On Mon, Feb 19, 2024 at 12:27:18PM +0200, Mathias Nyman wrote: > On 17.2.2024 17.25, Greg KH wrote: > > On Fri, Feb 16, 2024 at 04:09:26PM -0800, 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: > > > 1. Adding ASoC binding layer > > > 2. Create a USB backend for Q6DSP > > > 3. Introduce XHCI interrupter support > > > 4. 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 > > > > I've applied patches 1-10 and the 2 dts changes here, as those all had > > acks from the relevant maintainers already. > > > > Patch 10/10 is based on an old POC patch by me, but it's heavily modified. > > It looks like it does a few minor things that are not optimal, like extra > spinlock/unlock, and wait_for_completion_timeout() with magical timeout value. > I haven't tested this version, but I guess any fixes or cleanups can be done > later on top of it. I can revert it now if you want, just let me know. thanks, greg k-h
