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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 3C643C34051 for ; Wed, 19 Feb 2020 14:38:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 140BA24654 for ; Wed, 19 Feb 2020 14:38:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="R1dPxReh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726667AbgBSOiU (ORCPT ); Wed, 19 Feb 2020 09:38:20 -0500 Received: from hqnvemgate26.nvidia.com ([216.228.121.65]:4860 "EHLO hqnvemgate26.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726539AbgBSOiT (ORCPT ); Wed, 19 Feb 2020 09:38:19 -0500 Received: from hqpgpgate102.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate26.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Wed, 19 Feb 2020 06:38:04 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate102.nvidia.com (PGP Universal service); Wed, 19 Feb 2020 06:38:18 -0800 X-PGP-Universal: processed; by hqpgpgate102.nvidia.com on Wed, 19 Feb 2020 06:38:18 -0800 Received: from [10.21.133.51] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 19 Feb 2020 14:38:14 +0000 Subject: Re: [PATCH for 5.6 v2] tty: serial: tegra: Handle RX transfer in PIO mode if DMA wasn't started To: Dmitry Osipenko , Jiri Slaby , "Laxman Dewangan" , Greg Kroah-Hartman , Thierry Reding CC: , , References: <20200209164415.9632-1-digetx@gmail.com> <15b01f79-007d-09bb-03be-050c009ceff6@suse.cz> <4d9a2352-6daa-4dcc-376b-175b1398ff6a@gmail.com> From: Jon Hunter Message-ID: <01397ba1-a738-257a-adb1-84cdcba68a57@nvidia.com> Date: Wed, 19 Feb 2020 14:38:12 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <4d9a2352-6daa-4dcc-376b-175b1398ff6a@gmail.com> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: quoted-printable DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1582123084; bh=w7DzjaP66efSnxdr3Cf/Q2kn+epuTGow7yByRK1aMQk=; h=X-PGP-Universal:Subject:To:CC:References:From:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=R1dPxRehYvhXI70N/7S5SupHF72Hin1MIdm5n3VGFBjuBvyEKSxqIdx2nqx4e3hge En3TC0gegHZDYz7HqNFrsvLIwgFnYNFZonoQ8NB3HAq0IRwd68hXy6L3LbIOH4nSB0 2zjFTQPUqHfGZdcKtZ0XyQfH3TrjhOzP0nNhq0a14oNCm2iCymFCNv5zQeVVd02FZI +T+zJu9E2tOUZPZFWfI26f7Us/jpBvK03rLKnOWSx92Xx7YI4f1BoA96UFiCpgxJU+ YLi7cOb+bT2+rqBxrbJJLoILF3gB3W8RhCsVXXGEzgQVrOZiPSu5hFmkktA+74rvWj cpcBjBrsAnZvQ== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/02/2020 12:25, Dmitry Osipenko wrote: > 17.02.2020 10:37, Jiri Slaby =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> On 09. 02. 20, 17:44, Dmitry Osipenko wrote: >>> It is possible to get an instant RX timeout or end-of-transfer interrup= t >>> before RX DMA was started, if transaction is less than 16 bytes. Transf= er >>> should be handled in PIO mode in this case because DMA can't handle it. >>> This patch brings back the original behaviour of the driver that was >>> changed by accident by a previous commit, it fixes occasional Bluetooth= HW >>> initialization failures which I started to notice recently. >>> >>> Fixes: d5e3fadb7012 ("tty: serial: tegra: Activate RX DMA transfer by r= equest") >>> Signed-off-by: Dmitry Osipenko >>> --- >>> >>> Changelog: >>> >>> v2: - Corrected commit's title by adding the accidentally missed "tegra= : " >>> to the prefix. >>> >>> drivers/tty/serial/serial-tegra.c | 35 ++++++++++++++----------------- >>> 1 file changed, 16 insertions(+), 19 deletions(-) >>> >>> diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/ser= ial-tegra.c >>> index 33034b852a51..8de8bac9c6c7 100644 >>> --- a/drivers/tty/serial/serial-tegra.c >>> +++ b/drivers/tty/serial/serial-tegra.c >>> @@ -692,11 +692,22 @@ static void tegra_uart_copy_rx_to_tty(struct tegr= a_uart_port *tup, >>> count, DMA_TO_DEVICE); >>> } >>> =20 >>> +static void do_handle_rx_pio(struct tegra_uart_port *tup) >>> +{ >>> + struct tty_struct *tty =3D tty_port_tty_get(&tup->uport.state->port); >>> + struct tty_port *port =3D &tup->uport.state->port; >>> + >>> + tegra_uart_handle_rx_pio(tup, port); >>> + if (tty) { >> >> What's the tty good for here, actually? >> >>> + tty_flip_buffer_push(port); >>> + tty_kref_put(tty); >>> + } >>> +} >=20 > I'm not really a TTY expert.. >=20 > Jon, maybe you have any clue whether TTY could disappear while port is > opened? Nothing specific that I am aware of. The function tty_kref_get() appears to check that the tty pointer is valid and so it would seem logical to check here as well. But happy to be corrected :-) Jon --=20 nvpublic