From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00852ECDE42 for ; Thu, 18 Oct 2018 03:12:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A1D9021480 for ; Thu, 18 Oct 2018 03:12:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A1D9021480 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-sky.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727364AbeJRLKF (ORCPT ); Thu, 18 Oct 2018 07:10:05 -0400 Received: from smtp2200-217.mail.aliyun.com ([121.197.200.217]:56324 "EHLO smtp2200-217.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727280AbeJRLKF (ORCPT ); Thu, 18 Oct 2018 07:10:05 -0400 X-Alimail-AntiSpam: AC=CONTINUE;BC=0.07727201|-1;CH=green;FP=0|0|0|0|0|-1|-1|-1;HT=e02c03295;MF=ren_guo@c-sky.com;NM=1;PH=DS;RN=18;RT=18;SR=0;TI=SMTPD_---.D3jfmVO_1539832245; Received: from localhost(mailfrom:ren_guo@c-sky.com fp:SMTPD_---.D3jfmVO_1539832245) by smtp.aliyun-inc.com(10.147.42.198); Thu, 18 Oct 2018 11:10:45 +0800 Date: Thu, 18 Oct 2018 11:10:24 +0800 From: Guo Ren To: Arnd Bergmann Cc: Andrew Morton , Daniel Lezcano , David Miller , gregkh , Christoph Hellwig , Marc Zyngier , Mark Rutland , Peter Zijlstra , Rob Herring , Thomas Gleixner , Linux Kernel Mailing List , linux-arch , DTML , Rob Herring , c-sky_gcc_upstream@c-sky.com, linfei_chen@c-sky.com, Mao Han Subject: Re: [PATCH V9 13/21] csky: Library functions Message-ID: <20181018031024.GA15088@guoren-Inspiron-7460> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 17, 2018 at 05:24:36PM +0200, Arnd Bergmann wrote: > On Tue, Oct 16, 2018 at 5:02 AM Guo Ren wrote: > > > +++ b/arch/csky/lib/delay.c > > @@ -0,0 +1,39 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd. > > +#include > > +#include > > +#include > > +#include > > + > > +void __delay(unsigned long loops) > > +{ > > + asm volatile ( > > + "mov r0, r0\n" > > + "1:declt %0\n" > > + "bf 1b" > > + : "=r"(loops) > > + : "0"(loops)); > > +} > > +EXPORT_SYMBOL(__delay); > > + > > +void __const_udelay(unsigned long xloops) > > +{ > > + unsigned long long loops; > > + > > + loops = (unsigned long long)xloops * loops_per_jiffy * HZ; > > + > > + __delay(loops >> 32); > > +} > > +EXPORT_SYMBOL(__const_udelay); > > I can't find any indication we discussed this part before. Can you > explain (in the > changelog and in a reply) if there is a reliable high-resolution clocksource > available in the architecture? If you can read the elapsed time here instead of > using the loops_per_jiffy estimate, that would make this more robust, as > well as speed up the boot. > > If you can't do that in general, that's fine, and you can add my I'll add TODO list here, __delay should use get_cycles() and we didn't implement __udelay() __ndelay() ... We'll improve it next. Best Regards Guo Ren