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

[Wesley Cheng]

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@xxxxxxxxxxx>
> > ---
> >   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