linux-kernel - Re: pci_set_power_state() failure and breaking suspend

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Message-Id: <200610241400.06047.rjw@sisk.pl>
Date:	Tue, 24 Oct 2006 14:00:04 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	linux1394-devel@...ts.sourceforge.net,
	linuxppc-dev list <linuxppc-dev@...abs.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Greg KH <greg@...ah.com>, Pavel Machek <pavel@....cz>
Subject: Re: pci_set_power_state() failure and breaking suspend

On Tuesday, 24 October 2006 08:54, Benjamin Herrenschmidt wrote:
> So I noticed a small regression that I think might uncover a deeper
> issue...
> 
> Recently, ohci1394 grew some "proper" error handling in its suspend
> function, something that looks like:
> 
>         err = pci_set_power_state(pdev, pci_choose_state(pdev, state));
>         if (err)
>                 goto out;
> 
> First, it breaks some old PowerBooks where the internal OHCI had PM
> feature exposed on PCI (the pmac specific code that follows those lines
> is enough on those machines).
> 
> That can easily be fixed by removing the if (err) goto out; statement
> and having the pmac code set err to 0 in certain conditions, and I'll be
> happy to submit a patch for this.
> 
> However, this raises the question of do we actually want to prevent
> machines to suspend when they have a PCI device that don't have the PCI
> PM capability ? I'm asking that because I can easily imagine that sort
> of construct growing into more drivers (sounds logical if you don't
> think) and I can even imagine somebody thinking it's a good idea to slap
> a __must_check on pci_set_power_state() ... 

As far as the suspend to RAM is concerned, I don't know.

For the suspend to disk we can ignore the error if we know that the device
in question won't do anything like a DMA transfer into memory while we're
creating the suspend image.

Greetings,
Rafael


-- 
You never change things by fighting the existing reality.
		R. Buckminster Fuller
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