BOOTLOADER sequence of handling USB bridge (works)
ide_power_enable(true);
sleep(HZ/20);
ata_enable(false);
usb_enable(true);

/firmware/usb.c static inline void usb_slave_mode(_Bool on) sequence (doesn't work)
do { } while(0);
disk_unmount_all(); <- internal rockbox housekeeping
ata_soft_reset(); <- write reset command to the drive
ata_init(); <- ata_is_coldstart();
ata_device_init();
ata_enable(true)

ata_enable(0); <- ata_enable(false)
usb_enable(1); <- usb_enable(true)
cpu_idle_mode(1); <- cpu_idle_mode(true)