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SubjectRe: [PATCH] clocksource: exynos_mct: Fix stall after CPU hotplugging
Hi Krzysztof,

Two comments inline.

On 25.03.2014 11:41, Krzysztof Kozlowski wrote:

[snip]

> diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
> index 48f76bc05da0..0b49b09dd1a9 100644
> --- a/drivers/clocksource/exynos_mct.c
> +++ b/drivers/clocksource/exynos_mct.c
> @@ -339,7 +339,14 @@ static void exynos4_mct_tick_start(unsigned long cycles,
> static int exynos4_tick_set_next_event(unsigned long cycles,
> struct clock_event_device *evt)
> {
> - struct mct_clock_event_device *mevt = this_cpu_ptr(&percpu_mct_tick);
> + /*
> + * In case of hotplugging non-boot CPU, the set_next_event could be
> + * called on CPU0 by ISR before IRQ affinity is set to proper CPU.

Hmm, is this a desired behavior? I guess this is a question for Thomas
and Daniel.

> + * Thus for accessing proper MCT Lx timer, 'per_cpu' for cpumask
> + * in event must be used instead of 'this_cpu_ptr'.
> + */
> + struct mct_clock_event_device *mevt = &per_cpu(percpu_mct_tick,
> + cpumask_first(evt->cpumask));
>
> exynos4_mct_tick_start(cycles, mevt);
>
> @@ -371,23 +378,13 @@ static inline void exynos4_tick_set_mode(enum clock_event_mode mode,
>
> static int exynos4_mct_tick_clear(struct mct_clock_event_device *mevt)
> {
> - struct clock_event_device *evt = &mevt->evt;
> -
> - /*
> - * This is for supporting oneshot mode.
> - * Mct would generate interrupt periodically
> - * without explicit stopping.
> - */
> - if (evt->mode != CLOCK_EVT_MODE_PERIODIC)
> - exynos4_mct_tick_stop(mevt);
> -
> /* Clear the MCT tick interrupt */
> if (__raw_readl(reg_base + mevt->base + MCT_L_INT_CSTAT_OFFSET) & 1) {
> exynos4_mct_write(0x1, mevt->base + MCT_L_INT_CSTAT_OFFSET);
> return 1;
> - } else {
> - return 0;
> }
> +
> + return 0;

Nobody seems to be checking return value of this function (and I don't
see what it could be used for anyway), so I guess it could be simply
made void.

Best regards,
Tomasz


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