From: Romain Perier <romain.perier@free-electrons.com>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: dsaxena@plexity.net, mpm@selenic.com,
Gregory Clement <gregory.clement@free-electrons.com>,
Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
Nadav Haklai <nadavh@marvell.com>, Omri Itach <omrii@marvell.com>,
Shadi Ammouri <shadi@marvell.com>,
Yahuda Yitschak <yehuday@marvell.com>,
Hanna Hawa <hannah@marvell.com>,
Neta Zur Hershkovits <neta@marvell.com>,
Igal Liberman <igall@marvell.com>,
Marcin Wojtas <mw@semihalf.com>,
linux-crypto@vger.kernel.org
Subject: Re: [PATCH v2 3/8] hwrng: omap - Switch to non-obsolete read API implementation
Date: Fri, 16 Sep 2016 12:11:26 +0200 [thread overview]
Message-ID: <57DBC54E.2010102@free-electrons.com> (raw)
In-Reply-To: <20160913094825.GA30645@gondor.apana.org.au>
Hi,
Le 13/09/2016 11:48, Herbert Xu a écrit :
> On Wed, Sep 07, 2016 at 05:57:38PM +0200, Romain Perier wrote:
>> +
>> +static int omap_rng_do_read(struct hwrng *rng, void *data, size_t max,
>> + bool wait)
>> {
>> struct omap_rng_dev *priv;
>> - int data, i;
>>
>> priv = (struct omap_rng_dev *)rng->priv;
>>
>> - for (i = 0; i < 20; i++) {
>> - data = priv->pdata->data_present(priv);
>> - if (data || !wait)
>> - break;
>> - /* RNG produces data fast enough (2+ MBit/sec, even
>> - * during "rngtest" loads, that these delays don't
>> - * seem to trigger. We *could* use the RNG IRQ, but
>> - * that'd be higher overhead ... so why bother?
>> - */
>> - udelay(10);
>
> So in the wait case you're changing the driver's behaviour. Instead
> of waiting for 1us you'll now wait for 1s if there is no data. Is
> this what really what you want?
>
> Cheers,
>
Mhhh, you're right, in this specific case it will add more latency...
with busy loop, on average, 20 retries will be enough to have data...
Thanks!
--
Romain Perier, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
next prev parent reply other threads:[~2016-09-16 10:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-07 15:57 [PATCH v2 0/8] Add support for SafeXcel IP-76 to OMAP RNG Romain Perier
2016-09-07 15:57 ` [PATCH v2 1/8] dt-bindings: Add vendor prefix for INSIDE Secure Romain Perier
2016-09-07 15:57 ` [PATCH v2 2/8] dt-bindings: omap-rng: Document SafeXcel IP-76 device variant Romain Perier
2016-09-07 15:57 ` [PATCH v2 3/8] hwrng: omap - Switch to non-obsolete read API implementation Romain Perier
2016-09-13 9:48 ` Herbert Xu
2016-09-16 10:11 ` Romain Perier [this message]
2016-09-07 15:57 ` [PATCH v2 4/8] hwrng: omap - Remove global definition of hwrng Romain Perier
2016-09-07 15:57 ` [PATCH v2 5/8] hwrng: omap - Add support for 128-bit output of data Romain Perier
2016-09-07 15:57 ` [PATCH v2 6/8] hwrng: omap - Don't prefix the probe message with OMAP Romain Perier
2016-09-07 15:57 ` [PATCH v2 7/8] hwrng: omap - Add device variant for SafeXcel IP-76 found in Armada 8K Romain Perier
2016-09-07 15:57 ` [PATCH v2 8/8] arm64: dts: marvell: add TRNG description for Armada 8K CP Romain Perier
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