## Step 2: Create the Software Components with PetaLinux
In this step, we'll create a PetaLinux project that includes Vitis Platform required components.
### Create the PetaLinux Project
1. Setup PetaLinux environment: `source /settings.sh`
2. Create PetaLinux Project with XSA we created in previous step
```bash
petalinux-create -t project --template versal --force -n petalinux
cd petalinux
petalinux-config --get-hw-description= --silentconfig
```
- The created PetaLinux project name is **petalinux**. Please feel free to change the PetaLinux project name with **petalinux-create -n** option.
3. Apply VCK190 device tree
- Run `petalinux-config`
- Go to **DTG Settings**
- Enter **versal-vck190-reva-x-ebm-02-reva** for **MACHINE_NAME** option (Config option name is CONFIG_SUBSYSTEM_MACHINE_NAME)
Note: This preset device setting will add ethernet PHY info to device tree. The [device tree source code][1] will be applied to the PetaLinux project. If your VCK190 board version is different, please check the device tree source code directory whether it has a corresponding device tree version for your board and apply it in the PetaLinux project. You can clone the git repository, or use find file feature in github.
[1]: https://github.com/Xilinx/u-boot-xlnx/blob/master/arch/arm/dts/versal-vck190-revA-x-ebm-02-revA.dts
### Customize Root File System, Kernel, Device Tree and U-boot
1. Add user packages by appending the CONFIG_x lines below to the **/project-spec/meta-user/conf/user-rootfsconfig** file.
**Note: This step is not a must but it makes it easier to find and select all required packages in next step.**
Packages for base XRT support (required):
```
CONFIG_packagegroup-petalinux-xrt
```
- XRT package group contains all the packages for Vitis acceleration runtime.
Packages for on-board acceleration application compiling support (optional):
```
CONFIG_packagegroup-petalinux-xrt-dev
```
- package names with `-dev` suffix means header files, dependency libraries and soft links required by compiling environment in Yocto.
Packages for easy system management (recommended):
```
CONFIG_dnf
CONFIG_e2fsprogs-resize2fs
CONFIG_parted
CONFIG_auto-login
```
- **dnf** is the package management tool
- **auto-login** will login as root by default. It's useful for development and debugging time. Please remove it at production phase.
- **parted** and **e2fsprogs-resize2fs** can expand the ext4 partition to use the rest of the SD card.
2. Run ```petalinux-config -c rootfs``` and select **user packages**, select name of rootfs all the libraries listed above, save and exit. If step1 is skipped, please use search function with `/` key to find these packages and enable them.
3. In rootfs config, go to **Image Features** and enable **package-management** and **debug_tweaks** option, store the change and exit. (Recommended)
- Exit from **user packages** to root configuration window by select **Exit** and press **Enter**.
- Select **Image Features** and enter.
- Enable **package-management** and **debug_tweaks** by pressing space key. Sub items of package-management is not needed.
- Exit
- Exit
- Save
4. Update the system-user device tree (required).
Append the following contents to the **project-spec/meta-user/recipes-bsp/device-tree/files/system-user.dtsi** file.
- **zyxclmm_drm** node is required by zocl driver, which is a part of XRT.
- **axi_intc_0** node defines 32 interrupt inputs. This can not be inferred by the hardware settings in Vivado. So we have to add it here manually.
- **Note**: an example file is provided in **ref_files/step2_petalinux/project-spec/meta-user/recipes-bsp/device-tree/files/system-user.dtsi**.
```
&amba {
zyxclmm_drm {
compatible = "xlnx,zocl-versal";
status = "okay";
interrupt-parent = <&axi_intc_0>;
interrupts = <0 4>, <1 4>, <2 4>, <3 4>,
<4 4>, <5 4>, <6 4>, <7 4>,
<8 4>, <9 4>, <10 4>, <11 4>,
<12 4>, <13 4>, <14 4>, <15 4>,
<16 4>, <17 4>, <18 4>, <19 4>,
<20 4>, <21 4>, <22 4>, <23 4>,
<24 4>, <25 4>, <26 4>, <27 4>,
<28 4>, <29 4>, <30 4>, <31 4>;
};
};
&axi_intc_0 {
xlnx,kind-of-intr = <0x0>;
xlnx,num-intr-inputs = <0x20>;
};
```
5. Add EXT4 rootfs support (Recommended)
PetaLinux uses **initrd** format for rootfs by default. This format extracts rootfs in DDR memory, which means it reduces the usable DDR memory for runtime and can't retain the rootfs changes after reboot. To enable the root file system to retain changes, we'll use EXT4 format for rootfs as the second partition on SD card while keep the first partition FAT32 to store other boot files.
- Run `petalinux-config`, go to **Image Packaging Configuration**, select **Root File System Type** as **EXT4**, and append `ext4` to **Root File System Formats**.
- Update bootargs to use ext4 partition as root file system in system-user.dtsi:
```
/ {
chosen {
stdout-path = "serial0:115200";
bootargs = "console=ttyAMA0 earlycon=pl011,mmio32,0xFF000000,115200n8 clk_ignore_unused root=/dev/mmcblk1p2 rw rootwait rootfs=ext4";
};
};
```
Note: `root=/dev/mmcblk1p2` is the rootfs path; `rootfs=ext4` defines the rootfs type. Please refer to the full system-user.dtsi in [ref_files/step2_petalinux/system-user.dtsi](ref_files/step2_petalinux/system-user.dtsi).
### Build PetaLinux Image
1. From any directory within the PetaLinux project, build the PetaLinux project.
```
petalinux-build
```
The generated u-boot and Linux images will be located in **images/linux** directory.
2. Build and install sysroot
```
petalinux-build --sdk
```
Sysroot **sdk.sh** will be generated in **images/linux** directory. We will extract it in next step.
### Fast Track
Scripts are provided to re-create PetaLinux project and generate outputs. To use these scripts, please run the following steps.
1. Run build
```
# cd to the step directory, e.g.
cd step2_petalinux
make
```
2. To clean the generated files, please run
```bash
make clean
```
**Note: Now HW platform and SW platform are all generated. Next we would [package the Vitis Platform](./step3.md).**
