[Bug]: T-Beam S3 blocks during boot

[oseiler2]

Category

Hardware Compatibility, Serial

Hardware

T-Beam S3

Firmware Version

v2.3.5.2f9b68e

Description

T-Beam S3 devices can hang at boot until a serial connection is established on the USB CDC interface.
This was likely introduced by #3597
Also see #3597 (comment)

It hangs after the below logs for me. When I connect a serial on the USB CDC port it continues booting.

FWIW, I don't think it is necessarily related to this espressif/arduino-esp32#7554
I have checked all flush() calls on the relevant HWCDC and couldn't isolate the issue by doing so.

Relevant log output

ESP-ROM:esp32s3-20210327
Build:Mar 27 2021
rst:0x1 (POWERON),boot:0x8 (SPI_FAST_FLASH_BOOT)
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fce3808,len:0x3ac
load:0x403c9700,len:0x9b4
load:0x403cc700,len:0x28d8
entry 0x403c98bc
E (414) esp_core_dump_flash: No core dump partition found!
E (414) esp_core_dump_flash: No core dump partition found!
[  1304][I][esp32-hal-psram.c:96] psramInit(): PSRAM enabled

[geeksville]

This issue has been mentioned on Meshtastic. There might be relevant details there:

https://meshtastic.discourse.group/t/t-beam-wont-power-on-without-usb/12043/2