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

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@quicinc.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.

thanks,

Takashi