On Fri, Oct 13, 2006 at 10:26:08PM -0700, Andrew Morton wrote:
> On Tue, 10 Oct 2006 07:38:17 -0600
> Matthew Wilcox <[email protected]> wrote:
>
> > Section 5.3 of PCI Bus Power Management 1.2 states:
> >
> > There is a minimum recovery time requirement of 200 ?s between when
> > a function is programmed from D2 to D0 and when the function can be
> > next accessed as a target (including PCI configuration accesses). If
> > an access is attempted in violation of the specified minimum recovery
> > time, undefined system behavior may result.
> >
> > We have to prevent the user running lspci during this time, and
> > fortunately we already have the pci_block_user_cfg_access() API to
> > do this.
> >
> > Signed-off-by: Matthew Wilcox <[email protected]>
> > ---
> > drivers/pci/pci.c | 8 ++++++++
> > 1 files changed, 8 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index a544997..1bb059a 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -366,6 +366,11 @@ pci_set_power_state(struct pci_dev *dev,
> > break;
> > }
> >
> > + /* We have to prevent accesses to config space while transitioning
> > + * between power states
> > + */
> > + pci_block_user_cfg_access(dev);
> > +
> > /* enter specified state */
> > pci_write_config_word(dev, pm + PCI_PM_CTRL, pmcsr);
> >
> > @@ -383,6 +388,9 @@ pci_set_power_state(struct pci_dev *dev,
> > if (platform_pci_set_power_state)
> > platform_pci_set_power_state(dev, state);
> >
> > + /* Should be safe to allow userspace access to the device again now */
> > + pci_unblock_user_cfg_access(dev);
> > +
> > dev->current_state = state;
> >
> > /* According to section 5.4.1 of the "PCI BUS POWER MANAGEMENT
>
> This patch independently causes the same failure: the Vaio doesn't power
> off after suspend-to-disk and after a manual power cycle and resume,
> networking is dead.
>
> The message `acpi_power_off called' never comes out, so something probably
> got stuck.
>
> Or maybe something failed somewhere and the error code which would have
> helped us solve this bug was simply ignored.
>
>
>
> Note that pci_block_user_cfg_access() calls pci_save_state(), which can
> fail. But pci_block_user_cfg_access() discards that information and
> returns void. If this happens, userspace config space reads will return...
> what?
There is a thread right now on the linux-pm mailing list about how this
patch is wrong. I'm going to drop it right now...
thanks,
greg k-h
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