Takes too long until image is displayed on lcd (on STM32F769NI)

[Phyo .1]

Hello,

Here's my enviroment;

STM32F769Ni Custom board : SDRAM(IS42S32800G-6BLI) + NOR Flash(M29W128GL70ZA6E) + 800 * 480 TFT LCD(RGB-24Bit parallel interface) + FreeRTOS (CMSIS_V2) + TouchGFX

It takes more then 20 second until LCD screen is displayed after power on.

Here's what i tried

1) changed setting to use internal flash for image(from external nor flash) -> same problem, takes too long until image is displayed on lcd.

2) disabled FMC Bank1 (refer to ST Document (AN4861 : LCD-TFT display controller(LTDC) on STM32MCUs)4.6.1 : Disable FMC bank1 if not used) -> still slow

3) copy image to frame buffer directly instead of using gfx generated widget -> in this case, lcd displayed quickly.

Is there somthing I need to check / setting to try for this problem or document I can refer?

Thanks.