## Step 3: Create the Vitis Platform
Vitis Platform can be created with Vitis GUI or XSCT command line. This tutorial will focus on GUI flow.
### Prepare for Platform Packaging
We would store all the necessary files in one directory for Vitis platform creation flow.
Required platform creation source files
| Component | Conventional Path or Filename | Description |
| --------------------------------------------- | ----------------------------------------------------- | ------------------------------------------------------------- |
| Boot components in BOOT.BIN | boot/bl31.elfboot/u-boot.elfboot/system.dtb | All components referred in linux.bif should be in this folder |
| Boot components in FAT32 partition of SD Card | image/boot.scr | U-boot configuration file |
Optional platform creation source files
| Component | Conventional Path or Filename | Description |
| --------------------------------- | ---------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| BOOT Image Description file (BIF) | boot/linux.bif | BIF describes the layout of BOOT.BIN. Vitis can generate a default BIF for general purpose usage. User can provide customized BIF when needed. |
| Linux Software Components | sw_comp/Imagesw_comp/rootfs.ext4sw_comp/sysroots | Linux components for application creation and Linux booting. They can be packaged into platform or stay standalone and be linked during application creation process. |
Linux software components can be reused in most cases when platform hardware design changes. So we will not package them into the platform. Here we prepare them for application creation in the next step.
We would store all the necessary files for Vitis platform creation flow. Here we call it **step3_pfm** directory. Example files can be found in **ref_files/step3_pfm** directory of this repository.
1. Prepare the boot components and store them in the same directory. They are generated by PetaLinux and originally located in **/images/linux** directory. You can copy them into **step3_pfm/boot** for easy understanding. Here we keep them in **/images/linux** directory because in case we need to update PetaLinux settings and rebuilt PetaLinux, we just need to clean platform and rebuilt them in Vitis to generate a new platform. We won't need to copy them manually every time. These files are the source of creating final BOOT.BIN during application packaging. When creating the platform, these files will be copied to the platform output directory.
- bl31.elf
- u-boot.elf
- system.dtb
2. Prepare **step3_pfm/sd_dir** directory. Contents in this directory will be packaged to FAT32 partition of SD card image by v++ package tool.
- Copy **boot.scr** from **/images/linux directory** to the **step3_pfm/sd_dir** directory. It's a script for u-boot initialization. U-boot will read it from fat32 partition during boot process.
3. Prepare Linux software components for application creation. Platform packaging can add them or exclude them. Due to the software component size, they are usually kept outside of platforms so that these components can be reused among multiple platforms with the same architecture. On the other side, keeping Linux software components in the platform can prevent mix and match different combinations when delivering the platform from one team to another. Here we keep the Linux software components standalone.
```bash
# Create sw_comp directory
cd step3_pfm
mkdir sw_comp
cd sw_comp
# Copy Linux kernel image
cp /images/linux/Image .
# Copy EXT4 Root Filesystem
cp /images/linux/rootfs.ext4 .
# Install sysroot to this directory
/images/linux/sdk.sh -d ./ -y
```
Finally, your prepared directory structure looks like this.
```
tree -L 3 --charset ascii
.
|-- boot
| |-- bl31.elf
| |-- system.dtb
| `-- u-boot.elf
|-- sd_dir
| `-- boot.scr
|-- sw_comp
| |-- environment-setup-cortexa72-cortexa53-xilinx-linux
| |-- Image
| |-- rootfs.ext4
| |-- site-config-cortexa72-cortexa53-xilinx-linux
| |-- sysroots
| | |-- cortexa72-cortexa53-xilinx-linux
| | `-- x86_64-petalinux-linux
| `-- version-cortexa72-cortexa53-xilinx-linux
```
> Note: If you run the fast track script, the boot directory only has linux.bif file because the platform creation script xsct_create_pfm.tcl uses /images/linux directory as boot directory for components of the BIF file. To make the GUI flow easier, we copy these components to boot directory for preparation.
### Platform Packaging
First we create a **Vitis platform project** with the **XSA file** generated by Vivado
1. Launch Vitis.
```bash
# You are still in step3_pfm directory
# Setup Vitis environment
source /settings64.sh
# Launch Vitis, using ./platform_repo directory as workspace
vitis -workspace ./platform_repo &
```
2. Create a platform project
- In the Vitis IDE, select **File > New > Platform Project** to create a platform project.
- Enter the project name. For this example, type `vck190_custom`, click **Next**.
- In the Platform page, click **Browse** button, select the XSA file generated by the Vivado. In this case, it is located in `/vck190_custom.xsa`. Click **Next**.
- Set the **operating system** to **linux**.
- Set the processor to **psv_cortexa72**.
- Click **Finish**.
3. Setup Linux domain settings in Platform Settings view.
- Click the **linux on psv_cortexa72** domain
- Update the **Display Name** to `xrt` by clicking the edit button on the right of this line and input the name. We'd like to indicate this is a Linux domain has XRT installed and is capable of running acceleration applications.
- Set **Bif file**: Click the drop down button and select **Generate BIF**. The generated BIF file is generated bin resource directory.
- **Boot Components Directory**: Browse to **step3_pfm/boot/** and click OK. Bootgen will look for boot components referred by BIF in this directory to generate BOOT.BIN
- **FAT32 Partition Directory**: Browse to **step3_pfm/sd_dir** and click OK. Files in this directory will be copied to FAT32 partition of SD card.
>Note: **FAT32 Partition Directory** option name was called Linux Image Directory in previous releases. It was defined when initramfs is used to boot Linux. In that case, the Linux kernel image, or image.ub with kernel image, rootfs and device tree are all placed in the FAT32 partition of the SD Card. Now with EXT4 rootfs, only boot.scr needs to be placed in the FAT32 partition. The option name is updated to reflect this change.
>Note: **Linux Rootfs** and **Sysroot Directory** are optional for Linux domain. They can be provided in either platform or application. We will add them in application creation phase because it would be easy to reuse these components among multiple platforms.
4. (Optional) Update Linux domain emulation settings
- Vitis IDE or XSCT sets QEMU Arguments and PMC QEMU Arguments to the default files in Vitis installation directory. These default settings should be able to boot Linux in QEMU properly. If you need to update the arguments, you can copy them to local, update and setup the new path in the Linux domain configuration.
- Set QEMU Data to **step3_pfm/boot** directory because QEMU may use some boot components.
5. Add AI Engine domain
- Click Add domain icon
- Set Name to **aiengine**
- Change OS to **aie_runtime**.
- Keep other settings to default and click **OK**.
Note: Vitis IDE and XSCT will add QEMU arguments for AI Engine domain automatically.
6. Click **vck190_custom** project in the Vitis Explorer view, click the **Build** button to generate the platform.
**Note: The generated platform is placed in the export directory. BSP and source files are also provided for re-building the FSBL and PMU if desired and are associated with the platform. The platform is ready to be used for application development.**
### Fast Track
Scripts are provided to package the Vitis platform.
To use these scripts, please run the following steps.
1. Run build
```
# cd to the step directory, e.g.
cd step3_pfm
make
```
2. To clean the generated files, please run
```bash
make clean
```
**[Next let's move to step 4 to try to build some applications on this platform and test them.](./step4.md)**
