From: Arnd Bergmann <arnd@arndb.de>
To: Scott Branden <sbranden@broadcom.com>
Cc: bcm-kernel-feedback-list@broadcom.com, Rob Herring <robh+dt@kernel.org>,
        Pawel Moll <pawel.moll@arm.com>, Mark Rutland <mark.rutland@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
        Kumar Gala <galak@codeaurora.org>, Matt Mackall <mpm@selenic.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Grant Likely <grant.likely@linaro.org>, Ray Jui <rjui@broadcom.com>,
        Jonathan Richardson <jonathar@broadcom.com>,
        Dmitry Torokhov <dtor@google.com>, Anatol Pomazao <anatol@google.com>,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] hwrng: iproc-rng200 - Add Broadcom IPROC RNG driver
Date: Wed, 25 Feb 2015 20:17:42 +0100
Message-ID: <3062825.7b1oYP4yuL@wuerfel>
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On Wednesday 25 February 2015 10:16:24 Scott Branden wrote:
> This adds a driver for random number generator present on Broadcom
> IPROC devices.
> 
> Reviewed-by: Ray Jui <rjui@broadcom.com>
> Signed-off-by: Scott Branden <sbranden@broadcom.com>

The driver looks reasonable overall, I have just one question about
something that sticks out:

> +	while ((num_remaining > 0) && time_before(jiffies, idle_endtime)) {
...
> +
> +		/* Are there any random numbers available? */
> +		if ((ioread32(rng_base + RNG_FIFO_COUNT_OFFSET) &
> +				RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK) > 0) {
...
> +		} else {
> +			if (!wait)
> +				/* Cannot wait, return immediately */
> +				return max - num_remaining;
> +
> +			/* Can wait, give others chance to run */
> +			cpu_relax();
> +		}
> +	}
> +

It looks like you do a busy-loop around cpu_relax here if asked to wait.
Is this intentional? I would normally expect either cond_resched() or
some msleep() instead.

	Arnd
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