linux-kernel - Re: [PATCH] genirq: do not disable IRQ

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Date:	Fri, 12 Jun 2009 21:52:46 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Kevin Hilman <khilman@...prootsystems.com>
cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] genirq: do not disable IRQ_WAKEUP marked irqs on
 suspend

On Fri, 12 Jun 2009, Kevin Hilman wrote:
>   http://lkml.org/lkml/2009/5/4/448
> 
> Only difference is I did the checking outside of the lock, which is
> probably wrong.  In any case, you'll be interested in the thread that
> follows.

Hmm, darn. That means that on hardware which has trouble with the
delayed disable and therefor uses it's own chip->disable_irq() method
the suspend logic is wreckaged.

But there is always a way to get broken hardware tamed. :)

suspend does:
	__disable_irq();
		status |= IRQ_SUSPENDED;
		chip->disable_irq();

resume does:
       __enable_irq();
		status &= ~IRQ_SUSPENDED;
		chip->enable_irq();

So

-      set_irq_handler(handle_level_irq);
+      set_irq_handler(my_own_handler);

+my_own_handler()
+{
+	if (!(status & IRQ_SUSPENDED)) {
+	       handle_level_irq();
+	} else {
+	       mask_at_hardware_level();
+	       status |= IRQ_PENDING;
+	       save_important_information();
+	} 
+}

my_disable_irq()
{
+	if (!(status & IRQ_SUSPENDED))
	       mask_at_hardware_level();
}

my_enable_irq()
{
+	if (important_information_has_been_saved)
+	       replay_what_happened();
+
        unmask_at_hardware_level();
}

Ugly, but that might work somehow. Not sure about the replay part, but
that can be deferred via some more hackery as well :)

Raphael, these delayed disable and the chip->irq_disable() override
implications vs. suspend really need to be documented. The current
comment of suspend_device_irqs() is bogus:

 * During system-wide suspend or hibernation device interrupts need to be
 * disabled at the chip level and this function is provided for this purpose.
   ^^^^^^^^^^^^^^^^^^^^^^^^^^

Thanks,

	tglx
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