[PATCH 1/3] ARM: CSR: Adding CSR SiRFprimaII board support

[Barry Song]

2011/7/6 Russell King - ARM Linux <linux at arm.linux.org.uk>:
> On Wed, Jul 06, 2011 at 02:47:56AM -0700, Barry Song wrote:
>> +static int sirfsoc_timer_set_next_event(unsigned long delta,
>> +     struct clock_event_device *ce)
>> +{
>> +     unsigned long now, next;
>> +
>> +     writel_relaxed(SIRFSOC_TIMER_LATCH_BIT, sirfsoc_timer_base + SIRFSOC_TIMER_LATCH);
>> +     now = readl_relaxed(sirfsoc_timer_base + SIRFSOC_TIMER_LATCHED_LO);
>> +     do {
>> +             next = now + delta;
>> +             writel_relaxed(next, sirfsoc_timer_base + SIRFSOC_TIMER_MATCH_0);
>> +             writel_relaxed(SIRFSOC_TIMER_LATCH_BIT, sirfsoc_timer_base + SIRFSOC_TIMER_LATCH);
>> +             now = readl_relaxed(sirfsoc_timer_base + SIRFSOC_TIMER_LATCHED_LO);
>> +     } while ((next - now) > delta);
>> +
>> +     return 0;
>> +}
>
> Please have a look at any of the callsites of clockevents_program_event()
> in kernel/time/.  You'll notice that they loop in some fashion should your
> set_next_event() return -ETIME.

ok. looks like the function can be fixed to:

static int sirfsoc_timer_set_next_event(unsigned long delta,
                struct clock_event_device *ce)
{
        unsigned long now, next;

        writel_relaxed(SIRFSOC_TIMER_LATCH_BIT, sirfsoc_timer_base +
SIRFSOC_TIMER_LATCH);
        now = readl_relaxed(sirfsoc_timer_base + SIRFSOC_TIMER_LATCHED_LO);

        next = now + delta;
        writel_relaxed(next, sirfsoc_timer_base + SIRFSOC_TIMER_MATCH_0);
        writel_relaxed(SIRFSOC_TIMER_LATCH_BIT, sirfsoc_timer_base +
SIRFSOC_TIMER_LATCH);
        now = readl_relaxed(sirfsoc_timer_base + SIRFSOC_TIMER_LATCHED_LO);

        return next - now > delta ? -ETIME : 0;
}


>
> As there is the possibility that if you can't program the event (because
> it has already passed) then it is likely that there is some work which
> needs to be done before the next event is set.  So the repeat logic should
> stay in the common code and not be duplicated in each platform.
>
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