Date: Wed, 7 Oct 2009 12:07:56 +0200
From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= 
	<u.kleine-koenig@pengutronix.de>
To: linux-kernel@vger.kernel.org
Cc: Russell King <rmk@arm.linux.org.uk>, Thomas Gleixner <tglx@linutronix.de>,
       linux-rt-users@vger.kernel.org, Sascha Hauer <s.hauer@pengutronix.de>
Subject: Using set_irq_handler in set_irq_type callback?
Message-ID: <20091007100756.GA5478@pengutronix.de>
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Hallo,

I'm seeing an imx31 (ARCH=arm) based system failing to boot .31.2-rt13.

The reason is that the irq for the ethernet device is level triggered,
but the handler for that interrupt is handle_edge_irq.
As the handler is threaded with PREEMPT_RT=y, the irq is only acked but
neither masked (as it is believed to be an edge irq) nor handled.  This
stucks the machine as the irq is still active.

I think the fix for that is adding something like:

	if (type & IRQ_TYPE_EDGE_BOTH)
		set_irq_handler(irq, handle_edge_irq);
	else
		set_irq_handler(irq, handle_level_irq);

to the chip's .set_type callback.  (Doing this directly fails, as
.set_type holds desc->lock which set_irq_handler acquires, too.  So
maybe I need to code up a handler that checks how a given irq triggers
and then calls handle_edge_irq or handle_level_irq.)

The thing that let's me question that change is that I only found[1] a
single .set_type callback that does something like that (i.e.
arch/blackfin/mach-common/ints-priority.c).

Do I just miss something or are there more than one platforms that are
in the need of handling this issue, too?

Best regards
Uwe

[1] checking files found by 

	git grep -c set_irq_handler | awk -F: '$2 >= 2'

-- 
Pengutronix e.K.                              | Uwe Kleine-K?nig            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |
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