linux-kernel - Re: [PATCH] clockevents/drivers/dw_apb_timer: Implement ->set_state_oneshot

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Message-ID: <20160226095456.GD5823@vireshk-i7>
Date:	Fri, 26 Feb 2016 15:24:56 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Jisheng Zhang <jszhang@...vell.com>
Cc:	daniel.lezcano@...aro.org, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] clockevents/drivers/dw_apb_timer: Implement
 ->set_state_oneshot_stopped()

On 26-02-16, 17:45, Jisheng Zhang wrote:
> The dw_apb_timer only "supports PERIODIC mode and their drivers emulate
> ONESHOT over that" as described in commit 8fff52fd5093 ("clockevents:
> Introduce CLOCK_EVT_STATE_ONESHOT_STOPPED state").
> 
> Inspired by Viresh, I think the dw_apb_timer also needs to implement
> the set_state_oneshot_stopped() which is called by the clkevt core,
> when the next event is required at an expiry time of 'KTIME_MAX'. This
> normally happens with NO_HZ_{IDLE|FULL} in both LOWRES/HIGHRES modes.
> 
> This patch makes the clockevent device to stop on such an event, to
> avoid spurious interrupts, as explained by the above commit.
> 
> Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
> ---
>  drivers/clocksource/dw_apb_timer.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/clocksource/dw_apb_timer.c b/drivers/clocksource/dw_apb_timer.c
> index 6334526..797505a 100644
> --- a/drivers/clocksource/dw_apb_timer.c
> +++ b/drivers/clocksource/dw_apb_timer.c
> @@ -264,6 +264,7 @@ dw_apb_clockevent_init(int cpu, const char *name, unsigned rating,
>  	dw_ced->ced.set_state_shutdown = apbt_shutdown;
>  	dw_ced->ced.set_state_periodic = apbt_set_periodic;
>  	dw_ced->ced.set_state_oneshot = apbt_set_oneshot;
> +	dw_ced->ced.set_state_oneshot_stopped = apbt_shutdown;
>  	dw_ced->ced.tick_resume = apbt_resume;
>  	dw_ced->ced.set_next_event = apbt_next_event;
>  	dw_ced->ced.irq = dw_ced->timer.irq;

Reviewed-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh