Re: PCI: Fix boot-time hang on G31/G33 PC

From: Kok, Auke
Date: Thu Sep 27 2007 - 14:36:55 EST

Ivan Kokshaysky wrote:
> On Wed, Sep 26, 2007 at 03:20:40PM -0700, Jesse Barnes wrote:
>> Ivan, your concern is about disabling things like interrupt controllers
>> and power management chips during probe right? You're right that doing
>> that could cause problems if we get and interrupt or PMU event at just
>> the wrong time, but that could just as easily happen if decode was
>> still enabled but the BAR had a bogus address programmed (as it would
>> during probing).
> Yes, nobody is arguing that moving the BAR around is unsafe, but generally
> it's the less of two evils.
> The major problem here is that with IO and MEM bits cleared in the command
> register you disable *all* address decoders on the device, not just ranges
> that have respective BARs. At least this behaviour is required by PCI spec.
> Examples:
> - legacy VGA IO and memory (no corresponding BARs);
> - base/limit registers of P2P bridge;
> - PMU and SMBus registers (sort of normal BARs, but hidden elsewhere
> in the config space);
> - IDE legacy mode registers;
> - IO-APIC registers (typically sort of read-only BAR).
> For all of these address ranges our current BAR probe is effectively
> a no-op, but disable/re-enable clearly isn't.
>> Ultimately, I don't care much one way or another as long as we can get
>> the desktop platforms fixed somehow. I think disabling decode is the
>> most correct way of doing this, but I'm open to other solutions (this
>> is the only patch I've seen though that's been tested to solve the
>> problem).
> There are two other solutions: one is to disable decode selectively,
> only on devices or systems where it's necessary and known to be safe.
> I've posted a patch which introduces "disable_while_probe" pci_dev field
> for that purpose.
> Another one is to delay mmconfig probe until after the PCI probe is done,
> as Matthew suggested, and Robert confirmed that it's feasible.

for everyone who's using this quirk or has the same boot issue: I just confirmed
that the new dg33tl bios update v0287 (released 9/20) fixes the boot issue for my
systems. I encourage everyone to update their BIOS image and see if this works.


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