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

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Date:	Fri, 12 Sep 2014 12:28:16 +0200
From:	Frans Klaver <frans.klaver@...ns.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
CC:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Peter Hurley <peter@...leysoftware.com>, <tony@...mide.com>,
	<gregkh@...uxfoundation.org>, <linux-kernel@...r.kernel.org>,
	<balbi@...com>, <linux-serial@...r.kernel.org>,
	<linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Alan Cox <alan@...ux.intel.com>
Subject: Re: [PATCH 09/16] tty: serial: 8250_dma: Add a TX trigger workaround
 for AM33xx

On Fri, Sep 12, 2014 at 11:51:22AM +0200, Sebastian Andrzej Siewior wrote:
> On 09/12/2014 11:40 AM, Frans Klaver wrote:
> 
> > I'm not sure. I just reproduced this on a boneblack, using your uart_v9
> > branch.
> > 
> >> This problem only pops-up if you use DMA. With disabled DMA you don't
> >> see this, right?
> > 
> > I get the lockup both with and without DMA enabled. Here's the 8250
> > config I use. Our full .config is attached in case it may provide
> > something relevant.
> 
> Hmm. I have a bone black here. Can you tell what you did to get this
> lockup? The port configuration (unless 115200 8N1) and what you did to
> get this lockup.

port config is 115200 8N1. I don't recall doing anything special. I
boot, login, less file and get a lock.


> > Something that may also help: when I have a lockup on the boneblack, dma
> > is enabled and something is written to console like I described earlier,
> > I get the following bad irq:
> 
> > Full dmesg is also attached.
> 
> This one should be stuffed by this:
> 	"[RFC] ARM: edma: unconditionally ack the error interrupt"
> 	https://lkml.org/lkml/2014/9/10/714

OK, that makes the console usable again after I write something to kmsg.

> > Hope you find something useful in there.
> 
> > Thanks,
> > Frans
> 
> Sebastian
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