From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753233AbbJSJPu (ORCPT ); Mon, 19 Oct 2015 05:15:50 -0400 Received: from mx2.suse.de ([195.135.220.15]:58583 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750904AbbJSJPt (ORCPT ); Mon, 19 Oct 2015 05:15:49 -0400 Message-ID: <1445246052.1796.5.camel@suse.com> Subject: Re: [PATCH] USB: serial: cp210x: Workaround for cp2108 failure due to GET_LINE_CTL bug From: Oliver Neukum To: Konstantin Shkolnyy Cc: johan@kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 19 Oct 2015 11:14:12 +0200 In-Reply-To: <1444946786-18146-1-git-send-email-konstantin.shkolnyy@gmail.com> References: <1444946786-18146-1-git-send-email-konstantin.shkolnyy@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2015-10-15 at 17:06 -0500, Konstantin Shkolnyy wrote: > 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. Just a remark. > > @@ -865,18 +888,53 @@ static void cp210x_break_ctl(struct tty_struct *tty, int break_state) > > static int cp210x_startup(struct usb_serial *serial) > { > + struct usb_serial_port *port; > struct usb_host_interface *cur_altsetting; > struct cp210x_serial_private *spriv; > + unsigned int line_ctl; > + int err; > + > + /* We always expect a single port only */ > + if (serial->num_ports != 1) { > + dev_err(&serial->dev->dev, "%s - expected 1 port, found %d\n", > + __func__, serial->num_ports); > + return -EINVAL; > + } Why do you introduce this new check? It has no obvious connect with the subject of this fix. Regards Oliver