linux-kernel - Re: [PATCH v3 02/10] clocksource:arm_global

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Message-Id: <201306202102.30478.arnd@arndb.de>
Date:	Thu, 20 Jun 2013 21:02:30 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Srinivas KANDAGATLA <srinivas.kandagatla@...com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Rob Landley <rob@...dley.net>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Russell King <linux@....linux.org.uk>,
	Stuart Menefy <stuart.menefy@...com>,
	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
	kernel@...inux.com, linux-serial@...r.kernel.org,
	Mark Brown <broonie@...nel.org>,
	Stephen Gallimore <stephen.gallimore@...com>,
	Rob Herring <robherring2@...il.com>,
	Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v3 02/10] clocksource:arm_global_timer: Add ARM global timer support.

On Thursday 20 June 2013, Srinivas KANDAGATLA wrote:
> +static u64 gt_counter_read(void)
> +{
> +       u64 counter;
> +       u32 lower;
> +       u32 upper, old_upper;
> +
> +       upper = __raw_readl(gt_base + GT_COUNTER1);
> +       do {
> +               old_upper = upper;
> +               lower = __raw_readl(gt_base + GT_COUNTER0);
> +               upper = __raw_readl(gt_base + GT_COUNTER1);
> +       } while (upper != old_upper);
> +
> +       counter = upper;
> +       counter <<= 32;
> +       counter |= lower;
> +       return counter;
> +}

Please replace __raw_readl etc with the non-__raw variants
throughout the code.

The __raw accessors are not endian safe and are not meant
for device drivers. If you are worried about latency from
extra barriers, use readl_relaxed().

	Arnd
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