Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: PCI PM: Restore standard config registers of all devices early | Date | Mon, 2 Feb 2009 22:32:33 +0100 |
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On Monday 02 February 2009, Benjamin Herrenschmidt wrote: > On Mon, 2009-02-02 at 12:41 -0800, Linus Torvalds wrote: > > > > On Tue, 3 Feb 2009, Benjamin Herrenschmidt wrote: > > > > > > I'd rather hook it up inside pci_set_power_state()... > > > > Umm. But you already _have_ that. Look at platform_pci_set_power_state(). > > It gets called before turning the device on (pci_raw_set_power_state(D0)) > > and after turning the device off (pci_raw_set_power_state(D1+)) > > > > Maybe you missed it? It's how ACPI does things. > > I may well have, it didn't exist when my stuff was written. > > > However, the issue you see is that pci_restore_standard_config() doesn't > > call it, because at least with ACPI, the ACPI code simply isn't ready to > > be called with interrupts off. So it looks like you may be looking at the > > wrong thing, hmm? > > Well.. yes and no... I still don't see how it can be sane to whack config > space back before the device has been turned back on. I wouldn't be surprised > if some devices don't grok well their BARs being written while not in D0. > > I suppose I can always add another hook inside pci_restore_blah for my specific > case but I can also very easily see that can of worms hitting even more badly > in tight embedded environments such as handhelds, who use things like fine clock > control a lot more extensively. > > In fact, even on x86, I'm not sure it's kosher to restore the config space > before you called ACPI...
It need not be in theory, but I haven't seen any real life example of that.
I think devices without the PM capability are suspicious, so to speak.
Thanks, Rafael
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