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=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 C6419C352A4 for ; Mon, 10 Feb 2020 09:35:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F905214DB for ; Mon, 10 Feb 2020 09:35:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581327306; bh=CubLCxy5uzdFRLVBYxa4/wTQ80OeP5mmUQWQQyBbjEY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=CBwIGKCtZ4g5EMX9TixLPVFehBok3pjpcUyC/l//c9I39z/BFK9+9icFSpEetRNSi f0HSB+zOenoZYTLz8j2FvluV2LLAkvlY8wWqudDR4osOW4RRwnDjCFpq0pHi2nix9Q tCpH5CWB1d1bn/xvgp4Rd7rLliIt4QlVUTss9P4E= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727029AbgBJJfF (ORCPT ); Mon, 10 Feb 2020 04:35:05 -0500 Received: from mail-lj1-f194.google.com ([209.85.208.194]:42582 "EHLO mail-lj1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726796AbgBJJfF (ORCPT ); Mon, 10 Feb 2020 04:35:05 -0500 Received: by mail-lj1-f194.google.com with SMTP id d10so6301087ljl.9; Mon, 10 Feb 2020 01:35:03 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=2dMtmeDRnp4IqIYHT+2e2+AiEKEG+n4IbCtoKAc5Vi0=; b=YMSk8Ba68rYzrYiuDUSRTkVrcxSAzMpeePY9x9yPBGYxQgeqakpvQSSKhjCslh0c5G Y3QiLFp93kbbrm0SmlYUPdn9BsMlgaOPdO1yzX29KFx8OuVcejNWfor605TBWot9EVTH Z0Cr9HuOfq42VJ5xEgNT5yt2t8jEJbfZw5kI+xieaDHNPSdSNhM+e5See4pvDw37C6j5 fk2xcChRfnSeyfOrifHAlErFR9RT61WsSUaljdGCIfp1N07nGsuO2iBlGF8IHHX5+NGC mmMeuuEoBRjpAhiSnGiugYEZddgpC/MB2fmfv74nap9NzpJt9dJpG8Ku6NDgsLL9oo1r Bfng== X-Gm-Message-State: APjAAAXTLuiFy+Ig8ORiQJ8LKVJNU/ntTmSs9WMmwh2LkH+Kb9eaSq3y vi33BN8gtZ6xtnOGP1XbJZA= X-Google-Smtp-Source: APXvYqxKy4brjEUxzjMG+gW2v+H+fGRjyDf1ySMlmY1e+JOpQOVWfLrGV9FmXnjkf5WDmP3pAYjLzg== X-Received: by 2002:a2e:5357:: with SMTP id t23mr302326ljd.227.1581327303258; Mon, 10 Feb 2020 01:35:03 -0800 (PST) Received: from xi.terra (c-12aae455.07-184-6d6c6d4.bbcust.telenor.se. [85.228.170.18]) by smtp.gmail.com with ESMTPSA id 5sm6000098lju.69.2020.02.10.01.35.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Feb 2020 01:35:02 -0800 (PST) Received: from johan by xi.terra with local (Exim 4.92.3) (envelope-from ) id 1j15T2-00045d-7f; Mon, 10 Feb 2020 10:35:00 +0100 Date: Mon, 10 Feb 2020 10:35:00 +0100 From: Johan Hovold To: Greg KH Cc: Johan Hovold , Jakub Nantl , Jonathan Olds , Michael Dreher , linux-usb@vger.kernel.org, stable Subject: Re: [PATCH] USB: serial: ch341: fix receiver regression Message-ID: <20200210093500.GA3539@localhost> References: <20200206111819.20829-1-johan@kernel.org> <20200206114546.GA3275679@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200206114546.GA3275679@kroah.com> Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Thu, Feb 06, 2020 at 11:45:46AM +0000, Greg Kroah-Hartman wrote: > On Thu, Feb 06, 2020 at 12:18:19PM +0100, Johan Hovold wrote: > > While assumed not to make a difference, not using the factor 2 prescaler > > makes the receiver more susceptible to errors. > > > > Specifically, there have been reports of problems with devices that > > cannot generate a 115200 rate with a smaller error than 2.1% (e.g. > > 117647 bps). But this can also be reproduced with a low-speed RS232 > > tranceiver at 115200 when the input rate is close to nominal. > > > > So whenever possible, enable the factor 2 prescaler and halve the > > divisor in order to use settings closer to that of the previous > > algorithm. > > > > Fixes: 35714565089e ("USB: serial: ch341: reimplement line-speed handling") > > Cc: stable # 5.5 > > Reported-by: Jakub Nantl > > Tested-by: Jakub Nantl > > Signed-off-by: Johan Hovold > > Reviewed-by: Greg Kroah-Hartman Thanks for reviewing. Now applied. Johan