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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 xPortPendSVHandler( void ) __attribute__ (( naked ));
void xPortSysTickHandler( void ); 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. * 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 ) void vPortSVCHandler( void )
{ {
__asm volatile ( /* This function is no longer used, but returned for backward
" ldr r3, pxCurrentTCBConst2 \n" /* Restore the context. */ compatibility. */
" 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"
);
} }
/*-----------------------------------------------------------*/ /*-----------------------------------------------------------*/
@ -193,9 +172,20 @@ void vPortStartFirstTask( void )
table offset register that can be used to locate the initial stack value. 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. */ Not all M0 parts have the application vector table at address 0. */
__asm volatile( __asm volatile(
" cpsie i \n" /* Globally enable interrupts. */ " ldr r2, pxCurrentTCBConst2 \n" /* Obtain location of pxCurrentTCB. */
" svc 0 \n" /* System call to start first task. */ " ldr r3, [r2] \n"
" nop \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 "
); );
} }
/*-----------------------------------------------------------*/ /*-----------------------------------------------------------*/