Accessing Gpios Via "Gpio" Device Labels; Exporting Pinmux For The L4T Linux Kernel; Porting U-Boot - Nvidia Jetson Nano Manual

Accessing GPIOs via "gpio" Device Labels

You can access GPIOs (routed to the 40-pin GPIO expansion header) via device labels
that begin with gpio. The file /sys/kernel/debug/gpio lists these labels.
For example, to access gpio-19, enter this command:
$ gpiofind SPI0_CS0
This command displays output like:
gpiochip0 19

Exporting Pinmux for the L4T Linux Kernel

The Linux kernel uses device tree files to define the pinmux configuration. You can
generate these files directly from the Excel spreadsheet.
To generate device tree files for your pinmux configuration
1. In the spreadsheet, click Generate DT.
2. Answer "yes" to the prompt that asks whether you wish to generate the DT files.
3. Provide the name of your board when prompted.
The device tree files are saved in the same location as the Excel spreadsheet. After the
file is generated, make sure that the file name matches the one you use in your kernel
code. Correct the file name if there is a mismatch. Later, you will copy the device tree
files into the Linux kernel source tree.

Porting U-Boot

Perform the following actions in the U-Boot source code to add support for your board.
1. Copy include/configs/ p3450-porg.h to include/configs/<board>.h.
2. Edit the set of enabled devices and features in <board>.h as appropriate for your
board. For example, you must change the following:
#define CONFIG_TEGRA_BOARD_STRING
3. Copy arch/arm/dts/tegra210-p3450-porg.dts to
arch/arm/dts/tegra210-<board>.dts.
4. Edit the set of enabled devices and their parameters (e.g. GPIO and IRQ IDs) in
tegra210-<board>.dts as appropriate for your board.
Jetson Nano Platform Adaptation and Bring-Up Guide
Platform Adaptation and Bring-Up
"NVIDIA P3450-Porg"
DA_09361-002 | 6