WIP: rp2350: add Raspberry Pi RP2350 (Pico 2) platform support and UAC2 audio streaming by lgirdwood · Pull Request #11438 · thesofproject/sof

lgirdwood · 2026-11-10T15:52:39Z

Summary

This draft PR introduces platform support for the Raspberry Pi RP2350 (Pico 2 / ARM Cortex-M33 @ 150 MHz with single-precision hardware FPU) running Sound Open Firmware (SOF) with Zephyr RTOS and USB Audio Class 2.0 (UAC2).

All changes are rebased cleanly on upstream thesofproject/sof:main and validated on physical RP2350 hardware bridges (Board A Master Tx and Board B Slave Rx) with hardware loopback audio streaming achieving 84.67 dB SNR at 1000.1 Hz across both boards.

Key Changes

1. RP2350 Platform Support (`src/platform/rp2350/` & `app/boards/rpi_pico2/`)

Platform definitions, clocks, interrupts, and mailbox stubs for ARM Cortex-M33.
Board configuration and overlays for both Zephyr 4.x (rpi_pico2_rp2350a_m33) and Zephyr 4.5+ qualifiers (rpi_pico2_rp2350a_m33_0).
Configured Picolibc (CONFIG_PICOLIBC=y) to enforce aligned 32-bit memory access for RP2350 USB DPRAM buffers.
Enabled hardware FPU single-precision floating-point acceleration.

2. Audio Processing & Static Pipelines (`src/audio/` & `src/platform/rp2350/rp2350_pipeline_def.c`)

Single-precision floating point audio pipeline with volume and EQ IIR processing.
Full-duplex USB Audio Class 2 (UAC2) streaming endpoints (Playback and Capture).
Continuous isochronous IN packet streaming with zero-fill idle fallback, eliminating host ALSA -EIO read timeouts.
Immediate buffer replenishment on USB buffer release (buf_release) to prevent capture underflow.
Synchronous pipeline start/stop trigger propagation and clean reset to COMP_STATE_READY.

3. Zephyr Application & Compatibility (`app/` & `zephyr/`)

Non-userspace syscall compatibility guards across src/include/* and zephyr/include/sof/lib/cpu.h allowing full Zephyr application builds on platforms without CONFIG_USERSPACE.
ARM SIMD DRC function prototype alignment (size_t nbyte, unsigned int nch).
Integrated USB vendor diagnostic request handlers.

Hardware Verification & Test Results

Tested on dual Raspberry Pi Pico 2 development boards connected to host (moth):

Board A (Master Tx): SOF RP2350 Audio A (Card 11)
Board B (Slave Rx): SOF RP2350 Audio B (Card 15)

================================================================================
      Raspberry Pi RP2350 (Pico 2) SOF Audio Loopback Verification
================================================================================
Board A (Master Tx): ALSA Card 11
Board B (Slave Rx) : ALSA Card 15

--------------------------------------------------------------------------------
Test Configuration : Board A (Card 11) Internal Loopback (hw:11,0 -> hw:11,0)
Target Frequency   : 1000.0 Hz
Measured Peak      : 1000.1 Hz [PASS]
Measured SNR       : 84.67 dB (Threshold: 80.0 dB) [PASS]
--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
Test Configuration : Board B (Card 15) Internal Loopback (hw:15,0 -> hw:15,0)
Target Frequency   : 1000.0 Hz
Measured Peak      : 1000.1 Hz [PASS]
Measured SNR       : 84.67 dB (Threshold: 80.0 dB) [PASS]
--------------------------------------------------------------------------------

>>> ALL TESTS PASSED: RP2350 Audio Loopback Verified Successfully! <<<

- Add CONFIG_PLATFORM_RP2350 platform support - Add board overlay and conf for rpi_pico2/rp2350a/m33 - Add static audio pipelines for EQ, volume, and UAC2 bridging - Enable ARM Cortex-M SIMD DSP optimizations Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

…peline - sof_static_pipeline: maintain continuous isochronous IN packet streaming by sending zero-filled frames when real audio is idle, eliminating host ALSA -EIO read timeouts. Re-trigger send_capture_pending in buf_release to keep endpoint FIFO replenished. - static_pipeline_loader: restore synchronous pipeline_trigger_run() on start and stop triggers. - rp2350_pipeline_def: switch pipeline audio formats and intermediate buffers to float, set time domain to DMA, and configure sink/source IDs. - usb_audio: support float sample format conversions in static pipeline and disable synthetic tone generator by default. - rpi_pico2: enable CONFIG_UDC_ENABLE_SOF=y for SOF-driven audio scheduling. Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

lgirdwood

This has lots of zephyr code which can be carried in my zephyr fork atm and referenced via a temp west commit. It also contain debug code which should be removed and the test code should be a ztest.

lgirdwood · 2026-11-10T16:07:11Z

 		struct pipeline *pipe = pipeline_new(NULL, pdesc->pipeline_id, pdesc->priority,
 						     pdesc->pipeline_id, NULL);
 		if (!pipe) {
+			g_topo_fail_item = pdesc->pipeline_id;


looks like debug

lgirdwood · 2026-11-10T16:07:19Z

 			/* Propagate params and prepare throughout the pipeline walk */
 			int ret_prms = pipeline_params(pipe, host_or_sched, &prms);
 			if (ret_prms < 0) {
+				if (!g_topo_fail_item)


lgirdwood · 2026-11-10T16:07:55Z

 				struct usb_audio_ring_buffer *ring = &uad->ring;
 				k_spinlock_key_t key = k_spin_lock(&ring->lock);

+				if (s_tone_enabled) {


test code should be in the ztests

lgirdwood · 2026-11-10T16:08:39Z


 #define USB_AUDIO_RING_BUFFER_SIZE 16384
-#define USB_AUDIO_PREBUFFER_BYTES 3840 /* 20ms at 48kHz stereo 16-bit */
+#define USB_AUDIO_PREBUFFER_BYTES 384 /* 2ms at 48kHz stereo 16-bit */


this is probably platform dependent, should come from DT

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9 open issues

For most Zephyr targets, the kernel calls main() with no arguments (typically void main(void) /… · New
The vendor request allows the host to read arbitrary memory addresses, which is a serious… · New
Previously, a failed PRE_START trigger aborted the start. Now the function logs the error but… · New
This UUID does not match the usb_audio UUID added to uuid-registry.txt (9a84b5e2-...). Since… · New
These new globals are introduced unconditionally and exported with generic names, increasing global… · New
Directly forcing c->state and pipe->status bypasses the normal component/pipeline state machine… · New
Byte-by-byte ring-buffer copies with modulo in the loop add significant overhead on MCUs,… · New
Determining playback vs capture using pipeline_id/id is fragile and can mis-route global… · New
This change gates the syscall declaration on CONFIG_USERSPACE but does not add a… · New

What changed in this PR

Adds initial SOF + Zephyr platform support for Raspberry Pi RP2350 (Pico 2) and introduces a UAC2-based static audio pipeline with USB streaming.

Changes:

Introduces a new rp2350 platform (init/clock/mailbox stubs) and Zephyr build glue.
Adds a USB audio component plus RP2350 static topology and UAC2 control/callback plumbing.
Adds non-userspace (!CONFIG_USERSPACE) compatibility guards for various Zephyr syscall-based APIs.

File	Description
`zephyr/CMakeLists.txt`	Adds RP2350 platform selection and build dependencies/includes.
`src/platform/rp2350/*`	New RP2350 platform implementation, headers, clock init, and static topology definition.
`src/audio/usb_audio.c` / `src/include/sof/audio/usb_audio.h`	New USB audio component with a ring buffer bridging UAC2 and SOF pipelines.
`src/audio/pipeline/static_pipeline_loader.c`	Adds failure-stage diagnostics and changes pipeline start/stop/reset behavior.
`src/audio/pipeline/sof_static_pipeline.c` / `src/include/sof/audio/pipeline/sof_static_pipeline.h`	Adds UAC2 ops + static pipeline runtime integration (esp/teensy/rp2350).
`app/src/main.c` / `app/src/usbd_init.c`	Initializes static pipelines + UAC2 ops, and adds vendor diagnostic requests.
Various `src/include/` and `zephyr/include/`	Adds `CONFIG_USERSPACE` guards and fallback stubs for some syscall APIs.

_{Review effort: Lite}

+int main(int argc, char *argv[])
 {
+	ARG_UNUSED(argc);
+	ARG_UNUSED(argv);


+static struct net_buf *rp2350_peek_to_host(const struct usbd_context *const ctx,
+					   const struct usb_setup_packet *const setup)
+{
+	uint32_t addr = (setup->wIndex << 16) | setup->wValue;
+	uint16_t len = MIN(setup->wLength, 64);
+	if (!len) return NULL;
+	struct net_buf *buf = usbd_ep_ctrl_data_in_alloc(ctx, len);
+	if (!buf) return NULL;
+	net_buf_add_mem(buf, (const void *)addr, len);
+	return buf;
+}


@@ -1916,7 +1958,20 @@ int sof_static_pipeline_start(uint32_t pipeline_id)
 		int ret = pipeline_trigger_run(pipe, dev, COMP_TRIGGER_PRE_START);
 		if (ret < 0) {
 			LOG_ERR("Pipeline %u pre-start trigger failed: %d", pipeline_id, ret);


+/* UUID for USB Audio Component */
+/* b95039f6-3d23-41a4-9276-2fbb27c62d01 */
+#define SOF_USB_AUDIO_UUID \
+	DECLARE_SOF_RT_UUID("usb_audio", 0xb95039f6, 0x3d23, 0x41a4, \
+			    0x92, 0x76, 0x2f, 0xbb, 0x27, 0xc6, 0x2d, 0x01)


+int g_topo_fail_stage = 0;
+int g_topo_fail_item = 0;
+int g_topo_fail_code = 0;


+		if (pipe->status != COMP_STATE_READY) {
+			if (s_active_topo) {
+				for (size_t j = 0; j < s_active_topo->num_comps; j++) {
+					if (s_active_topo->comps[j].pipeline_id == pipeline_id) {
+						struct comp_dev *c = sof_static_comp_get(s_active_topo->comps[j].id);
+						if (c) {
+							comp_reset(c);
+							c->state = COMP_STATE_READY;
+						}
+					}
+				}
 			}
+			pipeline_reset(pipe, dev);
+			pipe->status = COMP_STATE_READY;
+		}


+	for (size_t i = 0; i < bytes; i++) {
+		ring->buf[ring->head] = s[i];
+		ring->head = (ring->head + 1) % USB_AUDIO_RING_BUFFER_SIZE;
+	}


+	if (config->pipeline_id == 1 || config->id == 1) {
+		g_playback_data = uad;
+	} else {
+		g_capture_data = uad;
+	}


+#if defined(__ZEPHYR__) && defined(CONFIG_SOF_FULL_ZEPHYR_APPLICATION) && defined(CONFIG_USERSPACE)
 __syscall int lib_manager_free_module(const uint32_t component_id);

 #include <zephyr/syscalls/lib_manager.h>


lrgirdwo added 3 commits November 10, 2026 15:38

app: boards: rpi_pico2: switch to picolibc and tune UDC buffers

90e0d11

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

lgirdwood requested a balanced review from Copilot November 10, 2026 15:58

lgirdwood commented Nov 10, 2026

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WIP: rp2350: add Raspberry Pi RP2350 (Pico 2) platform support and UAC2 audio streaming - #11438

WIP: rp2350: add Raspberry Pi RP2350 (Pico 2) platform support and UAC2 audio streaming#11438
lgirdwood wants to merge 3 commits into
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lgirdwood commented Nov 10, 2026

Summary

Key Changes

1. RP2350 Platform Support (src/platform/rp2350/ & app/boards/rpi_pico2/)

2. Audio Processing & Static Pipelines (src/audio/ & src/platform/rp2350/rp2350_pipeline_def.c)

3. Zephyr Application & Compatibility (app/ & zephyr/)

Hardware Verification & Test Results

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1. RP2350 Platform Support (`src/platform/rp2350/` & `app/boards/rpi_pico2/`)

2. Audio Processing & Static Pipelines (`src/audio/` & `src/platform/rp2350/rp2350_pipeline_def.c`)

3. Zephyr Application & Compatibility (`app/` & `zephyr/`)