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_PASS,URIBL_BLOCKED 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 F3808C5CFEB for ; Wed, 11 Jul 2018 14:23:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BA24B20875 for ; Wed, 11 Jul 2018 14:23:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BA24B20875 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.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 S2388566AbeGKO1x (ORCPT ); Wed, 11 Jul 2018 10:27:53 -0400 Received: from mga11.intel.com ([192.55.52.93]:33885 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387949AbeGKO1x (ORCPT ); Wed, 11 Jul 2018 10:27:53 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Jul 2018 07:23:18 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,338,1526367600"; d="scan'208";a="73957147" Received: from smile.fi.intel.com (HELO smile) ([10.237.72.86]) by orsmga002.jf.intel.com with ESMTP; 11 Jul 2018 07:23:15 -0700 Message-ID: Subject: Re: [PATCH v4 3/3] serial: 8250_dw: add fractional divisor support From: Andy Shevchenko To: Jisheng Zhang Cc: Greg Kroah-Hartman , Jiri Slaby , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-serial@vger.kernel.org Date: Wed, 11 Jul 2018 17:23:13 +0300 In-Reply-To: <20180711144125.7d4e6a73@xhacker.debian> References: <20180710110942.5b0a016e@xhacker.debian> <20180710111516.13b8c570@xhacker.debian> <8c5b6bbbde12b0836e1f833c86b805a817596654.camel@linux.intel.com> <20180711144125.7d4e6a73@xhacker.debian> Organization: Intel Finland Oy Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.1-2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2018-07-11 at 14:41 +0800, Jisheng Zhang wrote: > On Tue, 10 Jul 2018 19:19:21 +0300 Andy Shevchenko wrote: > > > +/* > > > + * divisor = div(I) + div(F) > > > + * "I" means integer, "F" means fractional > > > + * quot = div(I) = clk / (16 * baud) > > > + * frac = div(F) * 2^dlf_size > > > + * > > > + * let rem = clk % (16 * baud) > > > + * we have: div(F) * (16 * baud) = rem > > > + * so frac = 2^dlf_size * rem / (16 * baud) = (rem << dlf_size) / > > > (16 > > > * baud) > > > + */ > > > + quot = p->uartclk / (16 * baud); > > > + rem = p->uartclk % (16 * baud); > > > + *frac = DIV_ROUND_CLOSEST(rem << d->dlf_size, 16 * baud > My python coding skill is limited. So I wrote a simple c program to > do the check for common clks and baudrate combination. All passed. I > paste the code here: > OK, I wrote test case in Python: https://gist.github.com/andy-shev/5e980f1d752617ba814725248556ac19 Looks good to me. Please, send v6 and assume my Reviewed-by for entire series. -- Andy Shevchenko Intel Finland Oy