fix(arch/otg): unmask WKUP so USB resume reaches the class driver

[dakejahl]

Summary

Fixes PX4/PX4-Autopilot#28340

The Synopsys DWC2-derived USB device drivers enable USBSUSP in GINTMSK but not WKUP, and every one of them ANDs GINTSTS with GINTMSK at the top of its ISR before dispatching. The WKUP branch and the *_resumeinterrupt() it calls are therefore dead code: CLASS_SUSPEND is delivered, CLASS_RESUME never is.

For CDC/ACM the asymmetry is fatal rather than merely lossy. cdcacm_suspend() calls uart_connected(&priv->serdev, false), and from then on serial.c refuses every board-side open() and write() with -ENOTCONN. The cdcacm_resume() that would call uart_connected(true) never runs, so the port stays unusable for the rest of the boot even though the device remains enumerated and the host has long since resumed it.

Adding WKUP to the mask makes the existing handler reachable. The status bit is already acknowledged in the same read/ack cycle as the rest of the writable interrupts, so unmasking it cannot latch.

The host-side check used to characterise this is in review for nuttx-ntfc-testing: apache/nuttx-ntfc-testing#4

Impact

Affects any board whose USB device controller is one of these eight drivers and whose host suspends it. Linux hosts do that by default: with power/control=auto and the usual autosuspend_delay_ms=2000, closing the tty is enough. Software that opens, reads and closes the port — as opposed to holding it open — kills the link on the first close, which is why this reads as an intermittent wedge rather than a deterministic bug.

No configuration, API or wire-format change. One extra interrupt source per suspend/resume, handled by code already present.

Drivers touched:

arch/arm/src/at32/at32_otgfsdev.c
arch/arm/src/common/stm32/stm32_otgfsdev_m3m4_v1.c
arch/arm/src/common/stm32/stm32_otghsdev_m3m4_v1.c
arch/arm/src/efm32/efm32_usbdev.c
arch/arm/src/stm32f7/stm32_otgdev.c
arch/arm/src/stm32h7/stm32_otgdev.c
arch/arm/src/stm32l4/stm32l4_otgfsdev.c
arch/xtensa/src/esp32s3/esp32s3_otg_device.c

Testing

Host: Linux 7.0.0-28-generic x86_64, xhci_hcd, usbcore.autosuspend=2.
Board: ARK FMU v6X (STM32H743), CONFIG_STM32H7_OTGFS=y, CONFIG_CDCACM=y (which selects SERIAL_REMOVABLE), NuttX 11.0.0 under PX4. Console on a separate STLINK-V3 VCP so it survives the CDC port dying.

Only the STM32H7 path was exercised on hardware. The other seven drivers carry a line-for-line copy of the same GINTMSK initialisation and the same masked-off resume handler.

Each cycle below forces a verified runtime suspend, resumes the device by opening the port, reads for 2 s, then asks the board over its console whether the CDC port is writable again.

Before:

device      /dev/serial/by-id/usb-ARK_ARK_FMU_v6X.x_0-if00 -> /dev/ttyACM1
usb         1-5.4  3185:0039  ARK FMU v6X.x
power       control=on autosuspend_delay_ms=2000 (restored on exit)

[1] suspended=True   read=12179   tail=0       board-side open failed: -ENOTCONN
[2] suspended=True   read=0       tail=0       board-side open failed: -ENOTCONN
[3] suspended=True   read=0       tail=0       board-side open failed: -ENOTCONN
[4] suspended=True   read=0       tail=0       board-side open failed: -ENOTCONN
[5] suspended=True   read=0       tail=0       board-side open failed: -ENOTCONN

cycles with a verified suspend: 5/5
of those, still streaming after resume: 0/5

FAIL: the link died after suspend and did not come back.

The 12179 bytes on the first cycle are the stale CONFIG_CDCACM_TXBUFSIZE=12000 TX buffer flushing on resume, not a working link — hence tail=0, the bytes seen in the last second of the window.

After:

[1] suspended=True   read=40898   tail=23316   board-side open ok
[2] suspended=True   read=42441   tail=22020   board-side open ok
[3] suspended=True   read=36945   tail=20372   board-side open ok
[4] suspended=True   read=44866   tail=22897   board-side open ok
[5] suspended=True   read=37565   tail=20480   board-side open ok

cycles with a verified suspend: 5/5
of those, still streaming after resume: 5/5

PASS: the link recovered from every suspend.

Board side on the unpatched build, after a single host suspend, the port is gone for good:

nsh> echo hi > /dev/ttyACM0
nsh: echo: open failed: Transport endpoint is not connected

Patched, the same command succeeds once the host resumes, and a 22 s suspend is followed by full recovery of the CDC stream (tx 21946 B/s, txerr 0.0 B/s, 217 kB read by the host over the following 10 s).

Build-tested beyond STM32H7: cubepilot_cubeyellow (stm32f7 OTGFS), airmind_mindpx-v2 (common/stm32 OTGFS), matek_gnss-m9n-f4 (common/stm32 OTGHS).

./tools/checkpatch.sh -c -u -m -g master..HEAD passes.

[github-actions]

MemBrowse Memory Report

No memory changes detected for:

• arduino-mega2560
• esp32-devkitc
• hifive1-revb
• mirtoo
• qemu-armv8a
• qemu-intel64
• rx65n-rsk2mb
• s698pm-dkit
• stm32-nucleo-f103rb