Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753232AbbBYTSx (ORCPT ); Wed, 25 Feb 2015 14:18:53 -0500 Received: from mout.kundenserver.de ([212.227.126.187]:62245 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752739AbbBYTSv (ORCPT ); Wed, 25 Feb 2015 14:18:51 -0500 From: Arnd Bergmann To: Scott Branden Cc: bcm-kernel-feedback-list@broadcom.com, Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Matt Mackall , Herbert Xu , Grant Likely , Ray Jui , Jonathan Richardson , Dmitry Torokhov , Anatol Pomazao , 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> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1424888184-22180-3-git-send-email-sbranden@broadcom.com> References: <1424888184-22180-3-git-send-email-sbranden@broadcom.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:o0MSYLdOo1KzgUi5rdzZR6PFYLzff54wrmExxCUNYwXqTlcJduh cgjUgkP+gSAoxja+U8PjP6FGzjv5aLzVpFh1FtoAZK2mC+KObbdf8QTwcXdkkDweDkZd8jp yoaxXiU73ABCK2l6J0uxurpQb9DeyPw9IXD6vfSh8dTeuST39wztUdyCCTqxl3oH9C6waUj vMVosqT2eDb/+HS4kLHUQ== X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1202 Lines: 38 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 > Signed-off-by: Scott Branden 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/