from ESP32 Technical Reference Manual:
SPI_WP This bit determines the write-protection signal output when SPI is idle. 1: output high; 0: output low. (R/W)
Modifying this bit changes output level of WP pin but it is kept all the time high / low - it does not change during SPI transmission. Tried both with user transmission and flash transmission (flash_rdid) with no success.
Is it a hardware bug?