On Sat, 14 Oct 2006 21:20:01 -0600
Matthew Wilcox <[email protected]> wrote:
> On Sat, Oct 14, 2006 at 01:48:55PM -0700, Andrew Morton wrote:
> > On Sat, 14 Oct 2006 08:02:49 -0600
> > Matthew Wilcox <[email protected]> wrote:
> >
> > > On Fri, Oct 13, 2006 at 09:41:35PM -0700, Andrew Morton wrote:
> > > > Bisection shows that this patch
> > > > (pci-check-that-mwi-bit-really-did-get-set.patch in Greg's PCI tree) breaks
> > > > suspend-to-disk on my Vaio. It writes the suspend image and gets to the
> > > > point where it's supposed to power down, but doesn't.
> > >
> > > How odd. What driver is calling pci_set_mwi() on the suspend path?
> >
> > ehci_pci_reinit(). I stuck a dump_stack() in there. See
> > http://userweb.kernel.org/~akpm/s5000342.jpg
>
> Thanks for the picture; that's really helpful.
>
> I see. We hibernate all the devices then wake them all back up again.
> No doubt there's a good reason for this.
>
> Still doesn't make much sense, though. As far as I can see, the only
> consequence of this particular patch is that 1) we do an additional read
> from PCI_COMMAND and 2) we can return -EINVAL in one additional case.
> But the only effect of returning EINVAL is a printk (for this particular
> driver):
>
> /* PCI Memory-Write-Invalidate cycle support is optional (uncommon) */
> retval = pci_set_mwi(pdev);
> if (!retval)
> ehci_dbg(ehci, "MWI active\n");
>
> ehci_port_power(ehci, 0);
>
> return 0;
>
> So even if we return EINVAL ... big deal.
>
> Is it possible reading PCI_COMMAND too quickly after writing it causes
> a foul-up? That would be weird ...
>
> so I suppose there's a few things I can ask you to try:
It seems to have stopped happening. I don't know why.
gregkh-pci-pci-prevent-user-config-space-access-during-power-state-transitions.patch
still breaks suspend though: http://userweb.kernel.org/~akpm/s5000349.jpg
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