Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965580AbaFTIP5 (ORCPT ); Fri, 20 Jun 2014 04:15:57 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:42457 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934721AbaFTIPv (ORCPT ); Fri, 20 Jun 2014 04:15:51 -0400 Date: Fri, 20 Jun 2014 09:15:09 +0100 From: Will Deacon To: Tomasz Figa Cc: Doug Anderson , Amit Daniel Kachhap , linux-samsung-soc , Kukjin Kim , Daniel Lezcano , Thomas Gleixner , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , David Riley , Jonathan Austin Subject: Re: [PATCH v2] clocksource: exynos-mct: Register the timer for stable udelay Message-ID: <20140620081509.GA25104@arm.com> References: <1403167145-5267-1-git-send-email-amit.daniel@samsung.com> <53A2B9C3.1050906@gmail.com> <53A30D08.6070107@gmail.com> <53A31291.9000007@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53A31291.9000007@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 19, 2014 at 05:40:49PM +0100, Tomasz Figa wrote: > On 19.06.2014 18:31, Doug Anderson wrote: > >>> My personal vote would be to submit a patch to change "cycles_t" to > >>> always be 32-bits. Given that 32-bits was fine for udelay() for ARM > >>> that seems sane and simple. If someone later comes up with a super > >>> compelling reason why we need 64-bit timers for udelay (really??) then > >>> they can later add all the complexity needed. > >> > >> Yes, this could work. I'm not sure what else cycles_t is used for, though. > > > > True, it is a bit questionable to change this since it's a type that's > > not obviously just for udelay(). Perhaps a better option would be to > > make a new typedef for the result of read_current_timer(). ...or just > > change it to return a u32? > > > > Sounds good to me, but let's hear other opinions. I'm adding Will and > Jonathan as they wrote the ARM delay timer code. I think cycles_t is only used for small interval calculations at the moment, but I remember Ted mentioning something about using it (or something similar) as a source of early entropy, in which case the more bits the better. That said, I can't find any code in the tree to that effect. Will -- 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/