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Improve how the scheduler is started in the GCC Cortex-M0 port.

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This commit is contained in:
Richard Barry 2013-10-22 09:50:20 +00:00
parent f64acd6a48
commit 41fe693968
1 changed files with 23 additions and 33 deletions
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44
FreeRTOS/Source/portable/GCC/ARM_CM0/port.c
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@ -110,7 +110,7 @@ static void prvSetupTimerInterrupt( void );
*/
void xPortPendSVHandler( void ) __attribute__ (( naked ));
void xPortSysTickHandler( void );
void vPortSVCHandler( void ) __attribute__ (( naked ));
void vPortSVCHandler( void );
/*
* Start first task is a separate function so it can be tested in isolation.
@ -161,29 +161,8 @@ static void prvTaskExitError( void )
void vPortSVCHandler( void )
{
__asm volatile (
" ldr r3, pxCurrentTCBConst2 \n" /* Restore the context. */
" ldr r1, [r3] \n" /* Use pxCurrentTCBConst to get the pxCurrentTCB address. */
" ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */
" add r0, r0, #16 \n" /* Move to the high registers. */
" ldmia r0!, {r4-r7} \n" /* Pop the high registers. */
" mov r8, r4 \n"
" mov r9, r5 \n"
" mov r10, r6 \n"
" mov r11, r7 \n"
" \n"
" msr psp, r0 \n" /* Remember the new top of stack for the task. */
" \n"
" sub r0, r0, #32 \n" /* Go back for the low registers that are not automatically restored. */
" ldmia r0!, {r4-r7} \n" /* Pop low registers. */
" mov r1, r14 \n" /* OR R14 with 0x0d. */
" movs r0, #0x0d \n"
" orr r1, r0 \n"
" bx r1 \n"
" \n"
" .align 2 \n"
"pxCurrentTCBConst2: .word pxCurrentTCB \n"
);
/* This function is no longer used, but returned for backward
compatibility. */
}
/*-----------------------------------------------------------*/
@ -193,9 +172,20 @@ void vPortStartFirstTask( void )
table offset register that can be used to locate the initial stack value.
Not all M0 parts have the application vector table at address 0. */
__asm volatile(
" cpsie i \n" /* Globally enable interrupts. */
" svc 0 \n" /* System call to start first task. */
" nop \n"
" ldr r2, pxCurrentTCBConst2 \n" /* Obtain location of pxCurrentTCB. */
" ldr r3, [r2] \n"
" ldr r0, [r3] \n" /* The first item in pxCurrentTCB is the task top of stack. */
" add r0, #32 \n" /* Discard everything up to r0. */
" msr psp, r0 \n" /* This is now the new top of stack to use in the task. */
" movs r0, #2 \n" /* Switch to the psp stack. */
" msr CONTROL, r0 \n"
" pop {r0-r5} \n" /* Pop the registers that are saved automatically. */
" mov lr, r5 \n" /* lr is now in r5. */
" cpsie i \n" /* The first task has its context and interrupts can be enabled. */
" pop {pc} \n" /* Finally, pop the PC to jump to the user defined task code. */
" \n"
" .align 2 \n"
"pxCurrentTCBConst2: .word pxCurrentTCB "
);
}
/*-----------------------------------------------------------*/