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

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Message-ID: <CAL_jEz_jBW3eJ-Hsq6xKFx6Mi-Z32q9PJxYp5NnJxMkRVDx8-Q@mail.gmail.com>
Date:	Fri, 16 Oct 2015 10:39:13 -0500
From:	Konstantin Shkolnyy <konstantin.shkolnyy@...il.com>
To:	Johan Hovold <johan@...nel.org>
Cc:	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 10:27 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.

Thanks,
Konstantin
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