Доступные GPIO представлены на рисунках:

Контроллер GPIO в линуксе - gpiochip0:

[root@baikal_t1_uq7 ~]# cat /sys/kernel/debug/gpio 
gpiochip1: GPIOs 477-479, parent: platform/1f045000.gpio, 1f045000.gpio:
 gpio-477 (                    |status              ) out lo 
 gpio-479 (                    |spi0 CS0            ) out hi ACTIVE LOW

gpiochip0: GPIOs 480-511, parent: platform/1f044000.gpio, 1f044000.gpio:
 gpio-480 (                    )
 gpio-481 (                    )
 gpio-482 (ENA_CPU_I2C_0       )
 gpio-483 (                    )
 gpio-484 (                    )
 gpio-485 (                    )
 gpio-486 (                    )
 gpio-487 (                    )
 gpio-488 (                    )
 gpio-489 (                    )
 gpio-490 (                    )
 gpio-491 (                    )
 gpio-492 (                    )
 gpio-493 (                    )
 gpio-494 (                    )
 gpio-495 (                    )
 gpio-496 (                    )
 gpio-497 (                    )
 gpio-498 (                    )
 gpio-499 (                    )
 gpio-500 (                    )
 gpio-501 (                    )
 gpio-502 (                    )
 gpio-503 (                    )
 gpio-504 (                    )
 gpio-505 (                    )
 gpio-506 (                    )
 gpio-507 (                    |sysfs               ) out hi 
 gpio-508 (                    )
 gpio-509 (                    )
 gpio-510 (                    )
 gpio-511 (                    )