port.c

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/****************************************************************************/
 
#include "port.h"
#include "thread.h"
#include "core.h"
#include "config.h"
 
#include "stm32l1xx.h"

void akos_port_systick_init_freq(uint32_t cpu_freq)
{
    volatile uint32_t ticks = cpu_freq / 1000u;
 
    SysTick->LOAD = ticks - 1u;
    SysTick->VAL = 0u;
    SysTick->CTRL = SysTick_CTRL_CLKSOURCE_Msk |
            SysTick_CTRL_TICKINT_Msk |
            SysTick_CTRL_ENABLE_Msk;
 
    *(volatile uint32_t *)0xE000ED20UL &= ~(0xFFUL << 24);
    *(volatile uint32_t *)0xE000ED20UL |= ((uint32_t)1u << (8U - __NVIC_PRIO_BITS)) << 24;
}

void akos_port_start_first_task(void)
{
    __asm volatile(
        " ldr r0, =0xE000ED08       \n" /* Use the NVIC offset register to locate the stack. */
        " ldr r0, [r0]              \n"
        " ldr r0, [r0]              \n"
        " msr msp, r0               \n" /* Set the msp back to the start of the stack. */
        " cpsie i                   \n" /* Globally enable interrupts. */
        " cpsie f                   \n"
        " dsb                       \n"
        " isb                       \n"
        " svc 0                     \n" /* System call to start first thread. */
        " nop                       \n"
        " .ltorg                    \n"
    );
}

uint32_t *akos_port_task_stack_init(uint32_t *p_stack,
                               size_t stack_size,
                               void (*pf_task)(void *),
                               void *p_arg)
{
    uint32_t *p_stack_ptr;
 
    p_stack_ptr = &p_stack[stack_size - (uint32_t)1];
    p_stack_ptr = (uint32_t *)(((uint32_t)p_stack_ptr) & (~((uint32_t)0x007)));
 
    *(--p_stack_ptr) = (uint32_t)0x01000000UL;
    *(--p_stack_ptr) = ((uint32_t)pf_task) & ((uint32_t)0xfffffffeUL);
    *(--p_stack_ptr) = (uint32_t)0x0000000EUL;
    p_stack_ptr -= 5;
    *p_stack_ptr = (uint32_t)p_arg;
    p_stack_ptr -= 8;
 
    return p_stack_ptr;
}
 
#ifdef __cplusplus
extern "C"
{
#endif
    void port_SVCHandler(void)
    {
        __asm volatile(
            "CPSID   I                      \n" // Prevent interruption during context switch
            "LDR     R1, =tcb_curr_ptr      \n" // get pointer to TCB current
            "LDR     R1, [R1]               \n" // get TCB current  = pointer to StkPtr
            "LDR     R0, [R1]               \n" // get StkPtr
            "LDMIA R0!, {R4-R11}            \n" //
            "MSR     PSP, R0                \n" //
            "ORR LR, #0xD                   \n" // LR = 0xFFFFFFFD return to threadmode
            "CPSIE   I                      \n" //
            "BX      LR                     \n" //
        );
    }
#ifdef __cplusplus
}
#endif
 
#ifdef __cplusplus
extern "C"
{
#endif
    void port_PendSVHandler(void)
    {
        __asm volatile(
            //"CPSID   I                                \n" //Prevent interruption during context switch
            "MRS     R0, PSP                            \n" // PSP is process stack pointer
            "CBZ     R0, OS_CPU_PendSVHandler_nosave    \n" // Skip register save the first time
 
            "SUBS    R0, R0, #0x20                      \n" // Save remaining regs r4-11 on process stack
            "STM     R0, {R4-R11}                       \n" //
 
            "LDR     R1, =tcb_curr_ptr                  \n" // OSTCBCur->OSTCBStkPtr = SP;
            "LDR     R1, [R1]\n"                            //
            "STR     R0, [R1]                           \n" // R0 is SP of process being switched out
 
            /* At this point, entire context of process has been saved  */
 
            "OS_CPU_PendSVHandler_nosave:               \n" //
            "LDR     R0, =tcb_curr_ptr                  \n" // OSTCBCur  = OSTCBHighRdy;
            "LDR     R1, =tcb_high_rdy_ptr              \n" //
            "LDR     R2, [R1]                           \n" //
            "STR     R2, [R0]                           \n" //
 
            "LDR     R0, [R2]                           \n" // R0 is new process SP; SP = OSTCBHighRdy->OSTCBStkPtr;
            "LDM     R0, {R4-R11}                       \n" // Restore r4-11 from new process stack
            "ADDS    R0, R0, #0x20                      \n" //
            "MSR     PSP, R0                            \n" // Load PSP with new process SP
            "ORR     LR, LR, #0x04                      \n" // Ensure exception return uses process stack
            //"CPSIE   I                                \n"     //
            "BX      LR                                 \n" // Exception return will restore remaining context
        );
    }
#ifdef __cplusplus
}
#endif
 
#ifdef __cplusplus
extern "C"
{
#endif
    void port_SysTickHandler()
    {
        port_disable_interrupts
        /* Increment the RTOS tick. */
        if (akos_thread_increment_tick() == OS_TRUE)
        {
            /* A context switch is required.  Context switching is performed in
             * the PendSV interrupt.  Pend the PendSV interrupt. */
            port_trigger_PendSV();
        }
        port_enable_interrupts
    }
 
#ifdef __cplusplus
}
#endif