$ cat /sys/kernel/debug/gpio 
GPIOs 0-287, platform/1c20800.pinctrl, 1c20800.pinctrl:
 gpio-37  (?                   ) out hi
 gpio-38  (?                   ) in  lo
 gpio-39  (?                   ) in  lo
 gpio-40  (?                   ) out hi
 gpio-41  (?                   ) in  hi
 gpio-42  (?                   ) out lo
 gpio-81  (ril_reset           ) out lo
 gpio-82  (ril_nstandby        ) out lo
 gpio-129 (?                   ) in  lo
 gpio-163 (sysfs               ) out lo
 gpio-164 (sysfs               ) out lo
 gpio-165 (sysfs               ) out lo
 gpio-225 (wlan_regon          ) out lo
 gpio-232 (?                   ) out hi
 gpio-238 (?                   ) out hi
 gpio-245 (otg_id              ) in  hi
 gpio-247 (?                   ) out hi
 gpio-248 (?                   ) out hi
 gpio-249 (?                   ) out hi
 gpio-250 (sysfs               ) out lo
 gpio-251 (?                   ) out hi
 gpio-266 (1c12000.sdmmc cd    ) in  hi
 gpio-267 (1c0f000.sdmmc cd    ) in  lo
 gpio-270 (?                   ) out hi
 gpio-271 (sysfs               ) out lo

GPIOs 1024-1025, platform/axp22-gpio, axp-pinctrl:
$ 

如果/sys/kernel/debug/gpio文件不存在，需要先挂载（需要root权限）

$ mount -t debugfs debugfs /sys/kernel/debug