linux-kernel - Re: [PATCH LINUX v3 09/10] tty: xuartps: Only handle RX IRQs when RX is enabled

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Message-ID: <20151205221912.GP4900@xsjsorenbubuntu>
Date:	Sat, 5 Dec 2015 14:19:12 -0800
From:	Sören Brinkmann <soren.brinkmann@...inx.com>
To:	Peter Hurley <peter@...leysoftware.com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>,
	Michal Simek <michal.simek@...inx.com>,
	<linux-kernel@...r.kernel.org>, <linux-serial@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH LINUX v3 09/10] tty: xuartps: Only handle RX IRQs when RX
 is enabled

On Sat, 2015-12-05 at 12:43PM -0500, Peter Hurley wrote:
> On 11/21/2015 09:59 PM, Soren Brinkmann wrote:
> > Ignore RX-related interrupts if RX is not enabled.
> 
> This doesn't look like a safe approach; fast-forward a couple of years and
> some is trying to add some feature but can't figure out why no data is
> arriving...
> 
> What is this trying to solve?

I definitely saw two kinds of lock ups. One was on the TX side, that the
system tried to print with the transmitter disabled.

The other on the RX side. I don't recall the details, but the system was
stuck in some RX-related function waiting for data while the receiver
was disabled. I think my explanation was that some IRQ condition becomes
true and is dispatched to the RX handler even though the receiver isn't
enabled.
I guess a better way for solving this would be to disable the IRQs that
call the RX handler when the receiver is disabled.

	Sören
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