Switched back to idf v4.2 and the problem appears to be fixed

This is still happening on a variety of different boards. By adding logging to cpu_start.c I've narrowed it down: the call to bootloader_flash_clock_config in call_start_cpu0 seems to be causing a problem.

ESP_EARLY_LOGI(TAG, "test 1.");

#if CONFIG_IDF_TARGET_ESP32
#if !CONFIG_SPIRAM_BOOT_INIT ...

My code uses HSPI to read an external ADC, but it never gets there.

After looking through cpu_start.c, I suspect that both cpus are setting s_cpu_up to true.

The app cpu sets s_cpu_inited[1] = true, and then sits in a loop waiting for s_cpu_inited[0] == true.

But call_start_cpu0 never gets to the ...

Esp32 endlessly reboots after flashing. Anyone have advice?

Monitor output:

...
Writing at 0x00074000... (96 %)
Writing at 0x00078000... (100 %)
Wrote 693056 bytes (439172 compressed) at 0x00010000 in 9.8 seconds (effective 563.0 kbit/s)...
Hash of data verified.

Leaving...
Hard resetting via ...