Hi James,
On Wednesday 05 December 2012 09:38 PM, James Hogan wrote:
> +static unsigned int hwtimer_freq = HARDWARE_FREQ;
> +static DEFINE_PER_CPU(struct clock_event_device, local_clockevent);
> +static DEFINE_PER_CPU(char [11], local_clockevent_name);
> +void __cpuinit local_timer_setup(unsigned int cpu)
> +{
> + unsigned int txdivtime;
> + struct clock_event_device *clk = &per_cpu(local_clockevent, cpu);
> + char *name = per_cpu(local_clockevent_name, cpu);
> +
> + txdivtime = TBI_GETREG(TXDIVTIME);
> +
> + txdivtime &= ~TXDIVTIME_DIV_BITS;
> + txdivtime |= (HARDWARE_DIV & TXDIVTIME_DIV_BITS);
> +
> + TBI_SETREG(TXDIVTIME, txdivtime);
> +
> + sprintf(name, "META %d", cpu);
> + clk->name = name;
> + clk->features = CLOCK_EVT_FEAT_ONESHOT,
> +
> + clk->rating = 200,
> + clk->shift = 12,
> + clk->irq = TBID_SIGNUM_TRT,
> + clk->set_mode = metag_timer_set_mode,
> + clk->set_next_event = metag_timer_set_next_event,
> +
> + clk->mult = div_sc(hwtimer_freq, NSEC_PER_SEC, clk->shift);
> + clk->max_delta_ns = clockevent_delta2ns(0x7fffffff, clk);
> + clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
> + clk->cpumask = cpumask_of(cpu);
> +
> + clockevents_register_device(clk);
> +
> + /*
> + * For all non-boot CPUs we need to synchronize our free
> + * running clock (TXTIMER) with the boot CPU's clock.
> + *
> + * While this won't be accurate, it should be close enough.
> + */
> + if (cpu) {
> + unsigned int thread0 = cpu_2_hwthread_id[0];
> + unsigned long val;
> +
> + val = core_reg_read(TXUCT_ID, TXTIMER_REGNUM, thread0);
> +
> + asm volatile("MOV TXTIMER, %0\n" : : "r" (val));
> + }
> +}
> +
> +void __init time_init(void)
> +{
> + /*
> + * On Meta 2 SoCs, the actual frequency of the timer is based on the
> + * Meta core clock speed divided by an integer, so it is only
> + * approximately 1MHz. Calculating the real frequency here drastically
> + * reduces clock skew on these SoCs.
> + */
> +#ifdef CONFIG_METAG_META21
> + hwtimer_freq = get_coreclock() / (metag_in32(EXPAND_TIMER_DIV) + 1);
> +#endif
> + clocksource_register_hz(&clocksource_metag, hwtimer_freq);
> +
> + setup_irq(TBID_SIGNUM_TRT, &metag_timer_irq);
> +
> + local_timer_setup(smp_processor_id());
> +}
I have a kludge in ARC port in this subsystem - which I hope you could help clear.
ARC also has a local timer device used for clockevent on each CPU. A one-time
setup_irq() with IRQF_PERCPU - would indeed setup the generic IRQ subsystem - for
making registration effective for all CPUs. However don't you need some per-cpu
magic - say enabling the IRQ at cpu or embedded interrupt controller level -
assuming you starts off with all IRQs disabled (which ARC Linux does).
So we end up using different APIs - request_percpu_irq() as equivalent of
setup_irq() on boot-cpu only and then each CPU calling enable_percpu_irq() to do
the local magic. request_percpu_irq() in turn requires an apriori call to
irq_set_percpu_devid().
https://lkml.org/lkml/2012/11/7/128
Do don't seem to be requiring all of this hence I'm wondering how it works for you!
-Vineet
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