Xilinx ZynqMP

8.1.4. Xilinx ZynqMP#

This BSP family supports the following variants:

  • zynqmp_qemu_ilp32

  • zynqmp_qemu

  • zynqmp_apu_ilp32

  • zynqmp_apu

  • zynqmp_cfc400x

Platform-specific hardware initialization is performed by ARM Trusted Firmware (ATF). Other basic hardware initialization is performed by the BSP. These BSPs support the GICv2 interrupt controller present in all ZynqMP systems. The zynqmp_apu BSP has been tested on zu2cg, zu3eg, and zu9cg chip variants and should also work on any other ZynqMP chip variant since the Processing Subsystem (PS) does not vary among chip variants other than the number of CPU cores available.

This BSP family has been tested on the following hardware:

  • Avnet UltraZed-EG SOM

  • Innoflight CFC-400X

  • Trenz TE0802

  • Xilinx ZCU102

8.1.4.1. Boot on QEMU#

The executable image is booted by Qemu in ELF format.

8.1.4.2. Boot on ZynqMP Hardware#

On ZynqMP hardware, RTEMS can be started at EL1, EL2, or EL3 by u-boot or directly as part of BOOT.bin. Regardless of the exception level at boot, RTEMS will drop to EL1 for execution. For quick turnaround during testing, it is recommended to use the u-boot BOOT.bin that comes with the PetaLinux prebuilts for the board in question.

Some systems such as the CFC-400X may require a bitstream to be loaded into the FPGA portion of the chip to operate as expected. This bitstream must be loaded before RTEMS begins operation since accesses to programmable logic (PL) memory space can cause the CPU to hang if the FPGA is not initialized. This can be performed as part of BOOT.bin or by a bootloader such as u-boot. Loading bitstreams from RTEMS has not been tested on the ZynqMP platform and requires additional libraries from Xilinx.

8.1.4.3. Hardware Boot Image Generation#

RTEMS expects some hardware initialization to be performed by ATF and expects the services it provides to be present, so this must be included when generating a direct-boot RTEMS BOOT.bin.

When booting via u-boot, RTEMS must be packaged into a u-boot image or booted as a raw binary since u-boot does not currently support ELF64 which is required for AArch64 ELF binaries.

8.1.4.4. Example: Booting a RTEMS image on the ZCU102 ZynqMP board#

This example will walk through the steps needed for booting RTEMS from a SD card on the ZCU102 ZynqMP board. The reference for setting up a SD card and obtaining pre-built boot images is here.

Hardware Setup#

Set the dip switch SW6 according to the table below. This will allow the board to boot from the SD card. Connect a Micro-USB cable to the USB UART interface J83. This is a quad USB UART interface which will show up on the development host computer as four different serial or tty devices. Use the first channel for the console UART. It should be set to 115k baud.

Dip Switch JW6

ON

OFF

OFF

OFF

Prepare a SD card with a bootable partition#

The goal is to have a bootable SD card with a partition that is formatted with the FAT file system. The file system will contain the boot artifacts including BOOT.bin and the u-boot image. The RTEMS image will be placed on this volume. To create the bootable SD card, follow the directions here.

Once you have the card formatted correctly, you need to place the files from this archive on the FAT partition. The following file was used for this example: xilinx-vck190-v2021.2-final.bsp

In order to download these files, you need to have a Xilinx account login. As an alternative, you can download a bootable image for Ubuntu 20.04 and write it to an SD card using a utility such as Balena Etcher or dd. The Ubuntu image is available here. Download the image for the Zynq Ultrascale+ MPSoC Development boards, uncompress it and write it to the SD card. This image creates multiple partitions, but we only need to use the FAT partition with the boot artifacts on it.

Verify that the board can boot from the SD card#

It is worth booting the board from the SD card before trying to boot RTEMS. Insert the card and power on the board. You should see the messages on the first console indicating the various boot loader stages and eventually the Linux kernel. The goal is to interrupt u-boot when given the chance to access the u-boot command prompt.

Build RTEMS with examples#

Build the RTEMS zynqmp_apu BSP. Use the ticker.exe sample which can be found in the directory:

build/aarch64/zynqmp_apu/testsuites/samples

Prepare the RTEMS image#

Prepare your RTEMS image to boot from u-boot with the following commands:

$ aarch64-rtems7-objcopy -Obinary ticker.exe ticker.bin
$ gzip -9 ticker.bin
$ mkimage -A arm64 -O rtems -T kernel -a 0x10000 -e 0x10000 -n RTEMS -d ticker.bin.gz rtems.img

Note: If the start address has been changed in the BSP configuration, you have to adapt the -a and -e parameters accordingly. To find out the start address of an application, aarch64-rtems6-nm ticker.exe | grep \ _start can be used. That will show the address of the _start symbol which is the value that has to be used for the two parameters.

Boot the RTEMS image#

Copy the prepared RTEMS image to the SD card and insert the SD crd in the ZCU102 board. Power on the board. When you see the prompt on the console to interupt u-boot, hit a key to bring up the u-boot command prompt. On the u-boot command prompt you can boot your RTEMS image:

Zynq-MP> fatload mmc 0:1 0x1000 rtems.img
Zynq-MP> bootm 0x1000

This is the entire boot sequence:

Pre-FSBL boot Started
Xilinx Zynq MP First Stage Boot Loader
Release 2020.2   Nov 18 2020  -  11:46:01
NOTICE:  ATF running on XCZU9EG/silicon v1/RTL5.1 at 0xfffea000
NOTICE:  BL31: v2.2(release):xilinx_rebase_v2.2_2020.1-10-ge6eea88b1
NOTICE:  BL31: Built : 12:28:45, Nov 17 2020

U-Boot 2020.01 (Jun 15 2021 - 14:24:32 +0000)

Model: ZynqMP ZCU102 Rev1.0
Board: Xilinx ZynqMP
DRAM:  4 GiB
PMUFW:  v1.1
EL Level:       EL2
Chip ID:        zu9eg
NAND:  0 MiB
MMC:   mmc@ff170000: 0
In:    serial@ff000000
Out:   serial@ff000000
Err:   serial@ff000000
Bootmode: SD_MODE1
Reset reason:   SOFT
Net:
ZYNQ GEM: ff0e0000, mdio bus ff0e0000, phyaddr 12, interface rgmii-id

Warning: ethernet@ff0e0000 (eth0) using random MAC address - 82:32:1d:80:d9:c9
eth0: ethernet@ff0e0000
Hit any key to stop autoboot:  0

ZynqMP> fatload mmc 0:1 0x1000 rtems.img
46669 bytes read in 27 ms (1.6 MiB/s)
ZynqMP> bootm 0x1000
## Booting kernel from Legacy Image at 00001000 ...
   Image Name:   RTEMS
   Image Type:   AArch64 RTEMS Kernel Image (gzip compressed)
   Data Size:    46605 Bytes = 45.5 KiB
   Load Address: 10000000
   Entry Point:  10000000
   Verifying Checksum ... OK
   Uncompressing Kernel Image
## Transferring control to RTEMS (at address 10000000) ...

*** BEGIN OF TEST CLOCK TICK ***
*** TEST VERSION: 7.8923d90.f381e9bab29278e4434b1a93e70d17a7562dc64c
*** TEST STATE: EXPECTED_PASS
*** TEST BUILD: RTEMS_POSIX_API RTEMS_SMP
*** TEST TOOLS: 10.3.1 20210409 (RTEMS 6, RSB ad54d1dd3cf8249d9d39deb1dd28b2f294df062d, Newlib eb03ac1)
TA1  - rtems_clock_get_tod - 09:00:00   12/31/1988
TA2  - rtems_clock_get_tod - 09:00:00   12/31/1988
TA3  - rtems_clock_get_tod - 09:00:00   12/31/1988
TA1  - rtems_clock_get_tod - 09:00:05   12/31/1988
TA2  - rtems_clock_get_tod - 09:00:10   12/31/1988
TA1  - rtems_clock_get_tod - 09:00:10   12/31/1988
TA1  - rtems_clock_get_tod - 09:00:15   12/31/1988
TA3  - rtems_clock_get_tod - 09:00:15   12/31/1988
TA2  - rtems_clock_get_tod - 09:00:20   12/31/1988
TA1  - rtems_clock_get_tod - 09:00:20   12/31/1988
TA1  - rtems_clock_get_tod - 09:00:25   12/31/1988
TA2  - rtems_clock_get_tod - 09:00:30   12/31/1988
TA1  - rtems_clock_get_tod - 09:00:30   12/31/1988
TA3  - rtems_clock_get_tod - 09:00:30   12/31/1988

*** END OF TEST CLOCK TICK ***

[ RTEMS shutdown ]

Follow up#

This is just one possible way to boot the RTEMS image. For a development environment you may wish to configure u-boot to boot the RTEMS image from a TFTP server. For a production environment, you may wish to download, configure, and build u-boot, or develop a BOOT.BIN image with the RTEMS application.

8.1.4.5. Clock Driver#

The clock driver uses the ARM Generic Timer.

8.1.4.6. Console Driver#

The console driver supports the default Qemu emulated ARM PL011 PrimeCell UART as well as the physical ARM PL011 PrimeCell UART in the ZynqMP hardware.

8.1.4.7. SDHCI Driver#

The ZynqMP bsp has an SDHCI driver which allows writing to and reading from SD cards. These can be tested in qemu using the “-sd” option. For example:

qemu-system-aarch64 -no-reboot -nographic -serial mon:stdio \
 -machine xlnx-zcu102 -m 4096 -kernel media01.exe -sd example.img

The SD card image should have an MSDOS partition table with a single partition containing a FAT file system.

8.1.4.8. Network Configuration#

When used with LibBSD, these BSP variants support networking via the four Cadence GEM instances present on all ZynqMP hardware variants. All interfaces are enabled by default, but only interfaces with operational MII busses will be recognized and usable in RTEMS. Most ZynqMP dev boards use RGMII with CGEM3.

When used with lwIP from the rtems-lwip integration repository, these BSP variants support networking via CGEM0 and one of the other CGEM* instances simultaneously. This is a limitation of the Xilinx driver, specifically in code referring directly to XPAR_XEMACPS_0_BASEADDR. Attempting to use more than two interfaces simultaneously may cause unexpected behavior. Attempting to use a set of two interfaces that does not include CGEM0 may cause unexpected behavior.

The interfaces will not come up by default under lwIP and must be configured manually. There are examples of this in the start_networking() implementation in netstart.c as used by the network tests.

8.1.4.9. Running Executables on QEMU#

Executables generated by these BSPs can be run using the following command:

qemu-system-aarch64 -no-reboot -nographic -serial mon:stdio \
 -machine xlnx-zcu102 -m 4096 -kernel example.exe