Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965728AbbFJQ1t (ORCPT ); Wed, 10 Jun 2015 12:27:49 -0400 Received: from ns.horizon.com ([71.41.210.147]:62087 "HELO ns.horizon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S965648AbbFJQ1k (ORCPT ); Wed, 10 Jun 2015 12:27:40 -0400 Date: 10 Jun 2015 12:27:38 -0400 Message-ID: <20150610162738.24160.qmail@ns.horizon.com> From: "George Spelvin" To: arjanvandeven@gmail.com, linux@horizon.com Subject: Re: Discussion: quick_pit_calibrate is slow Cc: a.p.zijlstra@chello.nl, adrian.hunter@intel.com, ak@linux.intel.com, akpm@linux-foundation.org, arjan@infradead.org, bp@alien8.de, hpa@zytor.com, linux-kernel@vger.kernel.org, luto@amacapital.net, mingo@kernel.org, penberg@iki.fi, tglx@linutronix.de, torvalds@linux-foundation.org In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 723 Lines: 15 Arjan van de Ven wrote: > btw one thing to think about; if you calibrate VERY quickly, you need > to consider spread spectrum clocking. Excellent point! But spread spectrum clock modulation rates are typically about 30 kHz, so 1 ms will average over 30 cycles, which should be enough. The faster the modulation rate, the more the EMI peak is flattened. But too fast produces unaceptable cycle-to-cycle timing variations, also known as clock jitter. -- 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/