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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 51E88C433DF for ; Fri, 15 May 2020 15:05:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 37F0C2078C for ; Fri, 15 May 2020 15:05:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726240AbgEOPFq (ORCPT ); Fri, 15 May 2020 11:05:46 -0400 Received: from mga05.intel.com ([192.55.52.43]:28339 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726140AbgEOPFq (ORCPT ); Fri, 15 May 2020 11:05:46 -0400 IronPort-SDR: MHM+E/F2RjRegcbJ5yG++1J3qOtHcitfn+3Cs17Ip0MdAmtUHM2T4JlsXFXVbLI3+ZgxpZ3Qvx X0fKuLp8sU/w== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 May 2020 08:05:45 -0700 IronPort-SDR: EX+/kA0HXNH84sqyToqDVeH2rEi9LIuOqiQ6K0oN24pfAe2f1Rat9eUkw4gWcL3iD9ayQ886Np VcYqaY6I9WsQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,395,1583222400"; d="scan'208";a="252057189" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by orsmga007.jf.intel.com with ESMTP; 15 May 2020 08:05:40 -0700 Received: from andy by smile with local (Exim 4.93) (envelope-from ) id 1jZbuA-006tTf-Vz; Fri, 15 May 2020 18:05:42 +0300 Date: Fri, 15 May 2020 18:05:42 +0300 From: Andy Shevchenko To: Serge Semin Cc: Serge Semin , Thomas Bogendoerfer , Greg Kroah-Hartman , Jiri Slaby , Alexey Malahov , Paul Burton , Ralf Baechle , Arnd Bergmann , Long Cheng , Maxime Ripard , Catalin Marinas , Will Deacon , Russell King , linux-mips@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, Heikki Krogerus , Kefeng Wang , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/4] serial: 8250_dw: Simplify the ref clock rate setting procedure Message-ID: <20200515150542.GN1634618@smile.fi.intel.com> References: <20200323024611.16039-1-Sergey.Semin@baikalelectronics.ru> <20200506233136.11842-1-Sergey.Semin@baikalelectronics.ru> <20200506233136.11842-4-Sergey.Semin@baikalelectronics.ru> <20200515140547.GE1634618@smile.fi.intel.com> <20200515145007.xjrx5mminxrh374d@mobilestation> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200515145007.xjrx5mminxrh374d@mobilestation> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Fri, May 15, 2020 at 05:50:07PM +0300, Serge Semin wrote: > On Fri, May 15, 2020 at 05:05:47PM +0300, Andy Shevchenko wrote: > > On Thu, May 07, 2020 at 02:31:34AM +0300, Serge Semin wrote: > > > Really instead of twice checking the clk_round_rate() return value > > > we could do it once, and if it isn't error the clock rate can be changed. > > > By doing so we decrease a number of ret-value tests and remove a weird > > > goto-based construction implemented in the dw8250_set_termios() method. > > > > > rate = clk_round_rate(d->clk, baud * 16); > > > - if (rate < 0) > > > - ret = rate; > > > > > - else if (rate == 0) > > > - ret = -ENOENT; > > > > This case now handled differently. > > I don't think it's good idea to change semantics. > > > > So, I don't see how this, after leaving the rate==0 case, would be better than > > original one. > > Semantic doesn't change. The code does exactly the same as before. If it didn't > I either would have provided a comment about this or just didn't introduce the > change in the first place. I guess you just don't see the whole picture of the > method. Take a look in the code. The ret variable's been used to skip the > "p->uartclk = rate" assignment. That's it. So the (rate == 0) will still be > considered as error condition, which causes the clock rate left unchanged. > Here is the code diff so you wouldn't need to dive deep into the driver > sources: > > < clk_disable_unprepare(d->clk); > < rate = clk_round_rate(d->clk, baud * 16); > < if (rate < 0) > < ret = rate; > < else if (rate == 0) > < ret = -ENOENT; > < else > < ret = clk_set_rate(d->clk, rate); > < clk_prepare_enable(d->clk); > < > < if (ret) > < goto out; > < > < p->uartclk = rate; > < > --- > > clk_disable_unprepare(d->clk); > > rate = clk_round_rate(d->clk, baud * 16); > > if (rate > 0) { > > ret = clk_set_rate(d->clk, rate); > > if (!ret) > > p->uartclk = rate; > > } > > clk_prepare_enable(d->clk); Thanks. Indeed, in the above it looks clear. -- With Best Regards, Andy Shevchenko