ttyACM device is created very late

[epsilontheta]

Describe the bug After booting the Beaglebone I see in dmesg that the USB device is detected properly after 4 seconds. Then it takes another 36 seconds until the ttyACM0 device is created under /dev. This is a problem if you have a service that expects the device to be created when it starts. It seems like this is a regression w.r.t. the Debian 9 image as this delay was not present back then.

[    3.659645] usb 1-1: new full-speed USB device number 2 using musb-hdrc
[    3.808575] usb 1-1: New USB device found, idVendor=1546, idProduct=01a9, bcdDevice= 1.00
[    3.808591] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[    3.808599] usb 1-1: Product: u-blox GNSS receiver
[    3.808606] usb 1-1: Manufacturer: u-blox AG - www.u-blox.com

[   40.782413] cdc_acm 1-1:1.0: ttyACM0: USB ACM device
[   40.826035] usbcore: registered new interface driver cdc_acm
[   40.826051] cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters

When replugging the device the ttyACM0 device is created instantly.

Describe how to reproduce the bug Plugin USB device before boot and turn on power.

REQUIRED INFORMATION Run this command and paste the output here:

eeprom:[A335BNLTBBG1BBG219102075]
model:[TI_AM335x_BeagleBone_Green]
dogtag:[BeagleBoard.org Debian Buster IoT Image 2020-04-06]
bootloader:[eMMC-(default)]:[/dev/mmcblk1]:[U-Boot 2019.04-00002-g07d5700e21]:[location: dd MBR]
UBOOT: Booted Device-Tree:[am335x-boneblack-uboot-univ.dts]
UBOOT: Loaded Overlay:[AM335X-PRU-RPROC-4-19-TI-00A0]
UBOOT: Loaded Overlay:[BB-ADC-00A0]
UBOOT: Loaded Overlay:[BB-BONE-eMMC1-01-00A0]
UBOOT: Loaded Overlay:[BB-I2C1-00A0]
UBOOT: Loaded Overlay:[BB-I2C2-00A0]
UBOOT: Loaded Overlay:[BB-SPIDEV1-00A0]
UBOOT: Loaded Overlay:[BB-UART4-00A0]
UBOOT: Loaded Overlay:[BB-UART5-00A0]
UBOOT: Loaded Overlay:[M-BB-BBG-00A0]
kernel:[4.19.94-ti-r42]
/boot/uEnv.txt Settings:
uboot_overlay_options:[enable_uboot_overlays=1]
uboot_overlay_options:[uboot_overlay_addr0=/lib/firmware/BB-UART4-00A0.dtbo]
uboot_overlay_options:[uboot_overlay_addr1=/lib/firmware/BB-UART5-00A0.dtbo]
uboot_overlay_options:[uboot_overlay_addr2=/lib/firmware/BB-I2C1-00A0.dtbo]
uboot_overlay_options:[uboot_overlay_addr3=/lib/firmware/BB-I2C2-00A0.dtbo]
uboot_overlay_options:[uboot_overlay_addr4=/lib/firmware/BB-SPIDEV1-00A0.dtbo]
uboot_overlay_options:[disable_uboot_overlay_video=1]
uboot_overlay_options:[disable_uboot_overlay_audio=1]
uboot_overlay_options:[uboot_overlay_pru=/lib/firmware/AM335X-PRU-RPROC-4-19-TI-00A0.dtbo]
uboot_overlay_options:[enable_uboot_cape_universal=0]
pkg check: to individually upgrade run: [sudo apt install --only-upgrade <pkg>]
pkg:[bb-cape-overlays]:[4.14.20210416.0-0~buster+20210416]
pkg:[bb-wl18xx-firmware]:[1.20210520.0-0~buster+20210520]
pkg:[kmod]:[26-1]
pkg:[librobotcontrol]:[1.0.5-git20200715.0-0~buster+20200716]
pkg:[firmware-ti-connectivity]:[20190717-2rcnee1~buster+20200305]
groups:[debian : debian adm kmem dialout cdrom floppy audio dip video plugdev users systemd-journal bluetooth netdev i2c gpio pwm eqep remoteproc admin spi iio docker tisdk weston-launch xenomai cloud9ide]
cmdline:[console=ttyO0,115200n8 bone_capemgr.uboot_capemgr_enabled=1 root=/dev/mmcblk1p1 ro rootfstype=ext4 rootwait coherent_pool=1M net.ifnames=0 lpj=1990656 rng_core.default_quality=100 quiet]
dmesg | grep remote
[   50.871253] remoteproc remoteproc0: wkup_m3 is available
[   51.207736] remoteproc remoteproc0: powering up wkup_m3
[   51.207768] remoteproc remoteproc0: Booting fw image am335x-pm-firmware.elf, size 217168
[   51.208251] remoteproc remoteproc0: remote processor wkup_m3 is now up
[   53.639686] remoteproc remoteproc1: 4a334000.pru is available
[   53.642001] remoteproc remoteproc2: 4a338000.pru is available
dmesg | grep pru
[   53.639686] remoteproc remoteproc1: 4a334000.pru is available
[   53.639852] pru-rproc 4a334000.pru: PRU rproc node pru@4a334000 probed successfully
[   53.642001] remoteproc remoteproc2: 4a338000.pru is available
[   53.642172] pru-rproc 4a338000.pru: PRU rproc node pru@4a338000 probed successfully
dmesg | grep pinctrl-single
[    0.941500] pinctrl-single 44e10800.pinmux: 142 pins, size 568
dmesg | grep gpio-of-helper
[    0.954776] gpio-of-helper ocp:cape-universal: ready
lsusb
Bus 001 Device 002: ID 1546:01a9 U-Blox AG 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
END

root@beaglebone:~# systemd-analyze blame
         31.960s generic-board-startup.service
         31.175s dev-mmcblk1p1.device
          4.066s loadcpufreq.service
          3.256s systemd-udev-trigger.service
          3.150s custom_a.service
          2.851s networking.service
          2.282s connman.service
          2.121s avahi-daemon.service
          2.013s ssh.service
          1.993s systemd-logind.service
          1.820s wpa_supplicant.service
          1.413s systemd-journald.service
          1.325s systemd-timesyncd.service
          1.277s dnsmasq.service
          1.136s custom_b.service
           916ms systemd-journal-flush.service
           915ms cpufrequtils.service
           898ms systemd-user-sessions.service
           896ms custom_c.service
           593ms user@0.service
           578ms systemd-update-utmp.service
           571ms systemd-remount-fs.service
           535ms save-time.service
           479ms sys-kernel-debug.mount
           446ms dev-mqueue.mount
           440ms systemd-tmpfiles-setup.service
           436ms systemd-modules-load.service
           429ms systemd-udevd.service
           411ms systemd-tmpfiles-setup-dev.service
           402ms systemd-update-utmp-runlevel.service
           396ms fake-hwclock.service
           382ms sys-fs-fuse-connections.mount
           382ms systemd-sysusers.service
           363ms systemd-sysctl.service
           334ms systemd-random-seed.service
           310ms kmod-static-nodes.service
           257ms sys-kernel-config.mount
           213ms systemd-tmpfiles-clean.service
           129ms user-runtime-dir@0.service
           115ms ifupdown-pre.service

[RobertCNelson]

Hi @epsilontheta , it's probally built as a module, change it to built-in should come up as soon as usb..

lsmod

Regards,

[epsilontheta]

Ah, good catch. I got the delay down to 8 seconds by creating /etc/modules-load.d/cdc_acm.conf and adding the module there. Thanks for your fast response!