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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 3948BC282C0 for ; Wed, 23 Jan 2019 12:57:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 083B321848 for ; Wed, 23 Jan 2019 12:57:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="H5zBqLdq"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="Ddozk3S+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726367AbfAWM5p (ORCPT ); Wed, 23 Jan 2019 07:57:45 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:41756 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726029AbfAWM5p (ORCPT ); Wed, 23 Jan 2019 07:57:45 -0500 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 9769260736; Wed, 23 Jan 2019 12:57:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1548248263; bh=Mz+DueOzCHqjZ4WaYFUaDzBjJPzVrxhpr9P0YTWphvU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=H5zBqLdql9Dr5PmUYZy7+f552lAhtjCw+B7wCKmhvWXmqZOaVYqUZw+t3918bgVhn UtjG4Ywj8GuM+6J0AmYax95LAAx8WFpAFkKxw4qrhHIWlRHM8zZ8ayLixyVxhg5o8g YqbfnDj1FAUej60O6ZRo9wON36O7UnTr9m2ejnyE= Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.codeaurora.org (Postfix) with ESMTP id D0A0C6024C; Wed, 23 Jan 2019 12:57:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1548248262; bh=Mz+DueOzCHqjZ4WaYFUaDzBjJPzVrxhpr9P0YTWphvU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Ddozk3S+mXaTq+cf+U0u96VsBktf4zD8r6mxOun444IjsvpB+zplBbd88UXrqEgtb zvYkAdMoEeCYE3izRvlAiC+dAjoR2eU5M3ikGvLKS3kfvSfi6e5VChZ0njs5DLVcsL eOSrgqrG+6o5+jyuD/ybWmBeUd8ho9CC146JBe+Y= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Wed, 23 Jan 2019 18:27:42 +0530 From: Balakrishna Godavarthi To: Matthias Kaehlcke Cc: Johan Hovold , 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 In-Reply-To: <20190122215330.GI261387@google.com> References: <20190111013707.GD261387@google.com> <194b5d18ea86830b6a24939d483a964c@codeaurora.org> <20190111235633.GK261387@google.com> <20190115234628.GQ261387@google.com> <20190117160944.GV3691@localhost> <20190117172109.GU261387@google.com> <20190118094416.GB3691@localhost> <20190119003109.GD261387@google.com> <24831204bab89250099ca56e7562bd16@codeaurora.org> <20190122215330.GI261387@google.com> Message-ID: X-Sender: bgodavar@codeaurora.org User-Agent: Roundcube Webmail/1.2.5 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Matthias, On 2019-01-23 03:23, Matthias Kaehlcke wrote: > On Mon, Jan 21, 2019 at 08:11:39PM +0530, Balakrishna Godavarthi wrote: >> Hi Matthias, >> >> On 2019-01-19 06:01, Matthias Kaehlcke wrote: >> > On Fri, Jan 18, 2019 at 10:44:16AM +0100, Johan Hovold wrote: >> > > On Thu, Jan 17, 2019 at 09:21:09AM -0800, Matthias Kaehlcke wrote: >> > > >> > > > 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. >> > > >> > > Sounds like a driver bug, unless the hardware is just "odd". The >> > > driver implementation of this looks very non-standard judging from a >> > > quick peek. >> > > >> > > In fact, qcom_geni_serial_get_mctrl() is currently a no-op if hardware >> > > flow control is not enabled: >> > > >> > > if (uart_console(uport) || !uart_cts_enabled(uport)) >> > > return; >> > > >> > > Perhaps dropping the !uart_cts_enabled() test is sufficient. >> > >> > Thanks for taking a look Johan, that was indeed the problem (also >> > in set_mctrl()). I posted a fix: >> > https://lore.kernel.org/patchwork/patch/1033611/ >> > >> > Balakrishna, the following (applied on top of your patch) works for me >> > with the UART patch above: >> > >> >> [Bala]: will test and update BT patch accordingly. > > Note that Johan pointed out that hci_uart_set_flow_control() deasserts > RTS when flow control is disabled, so the _set_rts() calls can be > removed. With that only a single action needs to be undone in case of > an error, you can consider to keep the return instead of using the > goto introduced by my patch. > [Bala]: ok sure. will note this. > Please keep/adapt the "Deassert RTS while changing the baudrate ..." > comment to leave it clear to posterity why flow control is disabled > during baudrate changes. It's fairly obvious once you understand the > problem and that disabling flow control deasserts RTS, but it took us > a while to get there, initially we only had a comment saying > "disabling flow control is mandatory" (I recall I inquired about this > multiple times during the initial review of the wcn3990 patches ;-) > > Thanks > > Matthias -- Regards Balakrishna.