Re: [Patch V7 02/10] ASoC: qcom: Document LPASS CPU bindings

From: Kenneth Westfield
Date: Fri Mar 06 2015 - 17:04:01 EST


On Fri, Mar 06, 2015 at 10:07:01AM -0600, Kumar Gala wrote:
> On Mar 5, 2015, at 7:51 PM, Kenneth Westfield <kwestfie@xxxxxxxxxxxxxx> wrote:
> > On Thu, Mar 05, 2015 at 12:52:30PM -0600, Kumar Gala wrote:
> >> On Mar 3, 2015, at 6:21 PM, Kenneth Westfield <kwestfie@xxxxxxxxxxxxxx> wrote:
> >>
> >>> +++ b/Documentation/devicetree/bindings/sound/qcom,lpass-cpu.txt
> >>> @@ -0,0 +1,49 @@
> >>> +* Qualcomm Technologies LPASS CPU DAI
> >>> +
> >>> +Required subnodes:
> >>> +
> >>> +- qcom,adsp : Audio DSP sub-node
> >>> +
> >>> +Optional Audio DSP subnode properties:
> >>> +
> >>> +- status : "disabled" indicates the adsp is not available.
> >>> +
> >>
> >> What is the intent of this subnode?
> >>
> >
> > From the cover letter:
> > Even though the ipq806x LPASS does not contain an audio DSP, other SOCs
> > do have one. For those SOCs, the audio DSP typically controls the
> > hardware blocks in the LPASS. Hence, different CPU DAI driver(s) would
> > need to be used in order to facilitate audio with the DSP. As such, the
> > LPASS DT contains an adsp subnode, which is disabled for this SOC. The
> > same subnode should be enabled and populated for other SOCs that do
> > contain an audio DSP. Not using the audio DSP would require different
> > CPU DAI driver(s), in addition to possible bootloader and/or firmware
> > changes.
> >
> > This was the result of a request from Mark. See here:
> > http://thread.gmane.org/gmane.linux.drivers.devicetree/109331/focus=11633
>
> Two quick comments before I read Mark?s comments.
>
> 1. Its not normal practice to put something into a DT that does not exist. Having a node, but marking it disabled implies existence.

Will change the DT definition to optional.

> 2. How would one normally address the audio DSP if it did exist. I?m just wondering if having a subnode is the proper solution vs maybe a phandle

The audio DSP is, in fact, contained within the audio subsystem. The
representation of that relationship in the DT, I believe, would be a subnode.
OTOH, if there is a strong sentiment towards using a phandle, that would be
fine with me.

--
Kenneth Westfield
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
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