linux-kernel - Re: [PATCH 4/4] hwrng: bcm2835: Read as much data as available

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Date:	Mon, 23 May 2016 19:21:00 -0700
From:	Eric Anholt <eric@...olt.net>
To:	Yendapally Reddy Dhananjaya Reddy <yendapally.reddy@...adcom.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Lee Jones <lee@...nel.org>,
	Russell King <linux@....linux.org.uk>,
	Ray Jui <rjui@...adcom.com>,
	Scott Branden <sbranden@...adcom.com>,
	Jon Mason <jonmason@...adcom.com>,
	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Daniel Thompson <daniel.thompson@...aro.org>,
	Kieran Bingham <kieranbingham@...il.com>,
	Pankaj Dev <pankaj.dev@...com>,
	Richard Weinberger <richard@....at>, noltari@...il.com,
	Joshua Henderson <joshua.henderson@...rochip.com>
Cc:	devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	bcm-kernel-feedback-list@...adcom.com,
	linux-crypto@...r.kernel.org,
	Yendapally Reddy Dhananjaya Reddy 
	<yendapally.reddy@...adcom.com>
Subject: Re: [PATCH 4/4] hwrng: bcm2835: Read as much data as available

Yendapally Reddy Dhananjaya Reddy <yendapally.reddy@...adcom.com>
writes:

> Read the requested number of data from the fifo
>
> Signed-off-by: Yendapally Reddy Dhananjaya Reddy <yendapally.reddy@...adcom.com>
> ---
>  drivers/char/hw_random/bcm2835-rng.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c
> index b1e8b78..9bbdc07 100644
> --- a/drivers/char/hw_random/bcm2835-rng.c
> +++ b/drivers/char/hw_random/bcm2835-rng.c
> @@ -43,6 +43,8 @@ static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
>  			       bool wait)
>  {
>  	void __iomem *rng_base = (void __iomem *)rng->priv;
> +	u32 max_words = max/sizeof(u32);

Style fix: Binary operators get a space on each side, so
"max / sizeof(u32);"

> @@ -50,8 +52,14 @@ static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
>  		cpu_relax();
>  	}
>  
> -	*(u32 *)buf = __raw_readl(rng_base + RNG_DATA);
> -	return sizeof(u32);
> +	num_words = (readl(rng_base + RNG_STATUS) >> 24);

Optional cleanup: here and in the return statement, drop the extra
parenthesis.

Functionality-wise, this patch looks great to me, and should make the
driver more efficient.  With at least the binary operators change done,
it will be:

Reviewed-by: Eric Anholt <eric@...olt.net>

Thanks!

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