linux-kernel - Re: [PATCH v4] ARM: clocksource: add support for MOXA ART SoCs

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Date:	Mon, 1 Jul 2013 19:55:15 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jonas Jensen <jonas.jensen@...il.com>
cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	arm@...nel.org, john.stultz@...aro.org,
	u.kleine-koenig@...gutronix.de, tomasz.figa@...il.com,
	linus.walleij@...aro.org, thomas.petazzoni@...e-electrons.com,
	arnd@...db.de
Subject: Re: [PATCH v4] ARM: clocksource: add support for MOXA ART SoCs

On Mon, 1 Jul 2013, Jonas Jensen wrote:
> +static int moxart_clkevt_next_event(unsigned long cycles,
> +				    struct clock_event_device *unused)
> +{
> +	u32 u;
> +
> +	u = readl(base + TIMER_CR) & ~TIMEREG_CR_1_ENABLE;

You should cache that value and avoid another readout below. You could
even cache it in general so you avoid all readouts.

> +	writel(u, base + TIMER_CR);
> +	u = readl(base + TIMER1_BASE + REG_COUNT) - cycles;
> +	writel(u, base + TIMER1_BASE + REG_MATCH1);
> +	u = readl(base + TIMER_CR) | TIMEREG_CR_1_ENABLE;
> +	writel(u, base + TIMER_CR);
> +	return 0;
> +}

Thanks,

	tglx
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