Jetson/TX2 SPI

This how-to enables SPI in the kernel for Jetson TX2 with L4T R28.1 (JetPack 3.1). For the previous version see, Jetson/TX1 SPI.

Locating the SPI Pins
First, in the Jetson TX2 Developer Kit, the SPI pins are located on the J21 header - http://www.jetsonhacks.com/nvidia-jetson-tx2-j21-header-pinout/


 * Pin 19 - SPI(3) MOSI
 * Pin 21 - SPI(3) MISO
 * Pin 23 - SPI(3) CLK
 * Pin 24 - SPI(3) CS#0

Building SPIDev Module
It's suggested to enable support for SPIDev (userspace API).

To do that, we'll download the L4T kernel sources, enable SPIDev module in the kernel configuration, build and install the module.

Downloading the Kernel Sources
L4T source tarball available here: https://developer.nvidia.com/embedded/dlc/l4t-sources-28-1

JetsonHacks also has a script (https://github.com/jetsonhacks/buildJetsonTX2Kernel)

$ git clone http://github.com/jetsonhacks/buildJetsonTX2Kernel.git $ cd buildJetsonTX2Kernel $ ./getKernelSources.sh

The JetsonHacks script should have downloaded the kernel sources to the /usr/src/ folder.

Configuring the Kernel
Edit the  file:

$ cd /usr/src $ cd /kernel/kernel-4.4/ $ cd /arch/arm64/configs/ $ sudo gedit tegra18_defconfig

Add the following to just below CONFIG_SPI=y CONFIG_SPI_TEGRA114=y CONFIG_SPI_SPIDEV=m CONFIG_QSPI_TEGRA186=y

Building the Kernel
Generate the new  file after the changes to

$ cd /usr/src/kernel/kernel-4.4 $ sudo make tegra18_defconfig

Build the kernel modules:

$ cd ~/buildJetsonTX2Kernel $ sudo ./makeKernel.sh

Ensure the SPIDev Kernel module is copied to

$ sudo cp /usr/src/kernel/kernel-4.4/drivers/spi/spidev.ko /lib/modules/$(uname -r)/kernel/drivers/

Update module dependencies and kernel image:

$ sudo depmod $ sudo ./copyImage.sh

Reboot to new config: $ sudo reboot

Verifying SPIDev Module
To verify the SPIDev kernel module that we built is enabled, navigate to

$ cd /lib/modules/$(uname -r) $ cat modules.dep # print the contents of modules.dep to the screen, and ensure spidev.ko is in there # e.g. @line 23 # kernel/drivers/spi/spidev.ko

Modifying the Device Tree
Next, we must enable the SPI device in the Jetson's device tree.

To do this, we'll install the device tree compiler (DTC), modify the device tree source (DTS), and re-build the device tree binary (DTB).

Installing DTC Tool
First we need the

$ sudo apt-get update $ sudo apt-get install device-tree-compiler

Decompiling Device Tree
To obtain the device tree source (DTS) that we'll edit, first we need to decompile the current device tree binary (DTB) back to source:

$ cd /boot/dtb/ $ sudo dtc -I fs -O dts -o extracted_proc.dts /proc/device-tree

Update The Device-Tree
Use your text editor of choice to update the DTS that we decompiled above:

$ sudo gedit myTX2DeviceTreeSource.dts

Make the following patches:

spi@3240000{ compatible = "nvidia,tegra186-spi"; reg = <0x0 0x3240000 0x0 0x10000>; ....    ....     ....     linux,phandle = ; '''spi@0 { '''compatible = "spidev"; '''reg = ; '''spi-max-frequency = <0x1312D00>; '''nvidia,enable-hw-based-cs; '''nvidia,cs-setup-clk-count = ; '''nvidia,cs-hold-clk-count = ; '''nvidia,rx-clk-tap-delay = ; '''nvidia,tx-clk-tap-delau = ; '''};  };

Recompiling the Device Tree
Use DTC again to recompile the modifying DTS back into the new DTB:

$ cd /boot/dtb/ $ sudo dtc -I dts -O dtb -o tegra186-quill-p3310-1000-c03-00-base.dtb extracted_proc.dts

Enabling the New DTB
It's better flash the DTB by flash command instead of modify the extlinux due plugin manager will broken may cause unknow problem like break the network interface. Below is the command flash the DTB only. sudo ./flash.sh -r -k kernel-dtb jetson-tx2 mmcblk0p1

As in Jetson/TX2 DTB, enable FDT in

TIMEOUT 30 DEFAULT PRIMARY MENU TITLE p2771-0000 eMMC boot options LABEL primary MENU LABEL primary kernel LINUX /boot/Image '''FDT /boot/dtb/tegra186-quill-p3310-1000-c03-00-base.dtb APPEND ${cbootargs} root=/dev/mmcblk0p1 rw rootwait rootfstype=ext4

Reboot for the changes to take effect:

$ sudo reboot

Verifying SPIDev Device
To confirm the SPIDev module has loaded and created the SPI device, check if SPIdev is available in your  folder:

$ ls /dev/spi* $ /dev/spidev.3.0