FreeRtos, native Floats and Task switching

Kernel
1

cdebrebisson wrote on Monday, April 24, 2017:

Hello,

I am working with an ARM Cortex A7 running FreeRTOS and I am having a problem.
I have 2 tasks, running in parallel, computing different parts of mandelbrot set.
It does not work -:frowning:
Note that running only one of the 2 tasks works perfectly!

However, if I change the code for my task so that it uses ints (with 12 bit fixed point arithmetics), then there is no issues and I can do both calculations in parallelā€¦

It feels that FreeRTOS does not task switch the FPU registers. Is this assumption correct?
If yes, what other registers are not switched (NEON, ā€¦)

Regards,
Cyrille

2

rtel wrote on Monday, April 24, 2017:

See the section ā€œusing the floating point unitā€ on the following page:
http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html

Exactly what you need to do depends on the compiler you are using and
the version of FreeRTOS you are using.

3

glenenglish wrote on Monday, April 24, 2017:

I canā€™t find
configUSE_TASK_FPU_SUPPORT
anywhere in any source filesā€¦ using 9.0ā€¦
?

4

rtel wrote on Monday, April 24, 2017:

There are a few different Cortex-A ports, some with GIC support some
with proprietary interrupt controller support, and for different
compilers. configUSE_TASK_FPU_SUPPORT is in this version:
\FreeRTOS\Source\portable\GCC\ARM_CA9

5

glenenglish wrote on Tuesday, April 25, 2017:

ta. thatā€™s why I am not seeing it, itā€™s in one of the ports. very good. thanks.

6

cdebrebisson wrote on Tuesday, April 25, 2017:

Hello,

Thanks for your help, I did discover the configUSE_TASK_FPU_SUPPORT define and the vPortTaskUsesFPU(); function call.

It does work now!

Thanks!

Cyrille