clkinit.c

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/* clkinit.c - clkinit (BeagleBone Black) */

#include <xinu.h>

uint32 clktime;   /* Seconds since boot         */
uint32 count1000; /* ms since last clock tick             */
qid16 sleepq;     /* Queue of sleeping processes        */
uint32 preempt;

/*------------------------------------------------------------------------
 * clkinit  -  Initialize the clock and sleep queue at startup
 *------------------------------------------------------------------------
 */
void clkinit(void)
{
    volatile struct am335x_timer1ms *csrptr =
        (volatile struct am335x_timer1ms *)AM335X_TIMER1MS_ADDR;
    /* Pointer to timer CSR in BBoneBlack   */
    volatile uint32 *clkctrl =
        (volatile uint32 *)AM335X_TIMER1MS_CLKCTRL_ADDR;

    *clkctrl = AM335X_TIMER1MS_CLKCTRL_EN;
    while ((*clkctrl) != 0x2) /* Do nothing */
        ;

    /* Reset the timer module */

    csrptr->tiocp_cfg |= AM335X_TIMER1MS_TIOCP_CFG_SOFTRESET;

    /* Wait until the reset is complete */

    while ((csrptr->tistat & AM335X_TIMER1MS_TISTAT_RESETDONE) == 0)
        /* Do nothing */;

    /* Set interrupt vector for clock to invoke clkint */

    set_evec(AM335X_TIMER1MS_IRQ, (uint32)clkhandler);

    sleepq = newqueue(); /* Allocate a queue to hold the delta  */
                         /*   list of sleeping processes        */

    preempt = QUANTUM; /* Set the preemption time       */

    clktime = 0; /* Start counting seconds      */
    count1000 = 0;
    /* The following values are calculated for a    */
    /*   timer that generates 1ms tick rate     */

    csrptr->tpir = 1000000;
    csrptr->tnir = 0;
    csrptr->tldr = 0xFFFFFFFF - 26000;

    /* Set the timer to auto reload */

    csrptr->tclr = AM335X_TIMER1MS_TCLR_AR;

    /* Start the timer */

    csrptr->tclr |= AM335X_TIMER1MS_TCLR_ST;

    /* Enable overflow interrupt which will generate */
    /*   an interrupt every 1 ms             */

    csrptr->tier = AM335X_TIMER1MS_TIER_OVF_IT_ENA;

    /* Kickstart the timer */

    csrptr->ttgr = 1;

    return;
}