BELK-AN-001: Asymmetric Multiprocessing (AMP) on Bora – Linux FreeRTOS

Info Box Applies to Bora Applies to BORA Xpress Applies to BORA Application Notes Applies to BORA Xpress Application Notes

This application note was validated against specific versions of the kit only. It may not work with other versions. Supported versions are listed in the History section.

History

Version	Date	BELK version	Notes
1.0.0	November 2013	1.1.0	First release
1.0.1	November 2013	1.1.0	Added UART0 pinout information Minor fixes
1.1.0	November 2013	1.1.0	Added support for RPMsg example
1.5.0	December 2013	1.1.0	Added chapter related to Lauterbach debugger
1.5.1	January 2014	1.1.0	Minor fixes
1.6.0	April 2014	2.0.0	Minor fixes Updated for BELK 2.0.0 release
2.0.0	September 2015	3.0.0	Migration to BELK 3.0.0 Added support for BoraX
2.0.1	July 2022	3.0.0	Added link for scripts download

Introduction

This application note describes how to build the software components required to set up asymmetric multi-processing (AMP for short) configuration required to run Linux OS on the first Cortex-A9 core (also denoted as core #0) and FreeRTOS on the second Cortex-A9 core (also denoted as core #1) of the Zynq SOC.

Asymmetric Multiprocessing (AMP) allows a multiprocessor/multicore system to run multiple Operating Systems (OS) that are independent of each other. In other words, each CPU has its own private memory space, which contains the OS and the applications that are to run on that CPU. In addition, there can be some shared memory space that is used for multiprocessor communication. This is contrasted with Symmetric Multiprocessing (SMP), in which one OS runs on multiple CPUs using a public shared memory space. Thanks to AMP, developers can use open-source Linux and FreeRTOS operating systems and the RPMsg Inter Processor Communication (IPC) framework between the Zynq's two high-performance ARM® Cortex™-A9 processors to quickly implement applications that need to deliver deterministic, real-time responsiveness for markets such as automotive, industrial and others with similar requirements. For further information, please refer to this link.

Two different examples are here provided. The first one – HelloWorld – shows basic functionalities while the second – RPMsg-based application – exploits more sophisticated techniques to handle inter-processors communication and synchronization. This latter configuration is based on RPMsg mechanism as described in Xilinx document UG978 (v2013.04, April 22, 2013).

A notable application where AMP configuration has been leveraged is described here.

PDF version of this Application Note can be downloaded here.

AMP on Bora

The following sections detail how to build the software components required to set up asymmetric multi-processing (AMP for short) configuration required to run Linux OS on first Cortex-A9 core and FreeRTOS on second Cortex-A9 core. The prerequisites are:

• Vivado® Design Suite version 2013.3 with Xilinx SDK (Webpack license is minimum requirements)
• Python 2.7.x (C:\Python27 must be the installation directory on Windows)
• TBD Bora Embedded Linux Kit version 2.0.0 (BELK for short). Please refer to BELK Quick Start Guide for further details.
• BORA FreeRTOS repository (please refer to section #Importing the FreeRTOS repository into the SDK).

Building the software components

Vivado project

• log into the development host
• Assuming that a local repository has not been created, clone the remote Bora git repository (the -b option is used to automatically checkout the current branch):

git clone git@git.dave.eu:dave/bora/bora.git -b bora

• Enter the git directory
• Switch to bora branch (not required if this is already the current branch):

git checkout bora

Set project directory variable:

export PROJ_DIR=$(pwd)/../bora-build-YYYYMMDD-nobk

Configure Vivado settings:

. /opt/Xilinx/Vivado/2013.3/settings64.sh

Launch Vivado with build_project script:

vivado -mode tcl -source build_project.tcl -notrace -tclargs "-bitstream"

FSBL

Once the Vivado project build is completed, the hardware configuration can be exported starting the SDK to build the FSBL. From the SDK GUI:

• Create a new application project, as shown in the picture below:

• Configure the application settings as shown in the pictures below:

• Click finish to launch FSBL build process
• Create the binary from the FSBL ELF chosing one of the following options:
  • manually launch the command: arm-xilinx-eabi-objcopy -v -O binary $PROJ_DIR/bora.sdk/SDK/SDK_Export/bora_FSBL/Debug/bora_FSBL.elf $PROJ_DIR/bora.sdk/SDK/SDK_Export/bora_FSBL/Debug/bora_FSBL.bin
  • configure the automatic binary generation on project build. In Project Explorer, right-click on bora_FSBL project and select C/C++ Build Settings and add the command arm-xilinx-eabi-objcopy -v -O binary ${ProjName}.elf ${ProjName}.bin on Post-build steps

N.B. When the Vivado project is modified, the binary must be re-generated with the following command:

python fpga-bit-to-bin.py --flip $PROJ_DIR/bora.runs/bora_run_impl/bora_design_wrapper.bit $PROJ_DIR/bora.runs/bora_run_impl/bora_design_wrapper.bin

FreeRTOS applications

The following sections describe the steps required to configure and build both the Helloworld and the RPMsg-based examples.

Importing the FreeRTOS repository into the SDK

• Assuming that a local repository has not been created, clone the remote freeRTOS git repository:

git clone git@git.dave.eu:dave/bora/freertos.git

• Enter the git directory
• Switch to freertos-AMP branch:

git checkout freertos-AMP

• In SDK gui import new repository: Xilinx Tools->Repositories

• Click New... to add a new repository under Local or Global Repositories, and select the freeRTOS repository directory:

• Click Rescan Repositories , Apply and OK
• At the end of the procedure, applications based on freeRTOS operating system can be built

Building Example #1: HelloWorld application

The first example shows basic AMP functionalities. On FreeRTOS side, UART0 is used to implement a simple console. This port is routed via EMIO signals to pin-strip connector of BoraEVB. Since these signals are driven by FPGA Bank #34, these pins are 3.3V. Thus a RS232 transceiver or an USB/UART bridge should be used in order to connect the console on a PC. The signals are routed to the JP17 connector of the BoraEVB as reported below:

• JP17.4 – UART0_TX
• JP17.6 – UART0_RX

Please follow the steps listed below to build a HelloWorld application that prints a message on UART0 (via EMIO) on FreeRTOS running on Bora core #1.

• From the SDK GUI, create e new application project:

• Configure the application settings as shown in the pictures and table below:

• • Project name: helloworld_freeRTOS
  • Hardware Platform: hw_platform_0
  • Processor: ps7_cortexa9_1
  • OS Plaftorm: freertos_zynq
  • Language: C
  • Board Support Package: Create New
  • Type: FreeRTOS Hello World AMP template
• Click finish to launch the application build process
• Create the binary from the application ELF chosing one of the following options:
  • manually launch the command: arm-xilinx-eabi-objcopy -v -O binary $PROJ_DIR/bora.sdk/SDK/SDK_Export/hellowordl_freeRTOS/Debug/hellowordl_freeRTOS.elf $PROJ_DIR/bora.sdk/SDK/SDK_Export/hellowordl_freeRTOS/Debug/hellowordl_freeRTOS.bin
  • configure the automatic binary generation on project build. In Project Explorer, right-click on helloworld_freeRTOS project and select C/C++ Build Settings and add the command arm-xilinx-eabi-objcopy -v -O binary ${ProjName}.elf ${ProjName}.bin on Post-build steps.

Building Example #2: RPMsg-based application

The procedure needed to build this application is similar to the one used to build HelloWorld application. The only difference is that the FreeRTOS Latency AMP template must be selected. In this case please note that:

• the standard Linux infrastructure will be used to load the firmware for the second core
• Linux will start in SMP mode, running on both cores; then CPU1 will be shutdown and FreeRTOS firmware will be loaded and run.

This example application exploits TTC1 timer to measure IRQ latencies as described in Xilinx UG978. In addition to that, GPIO0 (pin JP21.16 on BoraEVB) will be toggled every time ISR is invoked.

Once the build process is completed, the executable file in .elf format will be generated (we suggest to name it freertos). Creating the .bin file is not required.

• Project name: RPMsg_freeRTOS
• Hardware Platform: hw_platform_0
• Processor: ps7_cortexa9_1
• OS Plaftorm: freertos_zynq
• Language: C
• Board Support Package: Create New
• Type: FreeRTOS Latency AMP

To run this example, Linux kernel must be rebuilt too. First of all copy the freertos executable file in .elf format (freertos) into the directory firmware of Linux kernel tree. Then configure the kernel using bora_amp_defconfig as configuration file and enter the following command line, that changes the default load address of kernel and launches the building of both the kernel image and the modules:

bash# make UIMAGE_LOADADDR=0x10008000 uImage modules
[...]
  OBJCOPY arch/arm/boot/zImage
  Kernel: arch/arm/boot/zImage is ready
  UIMAGE  arch/arm/boot/uImage
Image Name:   Linux-3.9.0-bora-1.1.0-xilinx-00
Created:      Thu Nov 21 15:55:07 2013
Image Type:   ARM Linux Kernel Image (uncompressed)
Data Size:    3217192 Bytes = 3141.79 kB = 3.07 MB
Load Address: 10008000
Entry Point:  10008000
  Image arch/arm/boot/uImage is ready

The file arch/arm/boot/uImage is the binary image of the kernel that must be used to boot the system. The following kernel modules, resulting from the kernel build procedure, must be copied from the building directory to the root file system (usually into /lib/modules/<kernel version>/kernel, but any other directory can be used):

  LD [M]  drivers/remoteproc/remoteproc.ko
  LD [M]  drivers/remoteproc/zynq_remoteproc.ko
  LD [M]  drivers/rpmsg/rpmsg_freertos_statistic.ko
  LD [M]  drivers/rpmsg/virtio_rpmsg_bus.ko
  LD [M]  drivers/virtio/virtio.ko
  LD [M]  drivers/virtio/virtio_ring.ko
  LD [M]  net/rpmsg/rpmsg_proto.ko

For further details on kernel modules, please refer to this link.

Linux Device Tree

The Flattened Device Tree (FDT) is a data structure for describing the hardware in a system (for further information, please refer to http://elinux.org/Device_Tree). Both Example #1 and Example #2 requires some modifications to the standard Bora device tree (to initialiaze UART0 port and to properly initialize the RPMsg infrastructure, respectively). Please use the kernel branch bora, that already includes the aforementioned patches (for further details, please refer to the arch/arm/boot/dts/bora.dts file and commit descriptions on the Linux git repository). For detailed instructions on how to build the Linux kernel and the Device Tree, please refer to the BELK Quick Start Guide.

Running the demo applications

Example #1: HelloWorld application

This section describes how to run freeRTOS HelloWorld example application on BORA using AMP (Linux + FreeRTOS). Plese follow the steps listed below:

• Place all the binary files into the host tftp directory:
  • Kernel: uImage
  • Device Tree: bora.dtb
  • First stage bootloader: bora_FSBL.bin
  • FPGA bitstream: bora_design_wrapper.bin
  • FreeRTOS application: helloworld_freeRTOS.bin
• Start the Bora system
• From the U-Boot shell, update the FSBL with the following commands:

run load_fsbl
run update_fsbl

• Reset the board to reboot with the new FSBL
• Add the following U-Boot environment variables:

setenv addcons 'setenv bootargs ${bootargs} console=${console},115200n8 cma=16M debug maxcpus=${nr_cpus}'
setenv addmem 'setenv bootargs ${bootargs} mem=$(kernel_mem)'
setenv kernel_mem 1008M
setenv nr_cpus 1
setenv net_nfs 'run program_fpga; run load_freertos; run loadk nfsargs addip addcons addmem; bootm ${loadaddr_kern} - ${loadaddr_ftd}'
setenv load_freertos 'tftp ${freertos_addr} ${freertos_file};mw.l 0xFFFFFFF0 ${freertos_addr}'
setenv freertos_addr 0x3F000000
setenv freertos_file bora/BELK/helloworld_freeRTOS.bin
setenv fpga_file BELK/bora_design_wrapper.bin

• • this is a brief description of these variables

    • program_fpga: Loads FPGA binary from TFTP and programs the bitstream
    • load_freertos: Loads freertos application binary from TFTP and writes application start address for core #1
    • mem=${kernel_memory}: sets maximum kernel memory (1008M = 1024M - 16M)
    • maxcpus=${nr_cpus}: sets maximum Linux cores to 1

Last step consists of booting the system by running the following command:

run net_nfs

Example #2: RPMsg-based application

As stated before, this example shows a more sophisticated approach that allows for:

• using a standardized communication channel between the two cores (RPMsg)
• exploiting a standardized mechanism to load the firmware of second core.

This approach determines a different initialization process with respect to example #1. In this case the initialization sequence is:

1. linux kernel boots, enabling and using both cores
2. RPMsg and virtio drivers (compiled as modules) are loaded
3. core #1 is released
4. FreeRTOS binary image is loaded
5. core #1 is started.

In other words, boot process of core #1 is under the control of the Linux o.s. In principle this allows a dynamic use of the core #1 that can be allocated for FreeRTOS application only when it is actually needed.

The example performs IRQ latency measurements on FreeRTOS side by using a hardware timer. These measures are collected by the counterpart application running on Linux side and shown on console. Plese follow the steps listed below:

• Place all the binary files into the host tftp directory:
  • Linux kernel: uImage
  • Device Tree: bora.dtb
  • First stage bootloader: bora_FSBL.bin
  • FPGA bitstream: bora_design_wrapper.bin
  • FreeRTOS application: freertos
• Start the Bora system
• From the U-Boot shell, update the FSBL with the following commands:

run load_fsbl
run update_fsbl

• Reset the board to reboot with the new FSBL
• Add the following U-Boot environment variables (please note that, when using the RPMsg mechanism, it's not required to set the maxcpus=${nr_cpus} variable):

setenv addcons 'setenv bootargs ${bootargs} console=${console},115200n8 cma=16M debug'
setenv addmem 'setenv bootargs ${bootargs} mem=$(kernel_mem)'
setenv kernel_mem 496M
setenv net_nfs 'run program_fpga; run loadk nfsargs addip addcons addmem; bootm ${loadaddr_kern} - ${loadaddr_ftd}'
setenv freertos_addr 0x3F000000
setenv fpga_file BELK/bora_design_wrapper.bin

• • this a brief description of these variables

    • program_fpga: Loads FPGA binary from TFTP and programs the bitstream

      load_freertos: Loads freertos application binary from TFTP and writes application start address for core #1

• Boot the system running the following command: run net_nfs

When booting, the Linux kernel will print out the following message to indicate it has been relocated to address 0x10000000:

[    0.000000] Machine: Xilinx Zynq Platform, model: Bora
[    0.000000] Change memory bank to 10000000-2fffffff
[    0.000000] cma: CMA: reserved 16 MiB at 2f000000

To start the example, please enter the following commands on Linux side to load the required modules:

insmod  drivers/virtio/virtio.ko
insmod  drivers/virtio/virtio_ring.ko
insmod  drivers/rpmsg/virtio_rpmsg_bus.ko
insmod  net/rpmsg/rpmsg_proto.ko
insmod  drivers/remoteproc/remoteproc.ko
insmod  drivers/remoteproc/zynq_remoteproc.ko
insmod  drivers/rpmsg/rpmsg_freertos_statistic.ko

Linux kernel will print these messages, informing that the communication between the two cores has been established:

[   17.966158] NET: Registered protocol family 41
[   18.036698] CPU1: shutdown
[   18.045287]  remoteproc0: 0.remoteproc-test is available
[   18.050522]  remoteproc0: Note: remoteproc is still under development and considered experimental.
[   18.059554]  remoteproc0: THE BINARY FORMAT IS NOT YET FINALIZED, and backward compatibility isn't yet guaranteed.
[   18.077341]  remoteproc0: powering up 0.remoteproc-test
[   18.082668]  remoteproc0: Booting fw image freertos, size 2357682
[   18.103607]  remoteproc0: remote processor 0.remoteproc-test is now up
[   18.113339] virtio_rpmsg_bus virtio0: rpmsg host is online
[   18.118795]  remoteproc0: registered virtio0 (type 7)
[   18.124417] virtio_rpmsg_bus virtio0: creating channel rpmsg-timer-statistic addr 0x50
[   18.151586] rpmsg_freertos_statistic rpmsg0: new channel: 0x400 -> 0x50!

Then run the latencystat application as shown below. The typical output will look like this:

root@bora:~# ./latencystat -b
Linux FreeRTOS AMP Demo.
   0: Command 0 ACKed
   1: Command 1 ACKed
Waiting for samples...
   2: Command 2 ACKed
   3: Command 3 ACKed
   4: Command 4 ACKed
-----------------------------------------------------------
Histogram Bucket Values:
        Bucket 323 ns (36 ticks) had 38 frequency
        Bucket 341 ns (38 ticks) had 299 frequency
        Bucket 512 ns (57 ticks) had 1 frequency
        Bucket 746 ns (83 ticks) had 1 frequency
-----------------------------------------------------------
Histogram Data:
        min: 323 ns (36 ticks)
        avg: 332 ns (37 ticks)
        max: 746 ns (83 ticks)
        out of range: 0
        total samples: 339
-----------------------------------------------------------

This application is extremely useful for evaluating how CPU load on first core affects IRQ latency. In case latency does not satisfy real-time requirements, it may be necessary to adjust arbitration priorities of processor's interconnect subsystem. For further details, please refer to chapter Interconnect of Zynq Technical Reference Manual.

N.B. prior to launching the latencystat application, make sure that the governor is set to performance with the following command:

echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

Advanced debugging techniques for AMP Linux+FreeRTOS configuration

Introduction

When working with complex real-time configurations such as AMP Linux+FreeRTOS, debugging requirements increase dramatically. This chapter – written in collaboration with Lauterbach SRL – shows how these issues can be tackled with Lauterbach TRACE32 ® debugger (1). The following picture shows the BoraEVB connected to Lauterbach PowerDebug Interface/USB3 via J18 connector. By default, the board is configured to chain Xilinx PL TAP and ARM DAP (please refer to chapter JTAG and DAP Subsystem of Zynq Technical Reference Manual for more details).

BoraEVB connected to Lauterbach PowerDebug Interface/USB3

The following sections describe in detail how to configure TRACE32® debugger to support debug of Linux running on the first Zynq core, and FreeRTOS, running on the second Zynq core.

(1) The techniques described in this chapter apply to the Example #1: HelloWorld FreeRTOS application (please refer to section TBD).

Prerequisites

• LA-3500 Power Debug USB3 or LA-7705 Power Debug Ethernet or LA-7699 PowerDebug II
• LA-7843 JTAG Debugger for Cortex-A/-R
• LA-7960X License for Multicore Debugging
• TRACE32 PowerView for ARM (Release: Feb 2013, Software Version: R.2013.02.000045901)
• Optional: LA-7970X Trace License for ARM (Debug Cable)

For a general introduction to debug features provided by TRACE32 tools, please refer to:

• Debugger Basics – Training manual (training_debugger.pdf)
• Training HLL Debugging manual (training_hll.pdf)

TRACE32 configuration

In AMP configuration, each core runs a unique code, already fixed at compile time. The CPU interoperates with other processing units, exchanging data through dedicated channels (for example, shared memory buffers or peripheral units). Lauterbach supports these architectures with different TRACE32 instances, each one connected to a single core, in core view configuration where debug focus is on single processor. However, as the cores do not work independently but perform the application task together and in parallel, it is possible to start and stop all the cores simultaneously. This is the only way to test the interaction between the cores and to monitor and control the entire application. Moreover, as each core run a separate part of the application, the majority of the symbol and debug information is assigned exclusively to the corresponding core.

In the following paragraphs, the basic TRACE32 multicore configuration for a single device will be introduced. For more details, please refer to ICD Debugger User's Guide (debugger_user.pdf).

Multicore configuration

For the configuration of TRACE32 application, reference scripts are provided from Lauterbach. The first GUI must be started manually and must register itself to share a common JTAG handler with other TRACE32 applications. This is done setting the option CORE= in the configuration file (default file name: config.t32).

PBI=		; within config file of first core
USB
CORE=1

or:

PBI=		; within config file of first core
NET
NODE=<IP_address>
PACKLEN=1024
CORE=1

Nevertheless, the setting to define which core is addressed, actually is done later on.

Multicore synchronization

To use the start/stop synchronization between different core debuggers, the INTERCOM port settings are necessary. This is done assigning predefined port numbers in the configuration file to each TRACE32 application (option PORT=).

IC=NETASSIST		; within config file of first core
PORT=20001

IC=NETASSIST		; within config file of second core
PORT=20002

Startup scripts

In order to use a generic configuration file for each TRACE32 instance, there is the possibility to use just one generic template file for all cores. The particular settings are passed as parameter. This is shown in the reference script:

amp_start_core0.bat

which refers to the configuration file:

amp_config.t32

The batch file starts automatically this startup script:

amp_demo.cmm

After booting the first TRACE32 GUI, the second GUI will be started automatically by the startup script. See the reference script:

amp_demo_start_core1.cmm

For more details about PRACTICE batch language, please refer to:

• Training PRACTICE manual (training_practice.pdf)
• PRACTICE Script Language User´s Guide (practice_user.pdf)
• PRACTICE Script Language Reference Guide (practice_ref.pdf)

For your convenience, please find a zip file containing the Lauterbach scripts here.

PRACTICE macros for multiple TRACE32

The startup script, started automatically at the first TRACE32 application, is fully able to configure the whole debug system, providing PRACTICE commands both to the current instance of TRACE32 application, and to the second instance. It’s also possible to deliver the same PRACTICE command to both instances with a single command line. The command redirection is possible using the INTERCOM feature. Typically some PRACTICE macros can be defined for this purpose.

&core0=""                         ;only to improve readability
&core1="intercom localhost:&intercomport_core1"
&both="GOSUB intercom_both "
where:
intercom_both:
  LOCAL &param
  ENTRY %Line &param
  &core0 &param
  &core1 &param
RETURN

In this way, all CPU-specific configuration commands can be performed in the same way for each TRACE32 application, or distinguishing between different configurations. For example:

&both SYStem.RESet

or:

&core0 SYStem.CPU ZYNQ-7000CORE0
&core1 SYStem.CPU ZYNQ-7000CORE1

The SYnch command

The synchronization between different TRACE32 applications is done by SYnch command group, which allows the following purposes:

• to establish a start/stop synchronization between the cores controlled by different TRACE32 instances;
• to allow concurrent assembler single steps between the cores controlled by different TRACE32 instances;
• to allow synchronous system mode changes between the cores controlled by different TRACE32 instances.

The SYnch settings are reported below:

• Connect
  • Establish a connection to the debugger attached to the defined communication port(s). Several debuggers ports can be specified, separated by space.
• MasterGo ON
  • If the program execution is started, the program execution for all other processors which have SlaveGo ON is also started.
• MasterBrk ON
  • If the program execution is stopped, the program execution for all other debuggers which have SlaveBrk ON is also stopped.
• MasterStep ON
  • If an asm single step is executed, all processors which have SlaveStep ON will also asm single step.
• MasterSystemMode ON
  • Invite other TRACE32 instances to perform system mode changes synchronously. System mode changes are typically performed by the commands SYStem.Mode <mode>
• SlaveGo ON
  • The program execution is started, if a processor with MasterGo ON starts its program execution.
• SlaveBrk ON
  • The program execution is stopped, if a processor with MasterBrk ON stops its program execution.
• SlaveStep ON
  • A asm single step is performed, if a processor with MasterStep On performs an asm single step.
• SlaveSystemMode ON
  • Synchronize with system mode changes in connected TRACE32 instances.

A summary of SYnch configuration is provided with command TargetSystem, which also allows to easily and rapidly modify the SYnch mode options. Moreover the TargetSystem command provides a general overview of the whole multicore configuration and of the current state.

TargetSystem DEFault Title SYnch.All InterComPort /Global

There is a time delay between reaction of different cores. The reaction time of the slave core depends on the technical realisation of the synchronization. If no specific configuration is performed, the synchronization is done by software (eg: the master debugger informs the slave debugger via socket communication on the host about specified events). On the other side, if the on-chip Cross Trigger Interface is configured, the synchronization takes place directly on the processor. This is a faster solution and the time delay between reaction of different cores becomes around 0-10ns. The CTI interface for chip Zynq is configured with the following commands. If CTI is configured, TRACE32 will use the faster solution for the synchronization.

&core0 SYStem.CONFIG.CTI.Base 0x80098000
&core0 SYStem.CONFIG.CTI.Config CORTEXV1

&core1 SYStem.CONFIG.CTI.Base 0x80099000
&core1 SYStem.CONFIG.CTI.Config CORTEXV1

Setting up the Linux debug configuration

The symbolic information is useful for HLL debugging, or setting breakpoints, stepping through the code, viewing variables, and many other aspects of debugging. The compiler must be configured in order to generate debug symbols. The vmlinux file for the running kernel must be available, in order to load the kernel debug symbols. No instrumentation is needed in the kernel source code for debugging with Lauterbach, but it's important that the vmlinux file is generated from the same kernel build as the zImage or uImage running on the system. The Data.LOAD command is used to load the kernel symbols, and the sYmbol.SourcePATH command can be used, if necessary, to define additional search directories for the source files. The Data.LOAD command for vmlinux is applied to &core0, so that symbol information is not shared with the other TRACE32 application.

Specific options must be configured to avoid automatic Break of TRACE32 debugger, in case any of the following events happens due to normal Linux operations.

TrOnchip.Set UNDEF OFF    ; may be used by Linux for FPU detection
TrOnchip.Set DABORT OFF   ; used by Linux for page miss!
TrOnchip.Set PABORT OFF   ; used by Linux for page miss!

In the following paragraphs, the basic TRACE32 Linux configuration will be introduced. For more details, please refer to:

• Training Linux Debugging manual (training_rtos_linux.pdf)
• RTOS Debugger for Linux - Stop Mode manual (rtos_linux_stop.pdf).

Kernel awareness

TRACE32 kernel awareness technology makes debugger aware of the OS running in the target system. Debug is significantly simplified, as the user can immediately access all the components of the OS and the application. The Executable and Linkable Format (ELF) binaries, created at kernel build time, are used also by Linux awareness. The Linux kernel awareness is configured with the commands:

; loads Linux awareness
&core0 TASK.CONFIG ~~/demo/arm/kernel/linux/linux-3.x/linux3.t32
; loads Linux menu
&core0 MENU.ReProgram ~~/demo/arm/kernel/linux/linux-3.x/linux.men

The Linux kernel awareness is loaded into the first TRACE32 application, and will not affect the second one. The Linux menu file (linux.men) includes many useful menu items developed for the TRACE32 GUI to ease Linux debugging.

MMU support

In Linux embedded, the Lauterbach debuggers provide a very tight integration with the RTOS. The kernel awareness supports Linux MMU format and is able to handle virtual memory addressing.

MMU.FORMAT LINUX swapper_pg_dir 0xc0000000--0xc1ffffff 0x00000000
TRANSlation.Create 0xc0000000--0xc1ffffff 0x00000000
TRANSlation.COMMON 0xbf000000--0xffffffff
TRANSlation.TableWalk ON
TRANSlation.ON

where the virtual address range is the virtual-to-physical kernel address mapping, according with results of command MMU.List KernelPageTable, executed when the kernel is up and running. In the command TRANSlation.COMMON, the virtual address range has been extended below the kernel start address, because kernel objects are loaded in this memory range.

Debugging of kernel modules

The Linux kernel can be compiled to allow linking of additional modules at runtime (kernel objects). The Lauterbach debuggers also support kernel modules debugging, starting from the initialization function.

Debugging of user processes, threads, shared objects

User process debugging is also available, starting from the very beginning of the process. If the process loads shared objects, they are loaded in the process address space when the related instructions are executed for the first time (demand paging). The Lauterbach debuggers also support debug of threads for multithreaded processes. In this case, the same address space is shared between different threads and the symbolic information can be loaded only once per process. In general, the same techniques used for debugging kernel code, such as setting breakpoints, stepping through code, watching variables, and viewing memory contents, can be performed in the same way for processes and tasks. Virtual address spaces are distinguished in TRACE32 using the concept of spaceID, which is enabled with the option:

SYStem.Option MMUspaces ON

The memory addressing is extended using the lower 16 bit of the process PID, allowing in this way to distinguish between equal virtual addresses for different processes.

Setting up the FreeRTOS debug configuration

A similar kernel awareness concept as Linux, is provided by Lauterbach for many other RTOS. Among the others, also FreeRTOS is supported with the following awareness configuration.

; load FreeRTOS awareness
&core1 TASK.CONFIG ~~/demo/arm/kernel/freertos/freertos.t32
; load FreeRTOS menu
&core1 MENU.ReProgram
~~/demo/arm/kernel/freertos/freertos.men

The FreeRTOS kernel awareness is loaded into the second TRACE32 application, and will not affect the first one. As of symbol information it’s enough to load the proper symbol file, redirecting the Data.LOAD command to &core1. In this way, the second TRACE32 application will have visibility of FreeRTOS HLL debug info. The FreeRTOS menu file (freertos.men) includes useful menu items developed for the TRACE32 GUI to ease FreeRTOS debugging.

For more details, please refer to RTOS debugger for FreeRTOS manual (rtos_freertos.pdf).

Onchip trace

The Zynq chip implements the ETB (Embedded Trace Buffer), a CoreSight hardware component providing on-chip trace functionality. The ETB stores program-flow trace information on-chip at high rates and at 32-bit data width. The data can be read out via JTAG, when the trace recording has ended. This trace method is enabled in TRACE32 with the following commands, respectively performed on each GUIs of AMP configuration:

Trace.METHOD Onchip    ; select the ETB as source                 ; for the trace information

The TRACE32 menu item Trace ? Configuration allows a full control of configuration, initialization and listing of trace information. The trace, recorded for each core by each AMP TRACE32 GUI, can be synchronized using the XTRACK feature of TRACE32. In this way, an easy comparison is possible of program flow of each core at the same time. The XTRACK feature is enabled with the following commands:

&core0 Synch.XTRACK localhost:&intercomport_core1
&core1 Synch.XTRACK localhost:&intercomport_core0

Each trace window will follow the time / record synchronization of other trace windows, if the option /Track is used. The following images show Linux onchip trace XTRACKED vs FreeRTOS onchip trace:

For further details, please refer to Training Real-time Trace manual (training_trace.pdf).

Summary view

In the pictures below, all the concepts previously discussed are shown as a summary global view of TRACE32 debugger, respectively for Zynq core 0 running a Linux kernel, and Zynq core 1 running a FreeRTOS based application.

Linux at Zynq core 0

FreeRTOS at Zynq core 1

Lauterbach References

This chapter has been written by Lauterbach italian branch office.

Contact information:

Lauterbach SRL

Via Enzo Ferrieri 12

20153 Milan (Italy)

Tel. +39 02 45490282

Email info_it@lauterbach.it

Web www.lauterbach.it

Related documents and additional resources

Document	Location
DAVE Embedded Systems Developers Wiki	http://wiki.dave.eu/index.php/Main_Page
Zynq-7000 Technical Reference Manual	http://www.xilinx.com/support/documentation/user_guides/ug585-Zynq-7000-TRM.pdf
Bora main page on DAVE Embedded Systems Developers Wiki	http://wiki.dave.eu/index.php/Category:Bora
Bora Hardware Manual	BORA HM
BoraEVB page on DAVE Embedded Systems Developers Wiki	http://wiki.dave.eu/index.php/BoraEVB
Vivado Design Suite User Guide: Embedded Processor Hardware Design	http://www.xilinx.com/support/documentation/sw_manuals/xilinx2013_2/ug898-vivado-embedded-design.pdf
Zynq-7000 All Programmable SoC: Concepts, Tools, and Techniques (CTT)	http://www.xilinx.com/support/documentation/sw_manuals/xilinx14_6/ug873-zynq-ctt.pdf
Zynq-7000 All Programmable SoC Software Developers Guide	http://www.xilinx.com/support/documentation/user_guides/ug821-zynq-7000-swdev.pdf
BELK Quick Start Guide	Provided with BELK
Xilinx UG978 (v2013.04) April 22, 2013	http://www.xilinx.com/support/documentation/sw_manuals/petalinux2013_04/ug978-petalinux-zynq-amp.pdf
Multi-OS Support (AMP & Hypervisor)	http://www.wiki.xilinx.com/Multi-OS+Support+%28AMP+%26+Hypervisor%29
Xilinx UG978	http://www.xilinx.com/support/documentation/sw_manuals/petalinux2013_04/ug978-petalinux-zynq-amp.pdf
Unsupervised AMP	https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/18842203/Unsupervised+AMP

Appendixes

U-Boot environment

The following is the U-Boot environment that can be printed using the print command (please note these are examples and that the actual variables may differ for different U-Boot settings), for both the FreeRTOS applications described in this application note.

Example #1: HelloWorld application

addcons=setenv bootargs ${bootargs} console=${console},115200n8 cma=16M debug maxcpus=${nr_cpus} 
addip=setenv bootargs ${bootargs} ip=${ipaddr}:${serverip}:${gateway}:${netmask}:${hostname}:${ethdev} 
addmem=setenv bootargs ${bootargs} mem=1008M 
baudrate=115200 
bootdelay=3 
bootfile=bora/uImage 
console=ttyPS0 
dt_base=0x005C0000 
ethact=Gem.e000b000 
ethaddr=00:0a:35:00:01:22 
ethdev=eth0 
fdt_high=0x1F000000 
fileaddr=0 
filesize=2f0ed0 
fpga_base=0x00180000 
fpga_file=belk/free_rtos/bora_design_wrapper.bin 
freertos_addr=0x3F000000 
freertos_file=bora/belk/free_rtos/helloworld_freertos.bin 
fsbl_base=0x40000 
ftd_file=bora/bora.dtb 
gateway=192.168.0.254 
header_base=0 
hostname=bora 
ipaddr=192.168.0.209 
jtagboot=echo TFTPing Linux to RAM...;tftp 0x8000 zImage;tftp 0x1000000 devicetree.dtb;tftp 0x800000 ramdisk8M.image.gz;go 0x8000 
kernel_size=0x140000 
load=tftp ${loadaddr} bora/u-boot.bin 
load_dt=tftp ${loadaddr} bora/bora.dtb 
load_fpga=tftp ${loadaddr} bora/${fpga_file} 
load_freertos=tftp ${freertos_addr} ${freertos_file};mw.l 0xFFFFFFF0 ${freertos_addr} 
load_fsbl=tftp ${loadaddr} bora/belk/free_rtos/bora_FSBL.bin 
load_h=tftp ${loadaddr} bora/boot_header-1.1.0 
loadaddr=0x08000000 
loadaddr_ftd=0x01000000 
loadaddr_kern=0x0 
loadk=tftp ${loadaddr_kern} ${bootfile};tftp ${loadaddr_ftd} ${ftd_file} 
modeboot=qspiboot 
net_nfs=run program_fpga; run load_freertos; run loadk nfsargs addip addcons addmem; bootm ${loadaddr_kern} - ${loadaddr_ftd} 
netmask=255.255.255.0 
nfsargs=setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath} 
nr_cpus=1 
program_fpga=run load_fpga;fpga load 0 ${loadaddr} 0x${filesize} 
qspiboot=sf probe 0 0 0;sf read 0x8000 0x100000 0x2c0000;sf read 0x1000000 0x3c0000 0x40000;sf read 0x800000 0x400000 0x800000;go 0x8000 
ramdisk_size=0x200000 
rootpath=/home/shared/devel/dave/bora-DBRx/sw/linux/rfs/BELK/ubuntu_12.04 
sdboot=echo Copying Linux from SD to RAM...;mmcinfo;fatload mmc 0 0x8000 zImage;fatload mmc 0 0x1000000 devicetree.dtb;fatload mmc 0 0x800000 ramdisk8M.image.gz;go 0x8000 
serverip=192.168.0.23 
stderr=serial 
stdin=serial 
stdout=serial 
u-boot_base=0x80000 
update=sf probe 0 0 0;sf erase ${u-boot_base} 0x80000;sf write ${loadaddr} ${u-boot_base} 0x80000 
update_dt=sf probe 0 0 0;sf erase ${dt_base} 0x40000;sf write ${loadaddr} ${dt_base} 0x40000 
update_fpga=sf probe 0 0 0;sf erase ${fpga_base} 0x440000;sf write ${loadaddr} ${fpga_base} 0x440000 
update_fsbl=sf probe 0 0 0;sf erase ${fsbl_base} 0x40000;sf write ${loadaddr} ${fsbl_base} 0x40000 
update_fsbl_nand=run load_fsbl; nand erase 0x40000 0x40000; nand write ${loadaddr} 0x40000 0x40000 
update_h=sf probe 0 0 0;sf erase ${header_base} 0x40000;sf write ${loadaddr} ${header_base} 0x40000

Example #2: RPMsg-based application

addcons=setenv bootargs ${bootargs} console=${console},115200n8 cma=16M debug 
addip=setenv bootargs ${bootargs} ip=${ipaddr}:${serverip}:${gateway}:${netmask}:${hostname}:${ethdev} 
addmem=setenv bootargs ${bootargs} mem=496M 
baudrate=115200 
bootdelay=3 
bootfile=bora/uImage 
console=ttyPS0 
dt_base=0x005C0000 
ethact=Gem.e000b000 
ethaddr=00:0a:35:00:01:22 
ethdev=eth0 
fdt_high=0x1F000000 
fileaddr=0 
filesize=2f0ed0 
fpga_base=0x00180000 
fpga_file=belk/free_rtos/bora_design_wrapper.bin 
freertos_addr=0x3F000000 
freertos_file=bora/belk/free_rtos/helloworld_freertos.bin 
fsbl_base=0x40000 
ftd_file=bora/bora.dtb 
gateway=192.168.0.254 
header_base=0 
hostname=bora 
ipaddr=192.168.0.209 
jtagboot=echo TFTPing Linux to RAM...;tftp 0x8000 zImage;tftp 0x1000000 devicetree.dtb;tftp 0x800000 ramdisk8M.image.gz;go 0x8000 
kernel_size=0x140000 
load=tftp ${loadaddr} bora/u-boot.bin 
load_dt=tftp ${loadaddr} bora/bora.dtb 
load_fpga=tftp ${loadaddr} bora/${fpga_file} 
load_freertos=tftp ${freertos_addr} ${freertos_file};mw.l 0xFFFFFFF0 ${freertos_addr} 
load_fsbl=tftp ${loadaddr} bora/belk/free_rtos/bora_FSBL.bin 
load_h=tftp ${loadaddr} bora/boot_header-1.1.0 
loadaddr=0x08000000 
loadaddr_ftd=0x01000000 
loadaddr_kern=0x0 
loadk=tftp ${loadaddr_kern} ${bootfile};tftp ${loadaddr_ftd} ${ftd_file} 
modeboot=qspiboot 
net_nfs=run program_fpga; run loadk nfsargs addip addcons addmem; bootm ${loadaddr_kern} - ${loadaddr_ftd} 
netmask=255.255.255.0 
nfsargs=setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath} 
nr_cpus=1 
program_fpga=run load_fpga;fpga load 0 ${loadaddr} 0x${filesize} 
qspiboot=sf probe 0 0 0;sf read 0x8000 0x100000 0x2c0000;sf read 0x1000000 0x3c0000 0x40000;sf read 0x800000 0x400000 0x800000;go 0x8000 
ramdisk_size=0x200000 
rootpath=/home/shared/devel/dave/bora-DBRx/sw/linux/rfs/BELK/ubuntu_12.04 
sdboot=echo Copying Linux from SD to RAM...;mmcinfo;fatload mmc 0 0x8000 zImage;fatload mmc 0 0x1000000 devicetree.dtb;fatload mmc 0 0x800000 ramdisk8M.image.gz;go 0x8000 
serverip=192.168.0.23 
stderr=serial 
stdin=serial 
stdout=serial 
u-boot_base=0x80000 
update=sf probe 0 0 0;sf erase ${u-boot_base} 0x80000;sf write ${loadaddr} ${u-boot_base} 0x80000 
update_dt=sf probe 0 0 0;sf erase ${dt_base} 0x40000;sf write ${loadaddr} ${dt_base} 0x40000 
update_fpga=sf probe 0 0 0;sf erase ${fpga_base} 0x440000;sf write ${loadaddr} ${fpga_base} 0x440000 
update_fsbl=sf probe 0 0 0;sf erase ${fsbl_base} 0x40000;sf write ${loadaddr} ${fsbl_base} 0x40000 
update_fsbl_nand=run load_fsbl; nand erase 0x40000 0x40000; nand write ${loadaddr} 0x40000 0x40000 
update_h=sf probe 0 0 0;sf erase ${header_base} 0x40000;sf write ${loadaddr} ${header_base} 0x40000

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