I am trying to set pins P8.37 and P8.38 to UART mode as follow:
debian@beaglebone:~$ config-pin P8.38 uart
P8_38 pinmux file not found!
sudo: no askpass program specified, try setting SUDO_ASKPASS
Cannot write pinmux file: /sys/devices/platform/ocp/ocp*P8_38_pinmux/state
debian@beaglebone:~$ config-pin P8.37 uart
P8_37 pinmux file not found!
sudo: no askpass program specified, try setting SUDO_ASKPASS
Cannot write pinmux file: /sys/devices/platform/ocp/ocp*P8_37_pinmux/state
It seems that config-pin function is looking in the wrong directory for P8_37 and P8_38 as the pin mux file is located at “/sys/devices/platform/ocp/of_node” and not at “ls /sys/devices/platform/ocp/”. The following prove my statement:
$ ls /sys/devices/platform/ocp/of_node
#address-cells mcasp@4803C000 P8_24_pinmux P9_15_pinmux serial@44e09000
aes@53500000 mmc@47810000 P8_25_pinmux P9_16_pinmux serial@48022000
can@481cc000 mmc@48060000 P8_26_pinmux P9_17_pinmux serial@48024000
can@481d0000 mmc@481d8000 P8_27_pinmux P9_18_pinmux serial@481a6000
cape-universal name P8_28_pinmux P9_19_pinmux serial@481a8000
compatible ocmcram@40300000 P8_29_pinmux P9_20_pinmux serial@481aa000
edma@49000000 P8_03_pinmux P8_30_pinmux P9_21_pinmux sgx@56000000
elm@48080000 P8_04_pinmux P8_31_pinmux P9_22_pinmux sham@53100000
emif@4c000000 P8_05_pinmux P8_32_pinmux P9_23_pinmux #size-cells
epwmss@48300000 P8_06_pinmux P8_33_pinmux P9_24_pinmux spi@48030000
epwmss@48302000 P8_07_pinmux P8_34_pinmux P9_25_pinmux spi@481a0000
epwmss@48304000 P8_08_pinmux P8_35_pinmux P9_26_pinmux spinlock@480ca000
ethernet@4a100000 P8_09_pinmux P8_36_pinmux P9_27_pinmux ti,hwmods
gpio@44e07000 P8_10_pinmux P8_37_pinmux P9_28_pinmux timer@44e31000
gpio@4804c000 P8_11_pinmux P8_38_pinmux P9_29_pinmux timer@48040000
gpio@481ac000 P8_12_pinmux P8_39_pinmux P9_30_pinmux timer@48042000
gpio@481ae000 P8_13_pinmux P8_40_pinmux P9_31_pinmux timer@48044000
gpmc@50000000 P8_14_pinmux P8_41_pinmux P9_41_pinmux timer@48046000
i2c@44e0b000 P8_15_pinmux P8_42_pinmux P9_42_pinmux timer@48048000
i2c@4802a000 P8_16_pinmux P8_43_pinmux P9_91_pinmux timer@4804a000
i2c@4819c000 P8_17_pinmux P8_44_pinmux P9_92_pinmux tptc@49800000
interrupt-controller@48200000 P8_18_pinmux P8_45_pinmux phandle tptc@49900000
l4_wkup@44c00000 P8_19_pinmux P8_46_pinmux pruss@4a300000 tptc@49a00000
lcdc@4830e000 P8_20_pinmux P9_11_pinmux pruss_soc_bus@4a326000 tscadc@44e0d000
linux,phandle P8_21_pinmux P9_12_pinmux ranges usb@47400000
mailbox@480C8000 P8_22_pinmux P9_13_pinmux rng@48310000 wdt@44e35000
mcasp@48038000 P8_23_pinmux P9_14_pinmux rtc@44e3e000
Further, this are info of my system and setup:
Image I used: Debian 9.3 2018-03-05 4GB SD IoT
debian@beaglebone:~$ cat /boot/uEnv.txt
#Docs: http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0
uname_r=4.9.82-ti-r102
#uuid=
#dtb=
###U-Boot Overlays###
###Documentation: http://elinux.org/Beagleboard:BeagleBoneBlack_Debian#U-Boot_Overlays
###Master Enable
enable_uboot_overlays=1