From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1754488AbbCIPFf (ORCPT <rfc822;w@1wt.eu>);
	Mon, 9 Mar 2015 11:05:35 -0400
Received: from mga14.intel.com ([192.55.52.115]:37530 "EHLO mga14.intel.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S932237AbbCIPF3 (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Mon, 9 Mar 2015 11:05:29 -0400
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.11,368,1422950400"; 
   d="scan'208";a="689220198"
Message-ID: <1425913502.3838.185.camel@linux.intel.com>
Subject: Re: [RFC] With 8250 Designware UART, if writes to the LCR failed
 the kernel will hung up
From: Alan Cox <alan@linux.intel.com>
To: Tim Kryger <tim.kryger@gmail.com>
Cc: "long.wanglong" <long.wanglong@huawei.com>,
        Peter Hurley <peter@hurleysoftware.com>,
        Zhang Zhen <zhenzhang.zhang@huawei.com>, linux-serial@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Tim Kryger <tim.kryger@linaro.org>, gregkh@linuxfoundation.org,
        Jamie Iles <jamie@jamieiles.com>, Arnd Bergmann <arnd@arndb.de>,
        shenjiangjiang@huawei.com, Wang Kai <morgan.wang@huawei.com>
Date: Mon, 09 Mar 2015 15:05:02 +0000
In-Reply-To: <CAD7vxxJvL61BjD9AMBF34Y8xnY+D-umuWLUq8Dh7ZbSm5tCE9w@mail.gmail.com>
References: <54F96F5B.2090601@huawei.com>
	 <54F9DACA.3020103@hurleysoftware.com>
	 <CAD7vxxJXEz8KfXd9fBjkxTi5Nnjyw0=wwvbw5qCSwCMbBd64eA@mail.gmail.com>
	 <54FD4779.3020902@huawei.com> <1425907939.3838.182.camel@linux.intel.com>
	 <CAD7vxxJvL61BjD9AMBF34Y8xnY+D-umuWLUq8Dh7ZbSm5tCE9w@mail.gmail.com>
Organization: Intel Corporation
Content-Type: text/plain; charset="UTF-8"
X-Mailer: Evolution 3.12.9 (3.12.9-1.fc21) 
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, 2015-03-09 at 07:36 -0700, Tim Kryger wrote:
> On Mon, Mar 9, 2015 at 6:32 AM, Alan Cox <alan@linux.intel.com> wrote:
> >> Maybe the next release of the board we will upgrade the serial block to the new version.
> >> but the issue is that how we circumvent this problem in kernel?
> >
> > What is the official vendor workaround ?
> 
> They introduced a UART_16550_COMPATIBLE option for the IP which should
> be selected.
> 
> If configured, writes to the LCR are allowed even if it is "busy" so
> there is no need to retry.
> 
> More importantly there is no possibility of failing to write the LCR
> after numerous retries.


Ah no - I meant what is their official software workaround for existing
parts with the bug ? Presumably they have an errata document that
discusses this and the correct methods they recommend to avoid the
hang ?

Alan