Apologies for the long delay in addressing some of your comments and feedback. I understand it is difficult to refresh a lot of the material after such a long gap, but hopefully I have addressed some of the concerns in the latest revision. Appreciate all the suggestions/reviews!
Thanks Wesley Cheng
On 7/24/2023 7:33 PM, Wesley Cheng wrote:
Several Qualcomm based chipsets can support USB audio offloading to a dedicated audio DSP, which can take over issuing transfers to the USB host controller. The intention is to reduce the load on the main processors in the SoC, and allow them to be placed into lower power modes. There are several parts to this design:
Adding ASoC binding layer
Create a USB backend for Q6DSP
Introduce XHCI interrupter support
Create vendor ops for the USB SND driver
USB | ASoC
| _________________________ | |sm8250 platform card | | |_________________________| | | | | ___V____ ____V____ | |Q6USB | |Q6AFE | | |"codec" | |"cpu" | | |________| |_________| | ^ ^ ^ | | |________| | ___V____ | | |SOC-USB | | ________ ________ | | ||USB SND |<--->|QC offld|<------------>|________| | |(card.c)| | |<---------- | |________| |________|___ | | | ^ ^ | | | ____________V_________ | | | | | |APR/GLINK | __ V_______________V_____ | | | |______________________| |USB SND (endpoint.c) | | | | ^ |_________________________| | | | | ^ | | | ___________V___________ | | | |->|audio DSP | ___________V_____________ | | |_______________________| |XHCI HCD |<- | |_________________________| |
Adding ASoC binding layer: soc-usb: Intention is to treat a USB port similar to a headphone jack. The port is always present on the device, but cable/pin status can be enabled/disabled. Expose mechanisms for USB backend ASoC drivers to communicate with USB SND.
Create a USB backend for Q6DSP: q6usb: Basic backend driver that will be responsible for maintaining the resources needed to initiate a playback stream using the Q6DSP. Will be the entity that checks to make sure the connected USB audio device supports the requested PCM format. If it does not, the PCM open call will fail, and userpsace ALSA can take action accordingly.
Introduce XHCI interrupter support: XHCI HCD supports multiple interrupters, which allows for events to be routed to different event rings. This is determined by "Interrupter Target" field specified in Section "6.4.1.1 Normal TRB" of the XHCI specification.
Events in the offloading case will be routed to an event ring that is assigned to the audio DSP.
Create vendor ops for the USB SND driver: qc_audio_offload: This particular driver has several components associated with it:
- QMI stream request handler
- XHCI interrupter and resource management
- audio DSP memory management
When the audio DSP wants to enable a playback stream, the request is first received by the ASoC platform sound card. Depending on the selected route, ASoC will bring up the individual DAIs in the path. The Q6USB backend DAI will send an AFE port start command (with enabling the USB playback path), and the audio DSP will handle the request accordingly.
Part of the AFE USB port start handling will have an exchange of control messages using the QMI protocol. The qc_audio_offload driver will populate the buffer information:
- Event ring base address
- EP transfer ring base address
and pass it along to the audio DSP. All endpoint management will now be handed over to the DSP, and the main processor is not involved in transfers.
Overall, implementing this feature will still expose separate sound card and PCM devices for both the platorm card and USB audio device: 0 [SM8250MTPWCD938]: sm8250 - SM8250-MTP-WCD9380-WSA8810-VA-D SM8250-MTP-WCD9380-WSA8810-VA-DMIC 1 [Audio ]: USB-Audio - USB Audio Generic USB Audio at usb-xhci-hcd.1.auto-1.4, high speed
This is to ensure that userspace ALSA entities can decide which route to take when executing the audio playback. In the above, if card#1 is selected, then USB audio data will take the legacy path over the USB PCM drivers, etc...
This feature was validated using:
- tinymix: set/enable the multimedia path to route to USB backend
- tinyplay: issue playback on platform card
Changelog
Changes in v4:
- Rebased to xhci/for-usb-next
- Addressed some dt-bindings comments
XHCI:
- Pulled in latest changes from Mathias' feature_interrupters branch:
https://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git/log/?h=featu...
- Fixed commit text and signage for the XHCI sideband/interrupter related changes
- Added some logic to address the FIXME tags mentioned throughout the commits, such
as handling multi segment rings and building the SGT, locking concerns, and ep cleanup operations.
- Removed some fixme tags for conditions that may not be needed/addressed.
- Repurposed the new endpoint stop sync API to be utilized in other places.
- Fixed potential compile issue if XHCI sideband config is not defined.
ASoC:
- Added sound jack control into the Q6USB driver. Allows for userpsace to know when
an offload capable device is connected.
USB SND:
- Avoided exporting _snd_pcm_hw_param_set based on Takashi's recommendation.
- Split USB QMI packet header definitions into a separate commit. This is used to
properly allow the QMI interface driver to parse and route QMI packets accordingly
- Added a "depends on" entry when enabling QC audio offload to avoid compile time
issues.
Changes in v3:
- Changed prefix from RFC to PATCH
- Rebased entire series to usb-next
- Updated copyright years
XHCI:
- Rebased changes on top of XHCI changes merged into usb-next, and only added
changes that were still under discussion.
- Added change to read in the "num-hc-interrupters" device property.
ASoC:
qusb6 USB backend
Incorporated suggestions to fetch iommu information with existing APIs
Added two new sound kcontrols to fetch offload status and offload device selection.
offload status - will return the card and pcm device in use tinymix -D 0 get 1 --> 1, 0 (offload in progress on card#1 pcm#0)
device selection - set the card and pcm device to enable offload on. Ex.: tinymix -D 0 set 1 2 0 --> sets offload on card#2 pcm#0 (this should be the USB card)
USB SND:
- Fixed up some locking related concerns for registering platform ops.
- Moved callbacks under the register_mutex, so that
- Modified APIs to properly pass more information about the USB SND device, so
that the Q6USB backend can build a device list/map, in order to monitor offload status and device selection.
Changes in v2:
XHCI:
- Replaced XHCI and HCD changes with Mathias' XHCI interrupter changes
in his tree: https://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git/log/?h=featu...
Adjustments made to Mathias' changes:
Created xhci-intr.h to export/expose interrupter APIs versus exposing xhci.h. Moved dependent structures to this file as well. (so clients can parse out information from "struct xhci_interrupter")
Added some basic locking when requesting interrupters.
Fixed up some sanity checks.
Removed clearing of the ERSTBA during freeing of the interrupter. (pending issue where SMMU fault occurs if DMA addr returned is 64b - TODO)
Clean up pending events in the XHCI secondary interrupter. While testing USB
bus suspend, it was seen that on bus resume, the xHCI HC would run into a command timeout.
- Added offloading APIs to xHCI to fetch transfer and event ring information.
ASoC:
- Modified soc-usb to allow for multiple USB port additions. For this to work,
the USB offload driver has to have a reference to the USB backend by adding a "usb-soc-be" DT entry to the device saved into XHCI sysdev.
- Created separate dt-bindings for defining USB_RX port.
- Increased APR timeout to accommodate the situation where the AFE port start
command could be delayed due to having to issue a USB bus resume while handling the QMI stream start command.
USB SND:
- Added a platform ops during usb_audio_suspend(). This allows for the USB
offload driver to halt the audio stream when system enters PM suspend. This ensures the audio DSP is not issuing transfers on the USB bus.
- Do not override platform ops if they are already populated.
- Introduce a shared status variable between the USB offload and USB SND layers,
to ensure that only one path is active at a time. If the USB bus is occupied, then userspace is notified that the path is busy.
Mathias Nyman (3): xhci: add support to allocate several interrupters xhci: add helper to stop endpoint and wait for completion xhci: sideband: add initial api to register a sideband entity
Wesley Cheng (29): usb: host: xhci-mem: Cleanup pending secondary event ring events usb: host: xhci-mem: Allow for interrupter clients to choose specific index ASoC: Add SOC USB APIs for adding an USB backend ASoC: dt-bindings: qcom,q6dsp-lpass-ports: Add USB_RX port ASoC: qcom: qdsp6: Introduce USB AFE port to q6dsp ASoC: qdsp6: q6afe: Increase APR timeout ASoC: qcom: Add USB backend ASoC driver for Q6 sound: usb: card: Introduce USB SND platform op callbacks sound: usb: Export USB SND APIs for modules dt-bindings: usb: dwc3: Add snps,num-hc-interrupters definition usb: dwc3: Add DT parameter to specify maximum number of interrupters usb: host: xhci-plat: Set XHCI max interrupters if property is present sound: usb: pcm: Export fixed rate check USB SND API sound: usb: qcom: Add USB QMI definitions sound: usb: Introduce QC USB SND offloading support sound: usb: card: Check for support for requested audio format sound: soc: soc-usb: Add PCM format check API for USB backend sound: soc: qcom: qusb6: Ensure PCM format is supported by USB audio device sound: usb: Prevent starting of audio stream if in use ASoC: dt-bindings: Add Q6USB backend bindings ASoC: dt-bindings: Update example for enabling USB offload on SM8250 ASoC: qcom: qdsp6: q6afe: Split USB AFE dev_token param into separate API sound: Pass USB SND card and PCM information to SOC USB sound: soc: qdsp6: Add SND kcontrol to select offload device sound: soc: qdsp6: Add SND kcontrol for fetching offload status sound: soc: qcom: q6usb: Add headphone jack for offload connection status sound: usb: qc_audio_offload: Use card and PCM index from QMI request sound: usb: card: Allow for rediscovery of connected USB SND devices sound: soc: soc-usb: Rediscover USB SND devices on USB port add
.../bindings/sound/qcom,q6usb-dais.yaml | 49 + .../bindings/sound/qcom,sm8250.yaml | 15 + .../devicetree/bindings/usb/snps,dwc3.yaml | 13 + arch/arm64/boot/dts/qcom/sm8350.dtsi.rej | 14 + arch/arm64/configs/defconfig.rej | 24 + drivers/usb/dwc3/core.c | 12 + drivers/usb/dwc3/core.h | 2 + drivers/usb/dwc3/host.c | 5 +- drivers/usb/host/Kconfig | 9 + drivers/usb/host/Makefile | 4 + drivers/usb/host/xhci-debugfs.c | 2 +- drivers/usb/host/xhci-hub.c | 29 +- drivers/usb/host/xhci-mem.c | 167 +- drivers/usb/host/xhci-plat.c | 2 + drivers/usb/host/xhci-ring.c | 2 +- drivers/usb/host/xhci-sideband.c | 195 ++ drivers/usb/host/xhci.c | 109 +- drivers/usb/host/xhci.h | 102 +- .../sound/qcom,q6dsp-lpass-ports.h | 1 + include/linux/usb/xhci-intr.h | 86 + include/linux/usb/xhci-sideband.h | 90 + include/sound/q6usboffload.h | 20 + include/sound/soc-usb.h | 39 + sound/core/oss/pcm_oss.c | 4 +- sound/soc/Makefile | 2 +- sound/soc/qcom/Kconfig | 4 + sound/soc/qcom/qdsp6/Makefile | 1 + sound/soc/qcom/qdsp6/q6afe-dai.c | 50 + sound/soc/qcom/qdsp6/q6afe.c | 208 +- sound/soc/qcom/qdsp6/q6afe.h | 47 +- sound/soc/qcom/qdsp6/q6dsp-lpass-ports.c | 23 + sound/soc/qcom/qdsp6/q6dsp-lpass-ports.h | 1 + sound/soc/qcom/qdsp6/q6routing.c | 9 + sound/soc/qcom/qdsp6/q6usb.c | 458 +++++ sound/soc/soc-usb.c | 197 ++ sound/usb/Kconfig | 15 + sound/usb/Makefile | 2 +- sound/usb/card.c | 85 + sound/usb/card.h | 32 + sound/usb/endpoint.c | 2 + sound/usb/helper.c | 1 + sound/usb/pcm.c | 29 +- sound/usb/pcm.h | 12 + sound/usb/qcom/Makefile | 2 + sound/usb/qcom/qc_audio_offload.c | 1820 +++++++++++++++++ sound/usb/qcom/usb_audio_qmi_v01.c | 892 ++++++++ sound/usb/qcom/usb_audio_qmi_v01.h | 162 ++ 47 files changed, 4870 insertions(+), 179 deletions(-) create mode 100644 Documentation/devicetree/bindings/sound/qcom,q6usb-dais.yaml create mode 100644 arch/arm64/boot/dts/qcom/sm8350.dtsi.rej create mode 100644 arch/arm64/configs/defconfig.rej create mode 100644 drivers/usb/host/xhci-sideband.c create mode 100644 include/linux/usb/xhci-intr.h create mode 100644 include/linux/usb/xhci-sideband.h create mode 100644 include/sound/q6usboffload.h create mode 100644 include/sound/soc-usb.h create mode 100644 sound/soc/qcom/qdsp6/q6usb.c create mode 100644 sound/soc/soc-usb.c create mode 100644 sound/usb/qcom/Makefile create mode 100644 sound/usb/qcom/qc_audio_offload.c create mode 100644 sound/usb/qcom/usb_audio_qmi_v01.c create mode 100644 sound/usb/qcom/usb_audio_qmi_v01.h