[PATCH 09/16] tty: serial: 8250_dma: Add a TX trigger workaround for AM33xx

Sebastian Andrzej Siewior bigeasy at linutronix.de
Fri Sep 12 00:23:24 PDT 2014

On 09/11/2014 07:04 PM, Frans Klaver wrote:
> On 11 September 2014 18:04:32 CEST, Sebastian Andrzej Siewior <bigeasy at linutronix.de> wrote:
>> On 09/11/2014 05:11 PM, Frans Klaver wrote:
>>> I can still reproduce it on am335x. I can get out of it as soon as
>>> something else gets written to the console though.
>>> # echo "<3>something" >/dev/kmsg
>> Is this to stall it or to get out of it?
> This is to get out of it. I do this from an ssh connection after the console got stuck. The 3 kind of ensures the message is actually sent to ttyS0.

Interesting. This shouldn't do anything. If there is a TX operation in
progress then ->start_tx() will simply return and the xmit buffer will
be send once the current TX operation completes.

Is there anything I can do to reproduce this behavior?
This problem only pops-up if you use DMA. With disabled DMA you don't
see this, right?


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