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

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Message-Id: <200906230054.59669.rjw@sisk.pl>
Date:	Tue, 23 Jun 2009 00:54:59 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Kevin Hilman <khilman@...prootsystems.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] genirq: do not disable IRQ_WAKEUP marked irqs on suspend

On Friday 12 June 2009, Thomas Gleixner wrote:
> 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.

Agreed, but can you please suggest what way would be the best?

> 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.
>    ^^^^^^^^^^^^^^^^^^^^^^^^^^

Yes, it is, sorry for that.  I'll prepare a fix.

Best,
Rafael
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