Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751502AbdFBWpb (ORCPT ); Fri, 2 Jun 2017 18:45:31 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:40862 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750971AbdFBWp2 (ORCPT ); Fri, 2 Jun 2017 18:45:28 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org C0CC660915 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=sboyd@codeaurora.org Date: Fri, 2 Jun 2017 15:45:26 -0700 From: Stephen Boyd To: Phil Elwell Cc: Michael Turquette , Eric Anholt , Stefan Wahren , Florian Fainelli , linux-clk@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/2] clk: bcm2835: Minimise clock jitter for PCM clock Message-ID: <20170602224526.GC20170@codeaurora.org> References: <9989244b-ca4d-9081-95d9-b24f51099222@raspberrypi.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9989244b-ca4d-9081-95d9-b24f51099222@raspberrypi.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 843 Lines: 22 On 06/01, Phil Elwell wrote: > Fractional clock dividers generate accurate average frequencies but > with jitter, particularly when the integer divisor is small. > > Introduce a new metric of clock accuracy to penalise clocks with a good > average but worse jitter compared to clocks with an average which is no > better but with lower jitter. The metric is the ideal rate minus the > worse deviation from that ideal using the nearest integer divisors. > > Use this metric for parent selection for clocks requiring low jitter > (currently just PCM). > > Signed-off-by: Phil Elwell > Reviewed-by: Eric Anholt > Acked-by: Stefan Wahren > --- Applied to clk-next -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project