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enable_irq()/disable_irq() in ARMCC V4

Hi everyone,

I have posted to this forum a couple months ago about using the enable_irq()/disable_irq() instruction intrinsics in RealView Compiler (ARMCC V4.0.0.728). In that occasion, I set up two software interrupts for calling such intrinsics, as they only have the intended effect when not in User Mode.

Just now, though, I realized that interrupts were not being disabled. I know for a fact that my SWI are set up appropriately, because they change the value of a flag I set up. Does anyone have any clue what could be happening? Documentation seems to be pretty clear about the fact that one enters supervisor mode during SWI, and that would be appropriate for enabling/disabling interrupts, but I must be missing something.

Relevant source code

void __SWI_8 (void)
{
  __enable_irq();
  __enable_fiq();
  interrupts_enabled = 1;
}

void __SWI_9 (void)
{
  __disable_irq();
  __disable_fiq();
  interrupts_enabled = 0;
}

Relevant links

Instruction Intrinsics
http://www.keil.com/support/man/docs/armcc/armcc_chdfgfab.htm

disable_irq()
www.keil.com/.../armccref_CJAFBCBB.htm

enable_irq()
www.keil.com/.../armccref_CJAEAEHA.htm

ARMCC: MODIFY IRQ FLAG TO ENABLE/DISABLE INTERRUPTS (RealView Compiler V3)
http://www.keil.com/support/docs/3229.htm

Thanks in advance,
--
George Andrew Brindeiro
Robotron Automation and Technology

Parents

0 George Brindeiro over 12 years ago

I tried doing the following:

void __SWI_8 (void)
{
  //__enable_irq();
  //__enable_fiq();
  int temp;

   __asm
  {
     MRS     temp, SPSR_cxsf        // Get SPSR
     ORR     temp, temp, #0xC0      // Set IRQ/FIQ flag to disable
     MSR     SPSR_cxsf, temp        // Set SPSR
  }

  interrupts_enabled = 1;
}

void __SWI_9 (void)
{
  //__disable_irq();
  //__disable_fiq();
  int temp;

  __asm
  {
     MRS     temp, SPSR_cxsf        // Get SPSR
     BIC     temp, temp, #0xC0      // Clear IRQ/FIQ flag to enable
     MSR     SPSR_cxsf, temp        // Set SPSR
  }

  interrupts_enabled = 0;
}

This compiles, and I thought it would work, but obviously it doesn't...

I checked the output of the compiler, I don't see any reference (except for comments) to my asm code. Specifically, this is what I get:

                  __SWI_8 PROC
;;;49
;;;50     void __SWI_8 (void)
000084  e59f1040          LDR      r1,|L1.204|
;;;51     {
;;;52       //__enable_irq();
;;;53       //__enable_fiq();
;;;54       int temp;
;;;55
;;;56        __asm
;;;57       {
;;;58          MRS     temp, SPSR             // Get SPSR
;;;59          ORR     temp, temp, #0xC0      // Set IRQ/FIQ flag to disable
;;;60          MSR     SPSR, temp             // Set SPSR
;;;61       }
;;;62
;;;63       interrupts_enabled = 1;
000088  e3a00001          MOV      r0,#1
00008c  e5c10000          STRB     r0,[r1,#0]  ; interrupts_enabled
;;;64     }
000090  e12fff1e          BX       lr
;;;65
                          ENDP

                  __SWI_9 PROC
;;;66     void __SWI_9 (void)
000094  e59f1030          LDR      r1,|L1.204|
;;;67     {
;;;68       //__disable_irq();
;;;69       //__disable_fiq();
;;;70       int temp;
;;;71
;;;72       __asm
;;;73       {
;;;74          MRS     temp, SPSR             // Get SPSR
;;;75          BIC     temp, temp, #0xC0      // Clear IRQ/FIQ flag to enable
;;;76          MSR     SPSR, temp             // Set SPSR
;;;77       }
;;;78
;;;79       interrupts_enabled = 0;
000098  e3a00000          MOV      r0,#0
00009c  e5c10000          STRB     r0,[r1,#0]  ; interrupts_enabled
;;;80     }
0000a0  e12fff1e          BX       lr
;;;81
                          ENDP

Any tips on where I'm wrong? This should be relatively straightforward.

Thanks,
--
George Andrew Brindeiro
Robotron Automation and Technology

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