From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753846AbbJTHuH (ORCPT ); Tue, 20 Oct 2015 03:50:07 -0400 Received: from mail-lb0-f174.google.com ([209.85.217.174]:33831 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753634AbbJTHuE (ORCPT ); Tue, 20 Oct 2015 03:50:04 -0400 Date: Tue, 20 Oct 2015 09:50:06 +0200 From: Johan Hovold To: Konstantin Shkolnyy Cc: johan@kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] USB: serial: cp210x: Workaround for occasional cp2108 hangs. Message-ID: <20151020075006.GB20289@localhost> References: <1445292100-27946-1-git-send-email-konstantin.shkolnyy@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1445292100-27946-1-git-send-email-konstantin.shkolnyy@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 19, 2015 at 05:01:40PM -0500, Konstantin Shkolnyy wrote: > This patch can only be applied after the patch titled > "USB: serial: cp210x: Implement 16-bit register access functions" No need to put this in the commit message, ordering is assumed to be correct when you submit a series of patches. > Work around 2 cp2108 bugs: > > 1) cp2108 GET_LINE_CTL returns the 16-bit value with the 2 bytes swapped. > However, SET_LINE_CTL functions properly. When the driver tries to modify > the register, it reads it, modifies some bits and writes back. Because > the read bytes were swapped, this often results in an invalid value to be > written. In turn, this causes cp2108 respond with a stall. The stall > sometimes doesn't clear properly and cp2108 starts responding to following > valid commands also with stalls, effectively failing. > > 2) Occasionally, writing data and immediately closing the port makes cp2108 > stop responding. The device had to be unplugged to clear the error. > The failure is induced by shutting down the device while its Tx queue still > has unsent data. This condition is avoided by issuing PURGE command from > the close() callback. Two distinct fixes need to go in separate patches. You should end up with something like the following series - fix hang after close (purge) - refactor lcr handling - fix cp2108 lcr handling - more clean ups... Thanks, Johan