Need the sysfs numbers for gpio in the jetson Nano reference design

Autonomous Machines Jetson & Embedded Systems Jetson Nano
1

I am using the Jetson Nano reference design. I need to know the sysfs name for GPIOS to be able to access them using GPIO Sysfs Interface for Userspace.
I looked into the Jetson_Nano_Module_Pinmux_Config_templates.xlsm but could not figure out the GPIO names to use in sysfs.
example:
GPIO02 is 124 in SODIMM .
GPIO05 is 128
GPIO06 is 130
GPIO04 is 127
GPIO03 is 126

are these the value I need to use the access these gpio using gpio# for sysfs? like for GPIO02 I would use gpio124.

3

hello samir.alami,

you may disassembler the device tree (*.dtb) file into text file for quick checking of the signal name.
for example,
$ dtc -I dtb -O dts -o output.txt tegra210.dtb

please also check documentation, Accessing GPIOs via “gpio” Device Labels, for reference,
thanks

4

Hi Samir.alami,

This post may help you map between the various GPIO names and the Linux sysfs GPIO numbers.

Regards,
Greg

5

hi Greg,
I followed the instruction on the post but cannot figure out the BASE value they are referring to

  1. The last step is to examine /sys/kernel/debuig/gpio to find the BASE pin id value from the kernels point of view.
    the pinmux sheet has the following info about the gpios I am interested in:
    |GPIO02|124|GPIO_PH6|GPIO3_PH.06|vddio_spi|wake10||pd|GPIO3_PH.06
    |GPIO05|128|AP_WAKE_NFC|GPIO3_PH.07|vddio_spi|pd|GPIO3_PH.07
    |GPIO06|130|NFC_EN| GPIO3_PI.00|vddio_spi|pd|GPIO3_PI.00
    |GPIO04|127|NFC_INT| GPIO3_PI.01|vddio_spi|wake11||pd|GPIO3_PI.01
    |GPIO03|126|GPS_EN| GPIO3_PI.02|vddio_spi|pd|GPIO3_PI.02|

I got the offset for each gpio after I get the value value of the P (pat) number for each GPIO.
here are the offsets:
GPIO02 = 62
GPIO05 = 63
GPIO06 = 64
GPIO04 = 65
GPIO03 = 66

how to I get the base value?

6

hello samir.alami,

you may refer to kernel initial messages for the GPIO base.
for example,

$ dmesg | grep GPIOs
...
[    0.562454] gpiochip_setup_dev: registered GPIOs 0 to 255 on device: gpiochip0 (tegra-gpio)
[    0.615033] gpiochip_setup_dev: registered GPIOs 504 to 511 on device: gpiochip1 (max77620-gpio)
7

are you indicating that the base value that I am asking for is 0 for gpiochip0? which means the sysfs values for the GPIOs requested is
GPIO02 = 62
GPIO05 = 63
GPIO06 = 64
GPIO04 = 65
GPIO03 = 66.

8

hello samir.alami,

you may also check the header file for the calculation formulas,
i.e.
$L4T_Sources/r32.4.3/Linux_for_Tegra/source/public/kernel/kernel-4.9/include/dt-bindings/gpio/tegra-gpio.h

#define TEGRA_GPIO(port, offset) \
        ((TEGRA_GPIO_PORT_##port * 8) + offset)

let’s taking GPIO02 and GPIO06 for an example,
GPIO02 = GPIO3_PH.06 = ( 7 * 8 ) + 6 = 62
GPIO06 = GPIO3_PI.00 = ( 8 * 8 ) + 0 = 64

9

thanks. that worked.