No subject

Fri Oct 22 17:57:35 EDT 2010

   clock_gettime( CLOCK_MONOTONIC, &now );

leads me to believe that kernel function ks8695_gettimeoffset() is not worth anything.

I suspect that there really is no "count down" read support on the KS8695 timer register.

The time delta (when it jumps) that I see from clock_gettime() corresponds to the 2 msec system
interrupt HZ tick that I compiled into the kernel.

I think this is a hardware limitation, but wanted another opinion, kernel code for said function has
not changed in years, shown below.

Thank you,


 * Returns number of ms since last clock interrupt.  Note that interrupts
 * will have been disabled by do_gettimeoffset()
static unsigned long ks8695_gettimeoffset (void)
    unsigned long elapsed, tick2, intpending;

     * Get the current number of ticks.  Note that there is a race
     * condition between us reading the timer and checking for an
     * interrupt.  We solve this by ensuring that the counter has not
     * reloaded between our two reads.
    elapsed = __raw_readl(KS8695_TMR_VA + KS8695_T1TC) + __raw_readl(KS8695_TMR_VA + KS8695_T1PD);
    do {
        tick2 = elapsed;
        intpending = __raw_readl(KS8695_IRQ_VA + KS8695_INTST) & (1 << KS8695_IRQ_TIMER1);
        elapsed = __raw_readl(KS8695_TMR_VA + KS8695_T1TC) + __raw_readl(KS8695_TMR_VA + KS8695_T1PD);
    } while (elapsed > tick2);

    /* Convert to number of ticks expired (not remaining) */
    elapsed = (CLOCK_TICK_RATE / HZ) - elapsed;

    /* Is interrupt pending?  If so, then timer has been reloaded already. */
    if (intpending)
        elapsed += (CLOCK_TICK_RATE / HZ);

    /* Convert ticks to usecs */
    return (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;

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