From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965312AbbJ1Ivd (ORCPT ); Wed, 28 Oct 2015 04:51:33 -0400 Received: from mail-lb0-f177.google.com ([209.85.217.177]:36285 "EHLO mail-lb0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965239AbbJ1Iv1 (ORCPT ); Wed, 28 Oct 2015 04:51:27 -0400 Date: Wed, 28 Oct 2015 09:51:26 +0100 From: Johan Hovold To: Konstantin Shkolnyy Cc: johan@kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 3/3] USB: serial: cp210x: Workaround cp2108 GET_LINE_CTL bug Message-ID: <20151028085126.GA28572@localhost> References: <1445982814-11638-1-git-send-email-konstantin.shkolnyy@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1445982814-11638-1-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 Tue, Oct 27, 2015 at 04:53:34PM -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. > > Signed-off-by: Konstantin Shkolnyy > --- > drivers/usb/serial/cp210x.c | 70 ++++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 66 insertions(+), 4 deletions(-) > +/* > + * Must always be called instead of cp210x_get_config(CP210X_GET_LINE_CTL) > + * to workaround cp2108 bug and get correct value. > + */ > +static int cp210x_get_line_ctl(struct usb_serial_port *port, > + unsigned int *ctl) No need to break this line anymore. > +{ > + struct cp210x_port_private *port_priv = usb_get_serial_port_data(port); > + int err; > + > + err = cp210x_get_config(port, CP210X_GET_LINE_CTL, ctl, 2); > + if (err) > + return err; > + > + /* Workaround swapped bytes in 16-bit value from CP210X_GET_LINE_CTL */ > + if (port_priv->has_swapped_line_ctl) > + *ctl = swab16((u16)(*ctl)); > + > + return 0; > +} > @@ -883,6 +940,7 @@ static int cp210x_port_probe(struct usb_serial_port *port) > struct usb_serial *serial = port->serial; > struct usb_host_interface *cur_altsetting; > struct cp210x_port_private *port_priv; > + int err; > > port_priv = kzalloc(sizeof(*port_priv), GFP_KERNEL); > if (!port_priv) > @@ -893,6 +951,10 @@ static int cp210x_port_probe(struct usb_serial_port *port) > > usb_set_serial_port_data(port, port_priv); > > + err = cp210x_detect_swapped_line_ctl(port); > + if (err) > + kfree(port_priv); You forgot to return err here... > + > return 0; > } I gave the series a really quick test on an cp2102-device I had lying around. I assume you verified the changes on some other older devices as well? Fix the above, and I'll queue this up for 4.4-rc. Thanks, Johan