Gsg-linux-vt 01

Cross-Compiler toolchain

Baremetal compiler toolchain : nios2-elf-xxxxxxx

The baremetal compiler toolchain is built with “NewLib” and is for producing small target footprint application software, e.g. OS independent software applications and RTOS.

GCC switch - CFLAGS

• 
  https://sourcery.mentor.com/GNUToolchain/release2498
  

-mhal

-msys-lib=xxxxx

General:

-g (provides the default set of debug symbols)

-O2 (normal optimization)

-MP

Warning level:

-Wall

LINUX Development Environment

Cross-Compiler toolchain

Baremetal compiler toolchain : arm-none-eabi-xxxxxxx

Standard compiler toolchain : arm-linux-gnueabihf-xxxxxxx

The baremetal compiler toolchain is built with “NewLib” and is for producing small target footprint application software, e.g. OS independent software applications and RTOS.

The standard compiler toolchain is built with GNU “GLIBC” and is for producing application software for LINUX.

GCC switch - CFLAGS

• 
  http://gcc.gnu.org/onlinedocs/gcc-4.7.3/gcc
  

-mfloat-abi=softfp

-march=armv7-a

-mtune=cortex-a9

-mcpu=cortex-a9

-mfpu=vfpv3-d16

General:

-g (provides the default set of debug symbols)

-O2 (normal optimization)

–std=c99 or gnu99 (gnu99 is GNU dialect of ISO C99)

Warning level:

-Werror

Note: For cross-compiling involving HWLIB or SOCAL it is advisable to use “-std=gnu99” instead of “-std=c99” to solve some possible linking compatibility issue related to other GNU libraries.

64-Bit Host Development Machine Consideration

By default A 64-bit host machine can execute any 32-bit software applications without any problem but not the other way round. The only dependency a 64-bit host machine needed is the IA32 runtime libraries to be available.

If a user wants to use A 32-bit cross-compiler toolchains on a 64-bit Linux native host development machine, he needs to make sure those IA32 runtime libraries to be available on the 64-bit host development machine.

Below is the an example on how to install IA32 runtime libraries on Ubuntu 12.04.2 LTS

~$ sudo apt-get install libgl1-mesa-dri:i386

~$ sudo apt-get install ia32-libs-multiarch:i386

~$ sudo apt-get install ia32-libs

Generic “Makefile” Construction

Usually NIOS uC/OS II “Makefile” is generated automatically through Eclipse GUI, the content of the “Makefile” is standard except the “C_ARCH_FLAGS” which is processor architecture dependent.

Figure shows the generic “Makefile” example for building application software for ARM Cortex–A9 under LINUX environment. User need to be aware that “CROSS_COMPILER”, COMPILER_DIR” and “ARM_SCM_DIR” are location/tool specific and need to change accordingly.

Figure : Makefile

Using HWLIB and SOCAL

When porting application software form NIOS uC/OS II to ARM Cortex-A9 LINUX user are advisable to utilize Altera Hardware Library (HWLIB) and Altera SoC Abstraction Layer (SOCAL) as much as possible for hardware specific I/O access such as peripherals I/O, generic I/O, processor I/O etc. As both the HWLIB and SOCAL are conformed to C99 standard, the codes should compile without any problem with either Baremetal GCC cross-compiler toolchain or standard LINUX GCC cross-compiler toolchain.

Figure and Figure : code snippets illustrate the usage of generic I/O register read/write utilizing Altera SoC Abstraction Layer (SOCAL) .

Figure : Inclusion of Altera SoC Abstraction Layer (SOCAL) API header file

Figure : Memory read/write using Altera SoC Abstraction Layer (SOCAL) API

One important reminder to note here, if the porting code make use of POSIX API call, e.g. clock_gettime(…) than there are no choice but to use standard LINUX GCC cross-compiler toolchain as it is built with GNU “GLIBC”.

General Consideration of Porting From uC/OS II to LINUX

Porting from uC/OS II to LINUX is highly depended on the application or usage specific design. Generally porting from uC/OS II to LINUX will be easier as the later OS provided more complete support on scheduling mechanism, MMU, POSIX API and various GNU libraries.

uC/OS II Scheduling vs. LINUX Scheduling

uC/OS II is a preemptive real-time multitasking kernel in which the kernel is ready for operation at all times for the highest priority tasks. In the contrary, LINUX is using traditional periodic clock timer interrupt to achieve regular intervals to suspend a process. Due to uC/OS-II and LINUX are not comparable, mimic porting of uC/OS-II scheduling, timing, synchronization and inter-process communication mechanism are not encouraged. But for further reference on this topic, please refer to uC/OS-II - Port for the LINUX Operating System by Werner.Zimmermann.

Figure : Simple example of uC/OS II codeillustrated a simple example of uC/OS II codes and we need to consider application specific codes reside inside “task1” and “task2” and port them properly to ARM Cortex-A9 LINUX. The rest of the codes are uC/OS II architecture specific that not the interest of this porting guide.

Figure : Simple example of uC/OS II code

Memory Management Unit

uC/OS II does not had MMU management memory, thus the memory access is direct, e.g. all access is direct to the actual physical address and if a multi-process data protection is not implemented, this will easily lead to a system crash. Porting from NIOS uC/OS II to ARM Cortex-A9 LINUX is simpler as all the complexity of MMU management implementation is taken care by LINUX OS already. At a bare minimum all the custom codes related memory management from NIOS uC/OS II are advisable to remove accordingly when porting to ARM Cortex-A9 Linux.

Miscellaneous Porting Consideration

In summary, to port from NIOS uC/OS II to ARM Cortex-A9 LINUX is much simpler vs. the other way round. This is because the ARM Cortex-A9 architecture, timer interrupt, stack growth and process switching are well supported by LINUX OS architecture. Though the porting in this direction are simple, there are some miscellaneous definition that need to be aware, e.g. Figure : os_cpu.hFigure , data types from NIOS uC/OS II processor range must re-define properly for ARM Cortex-A9 LINUX target, Figure : stdint.h.

Figure : os_cpu.h

Figure : stdint.h

© 2013 Altera Corporation

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