From: Greg KH <gregkh@linuxfoundation.org>
To: Johan Hovold <johan@kernel.org>
Cc: Jakub Nantl <jn@forever.cz>, Jonathan Olds <jontio@i4free.co.nz>,
Michael Dreher <michael@5dot1.de>,
linux-usb@vger.kernel.org, stable <stable@vger.kernel.org>
Subject: Re: [PATCH] USB: serial: ch341: fix receiver regression
Date: Thu, 6 Feb 2020 11:45:46 +0000 [thread overview]
Message-ID: <20200206114546.GA3275679@kroah.com> (raw)
In-Reply-To: <20200206111819.20829-1-johan@kernel.org>
On Thu, Feb 06, 2020 at 12:18:19PM +0100, Johan Hovold wrote:
> While assumed not to make a difference, not using the factor 2 prescaler
> makes the receiver more susceptible to errors.
>
> Specifically, there have been reports of problems with devices that
> cannot generate a 115200 rate with a smaller error than 2.1% (e.g.
> 117647 bps). But this can also be reproduced with a low-speed RS232
> tranceiver at 115200 when the input rate is close to nominal.
>
> So whenever possible, enable the factor 2 prescaler and halve the
> divisor in order to use settings closer to that of the previous
> algorithm.
>
> Fixes: 35714565089e ("USB: serial: ch341: reimplement line-speed handling")
> Cc: stable <stable@vger.kernel.org> # 5.5
> Reported-by: Jakub Nantl <jn@forever.cz>
> Tested-by: Jakub Nantl <jn@forever.cz>
> Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
next prev parent reply other threads:[~2020-02-06 11:45 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-06 11:18 [PATCH] USB: serial: ch341: fix receiver regression Johan Hovold
2020-02-06 11:45 ` Greg KH [this message]
2020-02-10 9:35 ` Johan Hovold
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