Hi @StephenYeh ,

You are using the flash related pins.
To the EVK QSPI, it is not use B port, so GPIO_SD_B1_03 maybe OK.
But, you use the GPIO_SD_B1_05, which is the DQS pin, it will influence the flexSPI communication.
Please check the datasheet:

If you use the DQS pin, configure to the looped back interrnally, and the flexspi clock frequency limit to 60Mhz.
Wish it helps you!
Best Regards,
kerry