On Mar 6, 2015, at 4:03 PM, Kenneth Westfield kwestfie@codeaurora.org wrote:
On Fri, Mar 06, 2015 at 10:07:01AM -0600, Kumar Gala wrote:
On Mar 5, 2015, at 7:51 PM, Kenneth Westfield kwestfie@codeaurora.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@codeaurora.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.
- 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.
- 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.
Just depends on how we communicate with the DSP. If its mostly via MMIO access than a sub node makes sense. If its via some other RPC/communication mechanism than possibly a phandle. Trying to understand a bit more to than see what I’d recommend.
- k