[RFC 1/3] PCI/PM: Fix kexec for D3cold and bridge suspending

[Huang Ying <ying.huang@intel.com>]

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.

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);