8.7. microblaze (MicroBlaze)¶

8.7.1. KCU105 QEMU¶

The basic hardware initialization is performed by the BSP. This BSP supports the QEMU emulated Xilinx AXI Interrupt Controller v4.1.

8.7.1.1. Boot via ELF¶

The executable image is booted by QEMU in ELF format.

8.7.1.2. Clock Driver¶

The clock driver supports the QEMU emulated Xilinx AXI Timer v2.0. It is implemented as a simple downcounter. If device tree support is enabled in the build configuration, the clock driver will use the node that is compatible with xlnx,xps-timer-1.00.a from the device tree to configure the clock. The following device tree node properties are used to configure the clock driver: reg, clock-frequency, and interrupts.

8.7.1.3. Console Driver¶

The console driver supports the QEMU emulated Xilinx AXI UART Lite v2.0. It is initialized to a baud rate of 115200. If device tree support is enabled in the build configuration, the console driver will use the node that is compatible with xlnx,xps-uartlite-1.00.a from the device tree to configure the console. The following device tree node properties are used to configure the console driver: reg, status, port-number, and interrupts.

8.7.1.4. Network Driver¶

Support for networking is provided by the libbsd library. Network interface configuration is extracted from the device tree binary which, by default, is in <bsp/microblaze-dtb.h>. The device tree source for the default device tree is at dts/system.dts.

To replace the default device tree with your own, assuming my_device_tree.dts is the name of your device tree source file, first you must convert your device tree to .dtb format.

$ dtc -I dts -O dtb my_device_tree.dts > my_device_tree.dtb

The device tree blob, my_device_tree.dtb, can now be converted to a C file. The name system_dtb is significant as it is the name expected by the BSP.

$ rtems-bin2c -C -A 8 -N system_dtb my_device_tree.dtb my_dtb

The BSP_MICROBLAZE_FPGA_DTB_HEADER_PATH BSP configuration option can then be set to the path of the resulting source file, my_dtb.c, in the waf INI file to include it in the BSP build.

BSP_MICROBLAZE_FPGA_DTB_HEADER_PATH = /path/to/my_dtb.c

8.7.1.5. QSPI NOR JFFS2 Driver¶

The QSPI NOR JFFS2 driver supports the QEMU emulated n25q512a11 QSPI NOR flash device. It is initialized to a page size of 256 bytes and a sector size of 64 KiB. If device tree support is enabled in the build configuration, the QSPI NOR JFFS2 driver will use the node that is compatible with xlnx,xps-spi-2.00.a from the device tree to configure the QSPI NOR JFFS2 driver. The following device tree node properties are used to configure the QSPI NOR JFFS2 driver: reg and interrupts.

8.7.1.6. Running Executables¶

A .dtb (device tree blob) file should be provided to QEMU via the -hw-dtb option. In the example command below, the device tree blob comes from the Xilinx Petalinux KCU105 MicroBlaze BSP (https://www.xilinx.com/support/download/index.html/content/xilinx/en/downloadNav/embedded-design-tools.html).

Executables generated by this BSP can be run using the following command:

$ qemu-system-microblazeel -no-reboot -nographic -M microblaze-fdt-plnx -m 256 \
 -serial mon:stdio -display none -hw-dtb system.dtb -kernel example.exe

8.7.1.7. Debugging with QEMU¶

To debug an application, add the option -s to make QEMU listen for GDB connections on port 1234. Add the -S option to also stop execution until a connection is made.

For example, to debug the hello sample and break at Init, first start QEMU.

$ qemu-system-microblazeel -no-reboot -nographic -M microblaze-fdt-plnx -m 256 \
 -serial mon:stdio -display none -hw-dtb system.dtb -kernel \
 build/microblaze/kcu105_qemu/testsuites/samples/hello.exe -s -S

Then start GDB and connect to QEMU.

$ microblaze-rtems6-gdb build/microblaze/kcu105_qemu/testsuites/samples/hello.exe
(gdb) target remote localhost:1234
(gdb) break Init
(gdb) continue

8.7.2. KCU105¶

The basic hardware initialization is performed by the BSP. This BSP supports the Xilinx AXI Interrupt Controller v4.1.

This BSP was tested using the Xilinx Kintex UltraScale FPGA KCU105 board configured with the default Petalinux KCU105 MicroBlaze BSP. The defaults may need to be adjusted using BSP configuration options to match the memory layout and configuration of your board.

8.7.2.1. Clock Driver¶

The clock driver supports the Xilinx AXI Timer v2.0. It is implemented as a simple downcounter. If device tree support is enabled in the build configuration, the clock driver will use the node that is compatible with xlnx,xps-timer-1.00.a from the device tree to configure the clock. The following device tree node properties are used to configure the clock driver: reg, clock-frequency, and interrupts.

8.7.2.2. Console Driver¶

The console driver supports the Xilinx AXI UART Lite v2.0. It is initialized to a baud rate of 115200. If device tree support is enabled in the build configuration, the console driver will use the node that is compatible with xlnx,xps-uartlite-1.00.a from the device tree to configure the console. The following device tree node properties are used to configure the console driver: reg, status, port-number, and interrupts.

8.7.2.3. Debugging¶

The following debugging procedure was used for debugging RTEMS applications running on the Xilinx KCU105 board using GDB.

First send an FPGA bitstream to the board using OpenOCD.

$ openocd -f board/kcu105.cfg -c "init; pld load 0 system.bit; exit"

After the board has been programmed, start the Vivado hw_server application to serve as the debug server. Leave it running in the background for the rest of the process.

$ tools/Xilinx/Vivado/2020.2/bin/hw_server

With the debug server running, connect to the debug server with GDB, load the application, and debug as usual. By default the GDB server listens on port 3002.

$ microblaze-rtems6-gdb example.exe
(gdb) target extended-remote localhost:3002
(gdb) load
(gdb) break Init
(gdb) continue