Subject: Need Help: Failing to permanently disablie VDDSDIO 1.9V Boost on ESP32 (ESP-IDF v5.5.1)

[Yogesh]

Hi everyone,
I’m encountering a unique issue with my ESP32 setup and would appreciate any guidance.
In my design, GPIO23 (used as MOSI) is shared between the ESP32 and another host processor, which boots from an external SPI flash connected to the same bus. During a system-wide reset (which includes both the ESP32 and the host processor), the ESP32’s EN pin is held low via an external 10K pull-down resistor. The host processor must actively drive EN high to allow the ESP32 to boot.
The problem is that even when the ESP32 is held in reset, the VDDSDIO 1.9V boost seems to activate, altering the voltage levels on IO23. This interferes with the host processor’s boot sequence, likely due to the unexpected voltage on the shared SPI line.
It appears that the bootloader or internal configuration is overriding any software-based settings and enabling the VDDSDIO boost regardless of the EN pin state.
I’m looking for a way to permanently disable the VDDSDIO boost in ESP-IDF v5.5.1, possibly via eFuse settings or another method, to ensure that IO23 remains at a stable voltage during boot, even when the ESP32 is held in reset.

I had tried keeping
# CONFIG_BOOTLOADER_VDDSDIO_BOOST_1_8V is not set
# CONFIG_BOOTLOADER_VDDSDIO_BOOST_1_9V is not set
in sdkconfig.defaults, and even added copy of sdkconfig.locked to sdk config after esp-idf set target in GitHub CI action.
But after the build sdkconfig seem to be updated with
CONFIG_BOOTLOADER_VDDSDIO_BOOST_1_9V=y

Has anyone faced a similar issue or found a reliable solution? Any help or suggestions would be greatly appreciated!
Thanks in advance!