RK3288/RK3399 has three modes after startup: normal mode, loader mode, MASKROM mode
Normal mode: normal startup mode, this mode cannot flash firmware.
Generally, this is the mode when the board is powered on.
loader mode: flash firmware mode, this mode can flash various images.
Press and hold the recover button and then turn on the power, and enter this mode through the detection of bootloader/uboot
MASKROM mode: This mode is used to save bricked machines, such as bootloader/uboot cannot be started, and cannot enter the loader mode to download normally.
It is necessary to find the corresponding EMMC_CLKO and GND solder joints on the board, short circuit and power on to enter the MASKROM mode.
These points need to ask the manufacturer of the board.
Under 7.1,
checkkey is performed in the int board_fbt_key_pressed(void) function of the fastboot.c file. Here it is detected that boot_rockusb is set, so it prints out the rockusb key pressed and enters the loader state.
Then the boot_rockusb in the checkkey function is initialized as follows
key_rockusb.type = KEY_INT;
key_rockusb.key.ioint.name = "rockusb_key";
key_rockusb.key.ioint.gpio = (GPIO_BANK3 | GPIO_D1);
key_rockusb.key .ioint.flags = I