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    SubjectRe: [RFC 1/3] PCI/PM: Fix kexec for D3cold and bridge suspending
    Huang Ying <ying.huang@intel.com> writes:

    > On Thu, 2012-09-20 at 00:38 -0700, Eric W. Biederman wrote:
    >> Bjorn Helgaas <bhelgaas@google.com> writes:
    >>
    >> > +cc Eric and kexec list
    >> >
    >> > On Mon, Sep 17, 2012 at 2:54 AM, Huang Ying <ying.huang@intel.com> wrote:
    >> >> If PCI devices are put into D3cold before kexec, because the
    >> >> configuration registers of PCI devices in D3cold are not accessible.
    >> >>
    >> >> And if PCI bridges are put into low power state before kexec,
    >> >> configuration registers of PCI devices underneath the PCI bridges are
    >> >> not accessible too.
    >> >>
    >> >> These will make some PCI devices can not be scanned after kexec, so
    >> >> resume the PCI devices in D3cold or PCI bridges in low power state
    >> >> before kexec.
    >> >
    >> > Don't we need to resume the device even without the kexec issue? And
    >> > even if it's in D1 or D2?
    >>
    >> The basic requirement is that the device needs to be visible so we can
    >> auto discover it. As I recall most sleep states don't make the device
    >> invisible and we can handle the rest in the device initializatoin code.
    >
    > PCI devices in D3cold or under a bridge in D3hot will not be visible, so
    > we must fix that for kexec to run properly.

    That seems reasonable to me.

    >> > It looks to me like pci_msi_shutdown() (and probably drv->shutdown())
    >> > depend on the device being in D0.
    >>
    >> There is certainly a depenency on the config registers being visible.
    >> Although I don't know if much will go wrong if they aren't.
    >>
    >> Ceratinly pci_msi_shutdown doesn't have anything to do if the device has
    >> had so much power removed that the device is not even exectuing.
    >
    > Don't know which power state device should be in for pci_msi_shutdown
    > etc. But it appears that normal shutdown/reboot and kexec works at most
    > times so far. D3cold and bridge in D3hot works for normal
    > shutdown/reboot, but not for kexec. So I write some fix.

    To be clear. Has someone picked up this patch yet?

    Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>

    As for reboot it tends to always work because frequently the firmware
    code triggers a soft reset of the entire machine, which puts devices in
    their power on reset state, which is not a suspended state. Although
    that behavior is not required for a software reboot.

    Eric



    > Best Regards,
    > Huang Ying
    >
    >> >> Signed-off-by: Huang Ying <ying.huang@intel.com>
    >> >> ---
    >> >> drivers/pci/pci-driver.c | 4 ++++
    >> >> 1 file changed, 4 insertions(+)
    >> >>
    >> >> --- a/drivers/pci/pci-driver.c
    >> >> +++ b/drivers/pci/pci-driver.c
    >> >> @@ -421,6 +421,10 @@ static void pci_device_shutdown(struct d
    >> >> struct pci_dev *pci_dev = to_pci_dev(dev);
    >> >> struct pci_driver *drv = pci_dev->driver;
    >> >>
    >> >> + /* Resume bridges and devices in D3cold for kexec to work properly */
    >> >> + if (pci_dev->current_state == PCI_D3cold || pci_dev->subordinate)
    >> >> + pm_runtime_resume(dev);
    >> >> +
    >> >> if (drv && drv->shutdown)
    >> >> drv->shutdown(pci_dev);
    >> >> pci_msi_shutdown(pci_dev);
    >> >
    >> > _______________________________________________
    >> > kexec mailing list
    >> > kexec@lists.infradead.org
    >> > http://lists.infradead.org/mailman/listinfo/kexec


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