linux-kernel - Re: PCI PM: Restore standard config registers of all devices early

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Date:	Mon, 2 Feb 2009 09:06:42 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jesse.barnes@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Andreas Schwab <schwab@...e.de>
Subject: Re: PCI PM: Restore standard config registers of all devices early



On Mon, 2 Feb 2009, Benjamin Herrenschmidt wrote:
> 
> I don't know how x86 does but I'm sure there must be some kind ACPI
> thingy that must be called too before you can touch a device, in case it
> got powered off by more than just the standard D states (ie, clock
> stopped on the bus or whole power plane switched off).

It gets called later in that case.

> I'll try to reproduce and think about it more, but it looks to me that
> this patch might not be quite the right approach yet.

I think you'll need to move the clock gating thing to be a sysdev 
suspend/resume event, which gets done really early along with things like 
core timekeeping etc. We kind of hit that already with the USB driver, 
where CONFIG_PPC does all kinds of wrong things:

	#ifdef CONFIG_PPC_PMAC
	        if (retval == 0) {
	                /* Disable ASIC clocks for USB */
	                if (machine_is(powermac)) {
	                        struct device_node      *of_node;

	                        of_node = pci_device_to_OF_node(dev);
	                        if (of_node)
	                                pmac_call_feature(PMAC_FTR_USB_ENABLE,
	                                                        of_node, 0, 0);
	                }
	        }
	#endif

inside the hcd-pci.c driver. If that whole thing was a sysdev feature, you 
wouldn't need that kind of insane "do my own arch-specific thing in a 
generic driver" thing. AND waking it up would work too.

I'm assuming this is exactly the kind of thing that is now biting you?

		Linus
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