Re: Reworking suspend-resume sequence (was: Re: PCI PM: Restore standard config registers of all devices early)

[Linus Torvalds <torvalds@linux-foundation.org>]

On Tue, 3 Feb 2009, Rafael J. Wysocki wrote:
>
> Having reconsidered it, I think that the "loop of disable_irq()" may be
> problematic due to MSI/MSI-X and devices that are put into D3 during the
> "normal" suspend.  That is, we shouldn't try to mask MSI/MSI-X for devices in
> D3

Rafael, you seem to be confused about what "disable_irq()" does.

It does not touch the driver hardware AT ALL. It literally just touches 
the interrupt controller, and even that only indirectly.

What disable_irq() does it literally:

	void disable_irq_nosync(unsigned int irq)
	{
	        struct irq_desc *desc = irq_to_desc(irq);
	        unsigned long flags;
  
	        if (!desc)
	                return;

	        spin_lock_irqsave(&desc->lock, flags);
	        if (!desc->depth++) {
	                desc->status |= IRQ_DISABLED;
	                desc->chip->disable(irq);
	        }
	        spin_unlock_irqrestore(&desc->lock, flags);
	}

and then it does a "synchronize_irq()" to wait to make sure that there are 
no pending ones.

And in many cases, even the

	desc->chip->disable(irq);

doesn't actually _do_ anything - we'll quite possibly continue to take the 
interrupt, and only when the interrupt happens will it see the "oh, 
IRQ_DISABLED is set" thing, and do something about it.

So don't worry about putting devices in D3 - disable_irq() will not care 
AT ALL whether the device is alive or not, and will never try to touch it 
anyway.

		Linus