context.c

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/*
 * $Log: context.c,v $
 *
 */

#include <cfg/os.h>

#include <string.h>

#include <sys/atom.h>
#include <sys/heap.h>
#include <sys/thread.h>

#include <avr32/io.h>



typedef struct {
    uint32_t csf_cpsr;
    uint32_t csf_lr;
    uint32_t csf_r7;
    uint32_t csf_r6;
    uint32_t csf_r5;
    uint32_t csf_r4;
    uint32_t csf_r3;
    uint32_t csf_r2;
    uint32_t csf_r1;
    uint32_t csf_r0;
} SWITCHFRAME;

typedef struct {
    uint32_t cef_pc;
    uint32_t cef_r12;
} ENTERFRAME;

static void NutThreadEntry(void) __attribute__ ((naked));
void NutThreadEntry(void)
{
    /* Load argument in r12 and jump to thread entry. */
    __asm__ volatile ("popm   r12, lr\n\t"      /* put the value of cef_r12 in R12 and the value of cef_pc in lr */
                      "mov    pc,lr\n\t"        /* then pc recieve lr */
                      :::"r12", "lr", "pc");
}


void NutThreadSwitch(void) __attribute__ ((naked));
void NutThreadSwitch(void)
{
    /* Save CPU context. */
    __asm__ volatile ("pushm    r0-r7, lr \n\t"    /* Save registers in the stack */
                      "mfsr       r10, %1 \n\t"    /* Save status in R10 */
                      "pushm      r10     \n\t"    /* Save r10 in the stack */
                      "st.w        %0, sp \n\t"    /* the address contained in R10 contain the address of the stack pointer. */
                      :"=m" (runningThread->td_sp)
                      :"i"(AVR32_SR)
                      :"r10");

    /* Select thread on top of the run queue. */
    runningThread = runQueue;
    runningThread->td_state = TDS_RUNNING;

    /* Restore context. */
    /* When changing this, remember to keep NutThreadCreate copy in sync */
    __asm__ volatile ("ld.w    sp, %0\n\t"         /* Restore stack pointer. */
                      "popm    r10   \n\t"         /* Get saved status... */
                      "mtsr    %1, r10\n\t" "popm r0-r7, lr\n\t"        /* Restore registers. */
                      "mov     pc, lr\n\t"         /* Restore status and return. */
                      ::"m" (runningThread->td_sp), "i"(AVR32_SR)
                      :"r10");

#if defined(NUT_CRITICAL_NESTING) && !defined(NUT_CRITICAL_NESTING_STACK)
    critical_nesting_level = 0;
#endif
}

HANDLE NutThreadCreate(char *name, void (*fn) (void *), void *arg, size_t stackSize)
{
    uint8_t *threadMem;
    SWITCHFRAME *sf;
    ENTERFRAME *ef;
    NUTTHREADINFO *td;

    /*
     * Allocate stack and thread info structure in one block.
     * We sill setup the following layout:
     *
     * Upper memory addresses.
     *
     *              +--------------------+
     *              I                    I
     *              I   NUTTHREADINFO    I
     *              I                    I
     * td ->        +-----+--------------+ <- Stack top
     *              I     I              I
     *              I  T  I   ENTERFRAME I
     *              I  H  I              I
     * ef ->        I  R  +--------------+
     *              I  E  I              I    ^
     *              I  A  I  SWITCHFRAME I    I
     *              I  D  I              I    I  pop moves up
     * sf ->        I     +--------------+ <- Initial stack pointer
     *              I  S  I              I    I  push moves down
     *              I  T  I Application  I    I
     *              I  A  I Stack        I    V
     *              I  C  I              I
     *              I  K  I              I
     * threadMem -> +-----+--------------+ <- Stack bottom
     *
     * Lower memory addresses.
     */
    if ((threadMem = NutHeapAlloc(stackSize + sizeof(NUTTHREADINFO))) == 0) {
        return 0;
    }
    td = (NUTTHREADINFO *) (threadMem + stackSize);
    ef = (ENTERFRAME *) ((uptr_t) td - sizeof(ENTERFRAME));
    sf = (SWITCHFRAME *) ((uptr_t) ef - sizeof(SWITCHFRAME));

    /* 
     * Set predefined values at the stack bottom. May be used to detect
     * stack overflows.
     */
#if defined(NUTDEBUG_CHECK_STACKMIN) || defined(NUTDEBUG_CHECK_STACK)
    {
        uint32_t *fip = (uint32_t *) threadMem;
        while (fip < (uint32_t *) sf) {
            *fip++ = DEADBEEF;
        }
    }
#else
    *((uint32_t *) threadMem) = DEADBEEF;
    *((uint32_t *) (threadMem + 4)) = DEADBEEF;
    *((uint32_t *) (threadMem + 8)) = DEADBEEF;
    *((uint32_t *) (threadMem + 12)) = DEADBEEF;
#endif

    /*
     * Setup the entry frame to simulate C function entry.
     */
    ef->cef_pc = (uptr_t) fn;
    ef->cef_r12 = (uptr_t) arg;

    /*
     * Setup the switch frame.
     */
    sf->csf_lr = (uptr_t) NutThreadEntry;
    sf->csf_cpsr = (AVR32_SR_M_SUP << AVR32_SR_M_OFFSET);       /* [M2:M0]=001 - Supervisor Mode I1M=0 I0M=0, GM=0 */

    /*
     * Initialize the thread info structure and insert it into the 
     * thread list and the run queue.
     */
    memcpy(td->td_name, name, sizeof(td->td_name) - 1);
    td->td_name[sizeof(td->td_name) - 1] = 0;
    td->td_state = TDS_READY;
    td->td_sp = (uptr_t) sf;
    td->td_priority = 64;
    td->td_memory = threadMem;
    td->td_timer = 0;
    td->td_queue = 0;

    NutEnterCritical();
    td->td_next = nutThreadList;
    nutThreadList = td;
    NutThreadAddPriQueue(td, (NUTTHREADINFO **) & runQueue);

    /*
     * If no thread is running, then this is the first thread ever 
     * created. In Nut/OS, the idle thread is created first.
     */
    if (runningThread == 0) {
        /* This will never return. */
        runningThread = runQueue;
        runningThread->td_state = TDS_RUNNING;
        /* Restore context. */
        __asm__ volatile (      /* */
                             "ld.w    sp, %0\n\t"       /* Restore stack pointer. */
                             "popm    r10   \n\t"       /* Get saved status... */
                             "mtsr    %1, r10\n\t" "popm r0-r7, lr\n\t" /* Restore registers. */
                             "mov     pc, lr\n\t"       /* Restore status and return. */
                             ::"m" (runningThread->td_sp), "i"(AVR32_SR)
                             :"r10");
    }

    /*
     * If current context is not in front of the run queue (highest 
     * priority), then switch to the thread in front.
     */
    if (runningThread != runQueue) {
        runningThread->td_state = TDS_READY;
        NutThreadSwitch();
    }
    NutExitCritical();

    return td;
}