driver which rpmsg channel the
> > sound card depends on. If there are several sound cards sit on rpmsg,
> > we should pass correct information in dts node to specify the name of
> > rpmsg channel. That is why I meant to add this property.
> >
> > Actually this property is hardware-related. As we discussed before,
> > this kind of sound card based on rpmsg works under this mechanism
> > Cortex-A core tells the Cortex-M core configuration of the PCM
> > parameters then Cortex-M controls real hardware devices. This property
> > specifying rpmsg channel represents the real hardware audio controller.
> > ---
> >
> > That's my idea adding this property. Do you have any suggstion?
> 
> I think you misunderstood the comment. Rob's comment was directly below
> a line which he referred to. That line contained a statement referring
> to Linux drivers. Anything related to Linux drivers does not belong to DT.
> 
> 
> Best regards,
> Krzysztof

Thanks for explaining the meaning and giving more details. I will
delete the statement referring to linux drivers. Indeed this property
is designed to assign the rpmsg channel name.
Does it look better if I modify the code like this:

+  fsl,rpmsg-channel-name:
+    $ref: /schemas/types.yaml#/definitions/string
+    description: |
+      A string property to assign rpmsg channel this sound card sits on.
+      This property can be omitted if there is only one sound card and it sits
+      on "rpmsg-audio-channel".
+    enum:
+      - rpmsg-audio-channel
+      - rpmsg-micfil-channel

Regards, 
Chancel Liu