linux-kernel - Re: [PATCH v5 18/32] sound: usb: Introduce QC USB SND offloading support

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Date:   Mon, 11 Sep 2023 10:59:20 -0700
From:   Wesley Cheng <quic_wcheng@...cinc.com>
To:     Takashi Iwai <tiwai@...e.de>
CC:     <srinivas.kandagatla@...aro.org>, <mathias.nyman@...el.com>,
        <perex@...ex.cz>, <lgirdwood@...il.com>, <andersson@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <gregkh@...uxfoundation.org>,
        <Thinh.Nguyen@...opsys.com>, <broonie@...nel.org>,
        <bgoswami@...cinc.com>, <tiwai@...e.com>, <robh+dt@...nel.org>,
        <agross@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <alsa-devel@...a-project.org>,
        <devicetree@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <quic_jackp@...cinc.com>, <quic_plai@...cinc.com>
Subject: Re: [PATCH v5 18/32] sound: usb: Introduce QC USB SND offloading
 support

Hi Takashi,

On 9/7/2023 8:51 AM, Takashi Iwai wrote:
> On Tue, 29 Aug 2023 23:06:43 +0200,
> Wesley Cheng wrote:
>>
>> Several Qualcomm SoCs have a dedicated audio DSP, which has the ability to
>> support USB sound devices.  This vendor driver will implement the required
>> handshaking with the DSP, in order to pass along required resources that
>> will be utilized by the DSP's USB SW.  The communication channel used for
>> this handshaking will be using the QMI protocol.  Required resources
>> include:
>> - Allocated secondary event ring address
>> - EP transfer ring address
>> - Interrupter number
>>
>> The above information will allow for the audio DSP to execute USB transfers
>> over the USB bus.  It will also be able to support devices that have an
>> implicit feedback and sync endpoint as well.  Offloading these data
>> transfers will allow the main/applications processor to enter lower CPU
>> power modes, and sustain a longer duration in those modes.
>>
>> Audio offloading is initiated with the following sequence:
>> 1. Userspace configures to route audio playback to USB backend and starts
>> playback on the platform soundcard.
>> 2. The Q6DSP AFE will communicate to the audio DSP to start the USB AFE
>> port.
>> 3. This results in a QMI packet with a STREAM enable command.
>> 4. The QC audio offload driver will fetch the required resources, and pass
>> this information as part of the QMI response to the STREAM enable command.
>> 5. Once the QMI response is received the audio DSP will start queuing data
>> on the USB bus.
>>
>> Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>
>> ---
>>   sound/usb/Kconfig                 |   15 +
>>   sound/usb/Makefile                |    2 +-
>>   sound/usb/qcom/Makefile           |    2 +
>>   sound/usb/qcom/qc_audio_offload.c | 1813 +++++++++++++++++++++++++++++
>>   4 files changed, 1831 insertions(+), 1 deletion(-)
>>   create mode 100644 sound/usb/qcom/Makefile
>>   create mode 100644 sound/usb/qcom/qc_audio_offload.c
>>
>> diff --git a/sound/usb/Kconfig b/sound/usb/Kconfig
>> index 4a9569a3a39a..da5838656baa 100644
>> --- a/sound/usb/Kconfig
>> +++ b/sound/usb/Kconfig
>> @@ -176,6 +176,21 @@ config SND_BCD2000
>>   	  To compile this driver as a module, choose M here: the module
>>   	  will be called snd-bcd2000.
>>   
>> +config QC_USB_AUDIO_OFFLOAD
> 
> Keep SND_ prefix for consistency.  And, at best, align with the module
> name.
> 
>> +	tristate "Qualcomm Audio Offload driver"
>> +	depends on QCOM_QMI_HELPERS && SND_USB_AUDIO && USB_XHCI_SIDEBAND
>> +	select SND_PCM
>> +	help
>> +	  Say Y here to enable the Qualcomm USB audio offloading feature.
>> +
>> +	  This module sets up the required QMI stream enable/disable
>> +	  responses to requests generated by the audio DSP.  It passes the
>> +	  USB transfer resource references, so that the audio DSP can issue
>> +	  USB transfers to the host controller.
>> +
>> +	  To compile this driver as a module, choose M here: the module
>> +	  will be called qc-audio-offload.
> 
> Hmm, you renamed it differently, no?  In the below:
> 
>> --- /dev/null
>> +++ b/sound/usb/qcom/Makefile
>> @@ -0,0 +1,2 @@
>> +snd-usb-audio-qmi-objs := usb_audio_qmi_v01.o qc_audio_offload.o
>> +obj-$(CONFIG_QC_USB_AUDIO_OFFLOAD) += snd-usb-audio-qmi.o
> 
> ... it's called snd-usb-audio-qmi.
> 

Will fix this, thanks.

Thanks
Wesley Cheng