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Cortex-M3 HAL interrupt-priority code bug
- From: Nagaraj K <nagaraj dot kmurthy at gmail dot com>
- To: ecos-devel at ecos dot sourceware dot org
- Date: Thu, 25 Nov 2010 16:04:25 +0530
- Subject: Cortex-M3 HAL interrupt-priority code bug
Hi,
I was browsing through the Cortex-M3 HAL port and everything looks
OK except for the function
hal_interrupt_set_level() in hal\cortexm\arch\current\src\hal_misc.c
Here is the original function.
__externC void hal_interrupt_set_level( cyg_uint32 vector, cyg_uint32 level )
{
cyg_uint32 l = (level)+CYGNUM_HAL_CORTEXM_PRIORITY_MAX;
if( l > 0xFF ) l = 0xFF; /* clamp to 0xFF */
if( vector >= CYGNUM_HAL_INTERRUPT_EXTERNAL &&
vector <= CYGNUM_HAL_INTERRUPT_NVIC_MAX )
{
HAL_WRITE_UINT8(
CYGARC_REG_NVIC_BASE+CYGARC_REG_NVIC_PR(vector-CYGNUM_HAL_INTERRUPT_EXTERNAL),
l );
}
else if ( vector == CYGNUM_HAL_INTERRUPT_SYS_TICK )
{
cyg_uint32 shpr2;
HAL_READ_UINT32( CYGARC_REG_NVIC_BASE+CYGARC_REG_NVIC_SHPR2, shpr2 );
shpr2 &= ~0xFF000000;
shpr2 |= (l)<<24;
HAL_WRITE_UINT32( CYGARC_REG_NVIC_BASE+CYGARC_REG_NVIC_SHPR2, shpr2 );
}
HAL_VAR_INTERRUPT_SET_LEVEL( vector, level );
}
I see that this function wrongly implements the priority level in
Cortex-M3 processor. According to the Cortex-M3 data sheet, we need to
write the priority level to the top N bits of the register where N is
the number of priority level bits implemented in this particular
version of the cortex variant. Hence I feel that the right
implementation should be
__externC void hal_interrupt_set_level( cyg_uint32 vector, cyg_uint32 level )
{
cyg_uint32 l = (level)<<(8-CYGNUM_HAL_CORTEXM_PRIORITY_LEVEL_BITS);
if( l > 0xFF ) l = 0xFF; /* clamp to 0xFF */
if( vector >= CYGNUM_HAL_INTERRUPT_EXTERNAL &&
vector <= CYGNUM_HAL_INTERRUPT_NVIC_MAX )
{
HAL_WRITE_UINT8(
CYGARC_REG_NVIC_BASE+CYGARC_REG_NVIC_PR(vector-CYGNUM_HAL_INTERRUPT_EXTERNAL),
l );
}
else if ( vector == CYGNUM_HAL_INTERRUPT_SYS_TICK )
{
cyg_uint32 shpr2;
HAL_READ_UINT32( CYGARC_REG_NVIC_BASE+CYGARC_REG_NVIC_SHPR2, shpr2 );
shpr2 &= ~0xFF000000;
shpr2 |= (level)<<24;
HAL_WRITE_UINT32( CYGARC_REG_NVIC_BASE+CYGARC_REG_NVIC_SHPR2, shpr2 );
}
HAL_VAR_INTERRUPT_SET_LEVEL( vector, level );
}
I am new to this developer forum and I am sorry if this is not the
right mailing list for this discussion. If so, please suggest an
alternate forum.
Thanks & Regards, Nagaraj