linux-kernel - Break doesn't work on a CP2105

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Message-ID: <ZEmDs0ASdnEAnpsL@minyard.net>
Date:   Wed, 26 Apr 2023 15:04:03 -0500
From:   Corey Minyard <minyard@....org>
To:     Craig Shelley <craig@...rotron.org.uk>,
        Johan Hovold <johan@...nel.org>
Cc:     Linux Kernel <linux-kernel@...r.kernel.org>,
        linux-usb@...r.kernel.org
Subject: Break doesn't work on a CP2105

I have a development board with a CP2105 on it, and I was trying to send
a break to it to do a sysrq.  And it wasn't working.

I have verified that the target driver works by setting a really slow
baud rate and sending something with a lot of zero bits.  It got breaks
just fine.

If I use TCSBRK, it seems to just send a short time with zeros, not
even a full character's worth.  It receives a valid character with the
top few bits set.  If I use TCSBRKP with a longer time, like 2.5
seconds, it waits the whole time, then at the very end it gets the
character as with the shorter break.

I can't find a programming manual for the chip, and I'm not sure what's
going on.

-corey