Due to the boot flow differences between KV260 and base platforms for Xilinx evaluation boards like ZCU104, platform developer needs to prepare one additional DTBO file besides the normal software components for Vitis platforms because application developers needs to add this DTBO file to the application deployment package. The other software components generation flow is similar to the flow described in the [ZCU104 tutorial](../../Introduction/02-Edge-AI-ZCU104/step2.md). Since KV260 provides its BSP, we can use the PetaLinux BSP to generate Linux kernel, root file system and boot components, or do more customization based on the BSP.
# Step 2: Create the Software Components with PetaLinux
KV260 provides an off-the-shelf boot image and has its enhanced boot sequence. Since the image can boot successfully out of the box, Vitis platform developers can skip some software component preparation steps for Linux booting.
### Generating Normal Software Components from the KV260 Starter Kit BSP
1. Check [Kria K26 SOM wiki](https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/1641152513/Kria+K26+SOM). Download the **Starter Kit SOM BSP** that matches your tool version under **PetaLinux Board Support Package** section.
For example, https://www.xilinx.com/member/forms/download/xef.html?filename=xilinx-k26-starterkit-v2021.1-final.bsp
Save it to your working directory.
2. Setup PetaLinux environment
```bash
source /settings.sh
```
3. Update PetaLinux eSDK to enable the recipes needed by the Starter Kit SOM BSP.
```bash
petalinux-upgrade -u 'http://petalinux.xilinx.com/sswreleases/rel-v2021/sdkupdate/2021.1_update1/' -p 'aarch64'
```
4. Create PetaLinux with the Starter Kit SOM BSP and the XSA export from step 1.
```bash
petalinux-create --type project -s xilinx-k26-starterkit-v2021.1-final.bsp
cd xilinx-k26-starterkit-v2021.1
petalinux-config --get-hw-description=
```
5. Add XRT to rootfs
KV260 PetaLinux BSP doesn't enable XRT because it installs XRT with overlay. To create sysroot for application developer cross compiling, we enable XRT in the rootfs.
- Run `petalinux-config -c rootfs` to launch rootfs configruation window.
- Go to **Filesystem packages -> libs -> xrt**
- Enable `xrt`
- Press Exit to exit configrution. Press Save to save the configuration.
6. Build PetaLinux and generate SDK
```bash
petalinux-build
petalinux-build --sdk
```
The PetaLinux image files and sysroot sdk.sh will be generated in /images/linux directory. We will use them in the next step.
## Generate Device Tree Overlay
Since KV260 loads PL after Linux boots up, the PL IP information in the platform needs to be loaded dynamicly as device tree overlay. So one additional requirement for KV260 acceleration platform software is to generate the device tree overlay for the platform PL IPs. This device tree overlay serves two purposes:
1. It needs to have ZOCL node so that XRT driver can be loaded properly
2. It can include any configurations of the PL IP in the platform logic designed in step 1.
The device tree information for PL in your application is loaded after Linux boot together with the PL bitstream. A device tree overlay (DTBO) can be loaded and unloaded in Linux. For more information about DTBO, please refer to https://lkml.org/lkml/2012/11/5/615.
Xilinx provides Device Tree Generator (DTG) to generate device tree from XSA file exported from Vivado. DTG is configurable for which information to be generated. According to our requirement, we will use these two options:
- `CONFIG.dt_zocl`: Generate ZOCL device tree node for XRT
- `CONFIG.dt_overlay`: Add overlay properties in dtsi for DTBO generation
Run the following steps to generate DTBO from XSA
1. Install DTG
```bash
git clone https://github.com/Xilinx/device-tree-xlnx
cd device-tree-xlnx
git checkout xlnx_rel_v2021.1
```
2. Generate DTS from XSA with XSCT.
- Launch XSCT
```bash
xsct
```
- Use XSCT HSI commands to read XSA and generate DTS.
```bash
hsi open_hw_design
hsi set_repo_path
hsi create_sw_design device-tree -os device_tree -proc psu_cortexa53_0
hsi set_property CONFIG.dt_overlay true [hsi::get_os]
hsi set_property CONFIG.dt_zocl true [hsi::get_os]
hsi generate_target -dir
hsi close_hw_design [hsi current_hw_design]
```
3. Compile the dtsi to dtbo.
```bash
dtc -@ -O dtb -o pl.dtbo pl.dtsi
```
### Next Step
> Note: Now HW platform and SW platform are all generated. Next we would [package the Vitis Platform](step3.md).
