[PATCH 3/5] PCI / PM: Check for error when reading PME status

[Bjorn Helgaas]

From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

pci_check_pme_status() reads the Power Management capability to determine
whether a device has generated a PME.  The capability is in config space,
which is accessible in D0, D1, D2, and D3hot, but not in D3cold.

If we call pci_check_pme_status() on a device that's in D3cold, config
reads fail and return ~0 data, which we erroneously interpreted as "the
device has generated a PME".

000dd5316e1c ("PCI: Do not poll for PME if the device is in D3cold")
avoided many of these problems by avoiding pci_check_pme_status() if we
think the device is in D3cold.  However, it is not a complete fix because
the device may go to D3cold after we check its power state but before
pci_check_pme_status() reads the Power Management Status Register.

Return false ("device has not generated a PME") if we get an error response
reading the Power Management Status Register.

Fixes: 000dd5316e1c ("PCI: Do not poll for PME if the device is in D3cold")
Fixes: 71a83bd727cc ("PCI/PM: add runtime PM support to PCIe port")
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
---
 drivers/pci/pci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 984171d40858..af6a97d7012b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2008,6 +2008,9 @@ bool pci_check_pme_status(struct pci_dev *dev)
 
 	pmcsr_pos = dev->pm_cap + PCI_PM_CTRL;
 	pci_read_config_word(dev, pmcsr_pos, &pmcsr);
+	if (pmcsr == (u16) PCI_ERROR_RESPONSE)
+		return false;
+
 	if (!(pmcsr & PCI_PM_CTRL_PME_STATUS))
 		return false;
 
-- 
2.22.0.770.g0f2c4a37fd-goog