linux-kernel - Re: [PATCH v2] USB: serial: cp210x: Workaround for cp2108 failure due to GET_LINE

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Message-ID: <20151016154058.GB32032@localhost>
Date:	Fri, 16 Oct 2015 17:40:58 +0200
From:	Johan Hovold <johan@...nel.org>
To:	Konstantin Shkolnyy <konstantin.shkolnyy@...il.com>
Cc:	Johan Hovold <johan@...nel.org>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] USB: serial: cp210x: Workaround for cp2108 failure
 due to GET_LINE_CTL bug

On Fri, Oct 16, 2015 at 10:39:13AM -0500, Konstantin Shkolnyy wrote:
> On Fri, Oct 16, 2015 at 10:27 AM, Johan Hovold <johan@...nel.org> wrote:
> > On Fri, Oct 16, 2015 at 10:11:12AM -0500, Konstantin Shkolnyy wrote:
> >> On Fri, Oct 16, 2015 at 8:27 AM, Johan Hovold <johan@...nel.org> wrote:
> >> > On Thu, Oct 15, 2015 at 06:23:31PM -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.
> >> >
> >> > That sounds weird. Are you saying that all or only some cp2108 devices
> >> > would be affected by this? And only for the line-control register?
> >>
> >> The bug exists in all current cp2108 devices and affects only
> >> GET_LINE_CTL. But it may be fixed in a future revision.
> >
> > Ok, have you some kind of confirmation from silabs on this already?
> 
> I work for SiLabs.

Heh. :)

Johan
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