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From: Peter Maydell <peter.maydell@linaro.org>
Date: Fri, 23 Mar 2018 11:07:38 +0000
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Subject: Re: [Qemu-devel] [PATCH] i.MX: Support serial RS-232 break properly
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To: Trent Piepho <tpiepho@impinj.com>
Cc: qemu-arm <qemu-arm@nongnu.org>, QEMU Developers <qemu-devel@nongnu.org>, Andrey Smirnov <andrew.smirnov@gmail.com>, Paolo Bonzini <pbonzini@redhat.com>, Peter Chubb <peter.chubb@nicta.com.au>

On 20 March 2018 at 01:36, Trent Piepho <tpiepho@impinj.com> wrote:
> Linux does not detect a break from this IMX serial driver as a magic
> sysrq.  Nor does it note a break in the port error counts.
>
> The former is because the Linux driver uses the BRCD bit in the USR2
> register to trigger the RS-232 break handler in the kernel, which is
> where sysrq hooks in.  The emulated UART was not setting this status
> bit.
>
> The latter is because the Linux driver expects, in addition to the BRK
> bit, that the ERR bit is set when a break is read in the FIFO.  A break
> should also count as a frame error, so add that bit too.
>
> Cc: Andrey Smirnov <andrew.smirnov@gmail.com>
> Signed-off-by: Trent Piepho <tpiepho@impinj.com>

Yep, the data sheet is nice and clear here about the requirements.

Applied to target-arm.next, thanks.

-- PMM