Re: [PATCH v3 01/25] dt-bindings: soc: qcom: Add bindings for APR bus

Srinivas Kandagatla
2018-02-20T09:33:40Z

Thanks for your review comments,

On 18/02/18 23:04, Rob Herring wrote:
> On Wed, Feb 14, 2018 at 09:13:23AM +0000, Srinivas Kandagatla wrote:
>> Thanks for the review,
>>
>> On 13/02/18 23:12, Rob Herring wrote:
>>> On Tue, Feb 13, 2018 at 04:58:13PM +0000, srinivas.kandagatla@linaro.org wrote:
>>>> From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>>>>
>>>> This patch add dt bindings for Qualcomm APR (Asynchronous Packet Router)
>>>> bus driver. This bus is used for communicating with DSP which provides
>>>> audio and various other services to cpu.
>>>>
>>>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>>>> ---
>>>> .../devicetree/bindings/soc/qcom/qcom,apr.txt | 83 ++++++++++++++++++++++
>>>> 1 file changed, 83 insertions(+)
>>>> create mode 100644 Documentation/devicetree/bindings/soc/qcom/qcom,apr.txt
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/soc/qcom/qcom,apr.txt b/Documentation/devicetree/bindings/soc/qcom/qcom,apr.txt
>>>> new file mode 100644
>>>> index 000000000000..1b95fbfed348
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/soc/qcom/qcom,apr.txt
>>>> @@ -0,0 +1,83 @@
>>>> +Qualcomm APR (Asynchronous Packet Router) binding
>>>> +
>>>> +This binding describes the Qualcomm APR. APR is a IPC protocol for
>>>> +communication between Application processor and QDSP. APR is mainly
>>>> +used for audio/voice services on the QDSP.
>>>> +
>>>> +- compatible:
>>>> + Usage: required
>>>> + Value type: <stringlist>
>>>> + Definition: must be "qcom,apr-v<VERSION-NUMBER>", example "qcom,apr-v2"
>>>> +
>>>> +- qcom,apr-dest-domain-id
>>>> + Usage: required
>>>> + Value type: <prop-encoded-array>
>>>> + Definition: Destination processor ID.
>>>> + Possible values are :
>>>> + 1 - APR simulator
>>>> + 2 - PC
>>>> + 3 - MODEM
>>>> + 4 - ADSP
>>>> + 5 - APPS
>>>> + 6 - MODEM2
>>>> + 7 - APPS2
>>>> +
>>>> += APR SERVICES
>>>> +Each subnode of the APR node can represent service tied to this apr. The name
>>>> +of the nodes are not important. The properties of these nodes are defined
>>>> +by the individual bindings for the specific service
>>>> +- but must contain the following property:
>>>> +
>> ...
>>>> += APR DEVICES:
>>>> +Each subnode of the APR node can represent devices tied to this apr, like
>>>> +sound-card. The properties of these nodes are defined by the individual
>>>> +bindings for the specific device.
>>>
>>> It's not a good design generally to mix different types of nodes at one
>>> level.
>>
>> I agree, may be I can split the services and devices into different subnodes
>> like below, which should avoid mixing different types of nodes.
>>
>> Does this sound good to you?
>
> Seems your original example wasn't so complete...
>
Yep, I will fix it in next version.
> I don't see why you need all these nodes in the first place. For a
> single SoC, how much does all this vary?
>
It might not vary for a given SoC, but It does vary across the SoCs.
Also the versions of each service are independent to each other.
>>
>> apr {
>> compatible = "qcom,apr-v2";
>> qcom,smd-channels = "apr_audio_svc";
>> qcom,apr-dest-domain-id = <APR_DOMAIN_ADSP>;
>>
>> apr-services {
>> q6core {
>> qcom,apr-svc-name = "CORE";
>> qcom,apr-svc-id = <APR_SVC_ADSP_CORE>;
>> compatible = "qcom,q6core";
>> };
>>
>> q6afe: q6afe {
>> compatible = "qcom,q6afe";
>> qcom,apr-svc-name = "AFE";
>> qcom,apr-svc-id = <APR_SVC_AFE>;
>> #sound-dai-cells = <1>;
>> };
>>
>> q6asm: q6asm {
>> compatible = "qcom,q6asm";
>> qcom,apr-svc-name = "ASM";
>> qcom,apr-svc-id = <APR_SVC_ASM>;
>> #sound-dai-cells = <1>;
>> };
>>
>> q6adm: q6adm {
>> compatible = "qcom,q6adm";
>> qcom,apr-svc-name = "ADM";
>> qcom,apr-svc-id = <APR_SVC_ADM>;
>> #sound-dai-cells = <0>;
>> };
>
> All these DAI nodes could be a single node and the cell value be the
> svc-id?
No, DAI's here are both backends and frontends, and some of the services
like core, USM are not DAI's

Are you also saying that we should have a single driver entity for all
these services?

>
>> };
>>
>> apr-devices {
>> audio {
>> compatible = "qcom,msm8996-snd-card";
>
> This is a pseudo device. Why not put it at the top level like other
> sound cards?

APR bus depends on the state of DSP services, which can go off if the
DSP crashes or DSP is stopped. If we remove this sound card out of apr
bus then the sound card dependency on apr bus is totally lost.

Main purpose of having sound card under this bus is that the sound card
should register/unregister depending up the apr channel presence/absence
respectively.

thanks,
srini
>
>> ...
>> };
>> };
>> };
>>
>>
>>
>>
>>>
>>>> +
>>>> += EXAMPLE
>>>> +The following example represents a QDSP based sound card on a MSM8996 device
>>>> +which uses apr as communication between Apps and QDSP.
>>>> +
>>>> + apr {
>>>> + compatible = "qcom,apr-v2";
>>>> + qcom,smd-channels = "apr_audio_svc";
>>>> + qcom,apr-dest-domain-id = <APR_DOMAIN_ADSP>;
>>>> +
>>>> + q6core {
>>>> + compatible = "qcom,q6core";
>>>> + qcom,apr-svc-name = "CORE";
>>>> + qcom,apr-svc-id = <APR_SVC_ADSP_CORE>;
>>>> + };
>>>> +
>>>> + q6afe {
>>>> + compatible = "qcom,q6afe";
>>>> + qcom,apr-svc-name = "AFE";
>>>> + qcom,apr-svc-id = <APR_SVC_AFE>;
>>>> + };
>>>> +
>>>> + audio {
>>>> + compatible = "qcom,msm8996-snd-card";
>>>> + ...
>>>> + };
>>>> + };
>>>> --
>>>> 2.15.1
>>>>