Re: [RFC PATCH v4 04/21] x86/hpet: Add hpet_set_comparator() for periodic and one-shot modes

Thomas Gleixner
2019-06-14T18:17:42Z

On Thu, 23 May 2019, Ricardo Neri wrote:
> +/**
> + * hpet_set_comparator() - Helper function for setting comparator register
> + * @num: The timer ID
> + * @cmp: The value to be written to the comparator/accumulator
> + * @period: The value to be written to the period (0 = oneshot mode)
> + *
> + * Helper function for updating comparator, accumulator and period values.
> + *
> + * In periodic mode, HPET needs HPET_TN_SETVAL to be set before writing
> + * to the Tn_CMP to update the accumulator. Then, HPET needs a second
> + * write (with HPET_TN_SETVAL cleared) to Tn_CMP to set the period.
> + * The HPET_TN_SETVAL bit is automatically cleared after the first write.
> + *
> + * For one-shot mode, HPET_TN_SETVAL does not need to be set.
> + *
> + * See the following documents:
> + * - Intel IA-PC HPET (High Precision Event Timers) Specification
> + * - AMD-8111 HyperTransport I/O Hub Data Sheet, Publication # 24674
> + */
> +void hpet_set_comparator(int num, unsigned int cmp, unsigned int period)
> +{
> + if (period) {
> + unsigned int v = hpet_readl(HPET_Tn_CFG(num));
> +
> + hpet_writel(v | HPET_TN_SETVAL, HPET_Tn_CFG(num));
> + }
> +
> + hpet_writel(cmp, HPET_Tn_CMP(num));
> +
> + if (!period)
> + return;

TBH, I hate this conditional handling. What's wrong with two functions?

> +
> + /*
> + * This delay is seldom used: never in one-shot mode and in periodic
> + * only when reprogramming the timer.
> + */
> + udelay(1);
> + hpet_writel(period, HPET_Tn_CMP(num));
> +}
> +EXPORT_SYMBOL_GPL(hpet_set_comparator);

Why is this exported? Which module user needs this?

Thanks,

tglx