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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6FF60C433EF for ; Tue, 19 Apr 2022 07:29:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349375AbiDSHcK (ORCPT ); Tue, 19 Apr 2022 03:32:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53390 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236225AbiDSHcJ (ORCPT ); Tue, 19 Apr 2022 03:32:09 -0400 Received: from mail-sh.amlogic.com (mail-sh.amlogic.com [58.32.228.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4A7A332990; Tue, 19 Apr 2022 00:29:27 -0700 (PDT) Received: from [10.18.29.47] (10.18.29.47) by mail-sh.amlogic.com (10.18.11.5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.14; Tue, 19 Apr 2022 15:29:20 +0800 Message-ID: Date: Tue, 19 Apr 2022 15:29:19 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH V2 1/2] tty: serial: meson: Add a 12MHz internal clock rate to calculate baud rate in order to meet the baud rate requirements of special BT modules Content-Language: en-US To: Andy Shevchenko CC: "open list:SERIAL DRIVERS" , linux-arm Mailing List , linux-amlogic , Linux Kernel Mailing List , Greg Kroah-Hartman , Neil Armstrong , Kevin Hilman , Jerome Brunet , Jiri Slaby , Martin Blumenstingl References: <20220418053202.24528-1-yu.tu@amlogic.com> <20220418053202.24528-2-yu.tu@amlogic.com> From: Yu Tu In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.18.29.47] X-ClientProxiedBy: mail-sh.amlogic.com (10.18.11.5) To mail-sh.amlogic.com (10.18.11.5) Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Hi Andy, Thank you for your advice. On 2022/4/18 20:09, Andy Shevchenko wrote: > [ EXTERNAL EMAIL ] > > On Mon, Apr 18, 2022 at 8:50 AM Yu Tu wrote: >> >> A /2 divider over XTAL was introduced since G12A, and is preferred >> to be used over the still present /3 divider since it provides much >> closer frequencies vs the request baudrate.Especially the BT module > > 'e. E' (mind the space) My statement is a whole. There should be no spaces. > >> uses 3Mhz baud rate. 8Mhz calculations can lead to baud rate bias, >> causing some problems. > > ... > >> +struct meson_uart_data { >> + bool has_xtal_div2; > > I would prefer to see this as an unsigned int and with a less > particular name, e.g. xtal_div would suffice. I don't have a problem with your suggestion.Let's see What Neil has to say. > >> +}; > > ... > >> + unsigned int xtal_div = 3; > >> + if (private_data && private_data->has_xtal_div2) { >> + xtal_div = 2; > > Better to define privata data always > > >> + val |= AML_UART_BAUD_XTAL_DIV2; >> + } >> + val |= DIV_ROUND_CLOSEST(port->uartclk / xtal_div, baud) - 1; > >