linux-kernel - Re: [PATCH 4/7] clocksource/cadence_ttc: Adjust interval in clock notifier

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Date:	Tue, 12 Nov 2013 17:29:45 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Soren Brinkmann <soren.brinkmann@...inx.com>,
	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Russell King <linux@....linux.org.uk>,
	Michal Simek <michal.simek@...inx.com>,
	Thomas Gleixner <tglx@...utronix.de>
CC:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH 4/7] clocksource/cadence_ttc: Adjust interval in clock
 notifier

On 11/08/2013 10:21 PM, Soren Brinkmann wrote:
> The clockevent has to be reprogrammed if the timer's input
> clock frequency changes and the timer is in periodic mode, in order to
> maintain the correct timer interval.
>
> Signed-off-by: Soren Brinkmann <soren.brinkmann@...inx.com>
> ---
>   drivers/clocksource/cadence_ttc_timer.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/clocksource/cadence_ttc_timer.c b/drivers/clocksource/cadence_ttc_timer.c
> index a92350b55d32..68a336038d8f 100644
> --- a/drivers/clocksource/cadence_ttc_timer.c
> +++ b/drivers/clocksource/cadence_ttc_timer.c
> @@ -338,6 +338,10 @@ static int ttc_rate_change_clockevent_cb(struct notifier_block *nb,
>   		/* update cached frequency */
>   		ttc->freq = ndata->new_rate;
>
> +		if (ttcce->ce.mode == CLOCK_EVT_MODE_PERIODIC)
> +			ttc_set_interval(ttc, DIV_ROUND_CLOSEST(ttc->freq,
> +						PRESCALE * HZ));
> +

Couldn't be racy ?

>   		/* fall through */
>   	}
>   	case PRE_RATE_CHANGE:
>


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