linux-kernel - Re: [PATCH] i.MX31: mxc-rnga: implement waiting for data in driver

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Message-ID: <CAOMZO5BGVa0HRKqv9nKQUy9iGnQ3FV_6OnguMyk3rAinaJkb6w@mail.gmail.com>
Date:	Tue, 21 Feb 2012 11:29:07 -0200
From:	Fabio Estevam <festevam@...il.com>
To:	Michael Thalmeier <michael.thalmeier@...e.at>
Cc:	Matt Mackall <mpm@...enic.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	linux-arm-kernel@...ts.infradead.org, michael@...lmeier.at,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i.MX31: mxc-rnga: implement waiting for data in driver

On Tue, Feb 21, 2012 at 10:13 AM, Michael Thalmeier
<michael.thalmeier@...e.at> wrote:

> -static int mxc_rnga_data_present(struct hwrng *rng)
> +static int mxc_rnga_data_present(struct hwrng *rng, int wait)

This looks good, but ...

>  {
> -       int level;
> +       int level, i;
>        void __iomem *rng_base = (void __iomem *)rng->priv;
>
> -       /* how many random numbers is in FIFO? [0-16] */
> -       level = ((__raw_readl(rng_base + RNGA_STATUS) &
> -                       RNGA_STATUS_LEVEL_MASK) >> 8);
> +       for (i = 0; i < 20; i++) {

Why the magic "20" here?

It would be better to add a proper timeout mechanism instead, such as
time_after(jiffies, timeout)
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