Loading...
 

SW4STM32 and SW4Linux fully supports the STM32MP1 asymmetric multicore Cortex/A7+M4 MPUs

   With System Workbench for Linux, Embedded Linux on the STM32MP1 family of MPUs from ST was never as simple to build and maintain, even for newcomers in the Linux world. And, if you install System Workbench for Linux in System Workbench for STM32 you can seamlessly develop and debug asymmetric applications running partly on Linux, partly on the Cortex-M4.
You can get more information from the ac6-tools website and download (registration required) various documents highlighting:

System Workbench for STM32

Forum List Topic List

You are viewing a reply to APSR (Application Processor Status Register)  

APSR (Application Processor Status Register)

Posted by Guy on 2019-02-21 10:55

Hi Ayoub,

The code runs each seconds and sometimes I get this behavior (once a day, once a week).
In the case of the breakpoint s14=50 s15=4.1366
vcmpe s15, s14 should set the flags based on s15-s14 which gives a negative value so the N flag=1
but the ble (branch if Less or Equal) does not jump confirmed by the APSR bits 28 to 31 = 0
so the vcmpe has not set the flag or the flag has disapeared for unknown reason that I try to understand

Best regards

Reads: 1944
Link
Posted by ayoub.bourjilat on 2019-02-21 12:01 France


First ,you can check the bit 31 in the FPSCR after the execution of the vmcpe (in the assembly view)
vmcpe set the flags in the FPSCR and after copy the values NZCV to APSR.

Second, you can use the Instruction Synchronization Barrier (ISB --> __ISB()) to flush the pipeline in the processor so that all instructions following the ISB are fetched from cache or memory after the instruction has completed. It ensures that the effects of context altering operations and any branches that appear in program order after it (the ISB) are always written into the branch prediction logic with the context that is visible after the ISB instruction (this will ensure correct execution of the instruction stream)

Best regards,
Ayoub
AC6

Link
Posted by Guy on 2019-02-21 14:31

Thanks Ayoub,

This is random and seldom, so 99.9999% the flags will be set correctly by the vmcpe.
All my code is C or C++.
the original code was
if (m_fCoor_I > 50.0F)
m_fCoor_I = 50.0F;
does it means I need to integrate the __ISB() instruction before each floating point comparaisons because I have many.

As a workaround I modified to have the comparison in integer
long int lCorr = m_fCorr_I;
if (lCorr > 50)
m_fCorr_I=50.0F;

Best regards

Link