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

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Date:	Fri, 6 Mar 2015 10:07:01 -0600
From:	Kumar Gala <galak@...eaurora.org>
To:	Kenneth Westfield <kwestfie@...eaurora.org>
Cc:	Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.de>,
	Liam Girdwood <lgirdwood@...il.com>,
	Banajit Goswami <bgoswami@...eaurora.org>,
	Patrick Lai <plai@...eaurora.org>,
	David Brown <davidb@...eaurora.org>,
	Bryan Huntsman <bryanh@...eaurora.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	ALSA Mailing List <alsa-devel@...a-project.org>,
	MSM Mailing List <linux-arm-msm@...r.kernel.org>,
	Device Tree Mailing List <devicetree@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Patch V7 02/10] ASoC: qcom: Document LPASS CPU bindings


On Mar 5, 2015, at 7:51 PM, Kenneth Westfield <kwestfie@...eaurora.org> 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@...eaurora.org> 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.
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

- k
-- 
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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