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=-3.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 06244C43387 for ; Thu, 17 Jan 2019 17:21:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B532020856 for ; Thu, 17 Jan 2019 17:21:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="SbEGfWea" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728001AbfAQRVM (ORCPT ); Thu, 17 Jan 2019 12:21:12 -0500 Received: from mail-pf1-f195.google.com ([209.85.210.195]:40631 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727854AbfAQRVM (ORCPT ); Thu, 17 Jan 2019 12:21:12 -0500 Received: by mail-pf1-f195.google.com with SMTP id i12so5132647pfo.7 for ; Thu, 17 Jan 2019 09:21:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=Pj6X9tOOCfkZoM+MJ1COk9HYEyQOdqx584QyCZWE8RU=; b=SbEGfWea6iltjztfTZBjLMBQ+c23sFpW5670JQ/EVn2kFcQd9BI8ivAY1qySo4TnpQ e9aYO9bqBqHid8iROVr0EdJtSO1a3GPq0DdXsfEXM2ubag2oBQ9xtHPVNKy2Xp+9hom0 TngvoHUqNOqITZccmUx4+4d/K2VJEIgFLerkc= 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:user-agent; bh=Pj6X9tOOCfkZoM+MJ1COk9HYEyQOdqx584QyCZWE8RU=; b=W/c0cVYodI2mOt8544fA3gL/BfN0zSCKXQ1E08fsh/MzKl4VczKCN3WhMcIvcyouk/ 51JH7vruQJaxYfsPuWJrRCILfsipzJuGqwxzBrUcUAhbKjlvLWrwv3vZVPwW3IrQjTSj x/dGOYFzi/Ws79iy/RVlPNN3TyHJ438aFvYL1v+Kqg09ztlU8OjzvAQ87Ohud29pRyxZ FbhUsGvnJwzzGKLF83VxeT4FlKEAFEkHkQSv8P3zpwvE8H93DLPueFSLPoefmPMUpWKA 3qB5Ps9xsDmv+eJYLnvzqjSBlwCmJOV+rmYDxzi4Tqr0A7TQ7Ew7b10KCnD6mNgPHEoW Df9w== X-Gm-Message-State: AJcUukfQ/1Dog+cKoIENRfh5EVy7O91/2yQjBn3twY983f0v3zez8UAN +QI94KXmF6T/M307JTdGDgLZkY+HpgR+1w== X-Google-Smtp-Source: ALg8bN5P8QVIOYmP6eHNM0LktEbHISHst/wN7hjWOC9iXUAUPVlWhPAL+pbynnhfXBkL4wqdHMYTLg== X-Received: by 2002:a65:4683:: with SMTP id h3mr13596063pgr.225.1547745671437; Thu, 17 Jan 2019 09:21:11 -0800 (PST) Received: from localhost ([2620:15c:202:1:75a:3f6e:21d:9374]) by smtp.gmail.com with ESMTPSA id a4sm2444740pgv.70.2019.01.17.09.21.10 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 17 Jan 2019 09:21:10 -0800 (PST) Date: Thu, 17 Jan 2019 09:21:09 -0800 From: Matthias Kaehlcke To: Johan Hovold Cc: Balakrishna Godavarthi , marcel@holtmann.org, johan.hedberg@gmail.com, linux-kernel@vger.kernel.org, linux-bluetooth@vger.kernel.org, hemantg@codeaurora.org, linux-arm-msm@vger.kernel.org, Johan Hovold Subject: Re: [PATCH v5 2/5] Bluetooth: hci_qca: Deassert RTS while baudrate change command Message-ID: <20190117172109.GU261387@google.com> References: <20190109145224.GN14782@localhost> <20190110143928.GE3430@localhost> <61301df80bd6a8ee0265b31b7f6a3aa1@codeaurora.org> <20190111013707.GD261387@google.com> <194b5d18ea86830b6a24939d483a964c@codeaurora.org> <20190111235633.GK261387@google.com> <20190115234628.GQ261387@google.com> <20190117160944.GV3691@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190117160944.GV3691@localhost> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-bluetooth-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org On Thu, Jan 17, 2019 at 05:09:44PM +0100, Johan Hovold wrote: > On Tue, Jan 15, 2019 at 03:46:28PM -0800, Matthias Kaehlcke wrote: > > > Using RTS seems|ed like a nice solutions, since it's the native way to > > prevent the controller from sending data, instead of doing some custom > > hack. However Johan seems to be fairly convinced that flow control and > > manual toggling of RTS can be problematic, and we have seen that > > disabling flow control has its own problems. Maybe it's time to > > consider other solutions like the DISCARD_RX flag we discussed > > earlier. Not that I really liked this custom solution, but in the end > > it might be a more robust way to address the issue. > > > > Johan/Marcel/others: Do you have any further ideas or input on this? > > I don't see why deasserting RTS wouldn't work, well at least as long as > the RTS signal is wired correctly. > > My point was simply that calling serdev_device_set_rts() will generally > not work unless you first disable automatic (i.e. hw-managed) flow > control using serdev_device_set_flow_control(). The exact behaviour is > serial-controller dependent, but I assume the driver needs to be > platform agnostic. I observed that the qcom_geni_serial driver doesn't raise RTS with flow control disabled. It seems we have to investigate why that's the case. I agree that the driver should be platform agnostic. Cheers Matthias