Re: [PATCH] USB: serial: cp210x: Workaround for cp2108 failure due to GET_LINE_CTL bug

Path	csiph.com!goblin2!goblin.stu.neva.ru!aioe.org!bofh.it!news.nic.it!robomod
From	Oliver Neukum <oneukum@suse.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] USB: serial: cp210x: Workaround for cp2108 failure due to GET_LINE_CTL bug
Date	Mon, 19 Oct 2015 11:20:02 +0200
Message-ID	<qleLM-8ro-25@gated-at.bofh.it> (permalink)
References	<qjYSK-30t-7@gated-at.bofh.it>
X-Original-To	Konstantin Shkolnyy <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	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	40
Organization	linux.* mail to news gateway
X-Original-Cc	johan@kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
X-Original-Date	Mon, 19 Oct 2015 11:14:12 +0200
X-Original-Message-ID	<1445246052.1796.5.camel@suse.com>
X-Original-References	<1444946786-18146-1-git-send-email-konstantin.shkolnyy@gmail.com>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1250493

Show key headers only | View raw

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


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Thread

[PATCH] USB: serial: cp210x: Workaround for cp2108 failure due to GET_LINE_CTL bug Konstantin Shkolnyy <konstantin.shkolnyy@gmail.com> - 2015-10-16 00:10 +0200
  Re: [PATCH] USB: serial: cp210x: Workaround for cp2108 failure due  to GET_LINE_CTL bug Oliver Neukum <oneukum@suse.com> - 2015-10-19 11:20 +0200
    Re: [PATCH] USB: serial: cp210x: Workaround for cp2108 failure due to  GET_LINE_CTL bug Konstantin Shkolnyy <konstantin.shkolnyy@gmail.com> - 2015-10-19 15:30 +0200

csiph-web