ARM Cortex-A9 Intall Interrupt Handler bug?

2013-01-28
2013-09-16
  • John Wilkes
    John Wilkes
    2013-01-28

    The vPortInstallInterruptHandler() function in the ARM_Cortex-A9 port.c file has the following:

    unsigned long ulBank16 = 4 * ( ulVector / 16 );

    /* Is it Edge Triggered?. */
    if ( 0 != ucEdgeTriggered )
    {
    portGIC_SET( (portGIC_ICDICR_BASE(puxGICDistributorAddress + ulBank16) ),
         ( portGIC_READ(puxGICDistributorAddress + ulBank16) | ( 0x02 << ( ulOffset16 * 2 ) ) ) );
    }

    I think it wants to set the edge-triggered bit in the appropriate Interrupt Interrupt Configuration Register, but it looks like it is OR'ing the edge-triggered bit with the contents of the Interrupt Controller Type Register at GCDistributorAddress+4 (e.g. for "vector" 29).

    This makes no sense to me. Am I missing something? Why does it read (puxGICDistributorAddress + ulBank16) and OR the edge-triggered bit into that value?

    Seems like it should be something like this:

        portGIC_SET( (portGIC_ICDICR_BASE(puxGICDistributorAddress + ulBank16) ), ( ( 0x02 << ( ulOffset16 * 2 ) ) ) );

    -jw-

     
  • Richard
    Richard
    2013-01-28

    There is not (yet) an official Real Time Engineers ltd maintained Cortex-A9 port.  Did you get your code from the FreeRTOS Interactive site?  If so, please let me know which post the code came from and I may be able to ping the authour for a reply.

    Regards.

     
  • John Wilkes
    John Wilkes
    2013-01-28

    I hadn't seen that version, but it has the same edge-triggered code in vPortInstallInterruptHandler().

     
  • John Wilkes
    John Wilkes
    2013-01-29

    I have convinced myself that this is a bug in the code, but I don't think it matters for the Cortex-A9 MPCore, as ICDICR0 and ICDICR1 are read-only registers. Different implementations, e.g. single Cortex-A9 with a GIC, might have a problem.

    -jw-

     
  • Richard
    Richard
    2013-01-30

    Thanks for taking the time to mention this.  I will let the authors know.

    Regards.