[PATCH] PCI: PM: Also move to D0 before calling pci_legacy_resume_early()

[Dexuan Cui <decui@microsoft.com>]

In pci_legacy_suspend_late(), the device state is moved to PCI_UNKNOWN.
In pci_pm_thaw_noirq(), the state is supposed to be moved back to PCI_D0,
but the current code misses the pci_legacy_resume_early() path, so the
state remains in PCI_UNKNOWN in that path, and during hiberantion this
causes an error for the Mellanox VF driver, which fails to enable
MSI-X: pci_msi_supported() is false due to dev->current_state != PCI_D0:

mlx4_core a6d1:00:02.0: Detected virtual function - running in slave mode
mlx4_core a6d1:00:02.0: Sending reset
mlx4_core a6d1:00:02.0: Sending vhcr0
mlx4_core a6d1:00:02.0: HCA minimum page size:512
mlx4_core a6d1:00:02.0: Timestamping is not supported in slave mode
mlx4_core a6d1:00:02.0: INTx is not supported in multi-function mode, aborting
PM: dpm_run_callback(): pci_pm_thaw+0x0/0xd7 returns -95
PM: Device a6d1:00:02.0 failed to thaw: error -95

Signed-off-by: Dexuan Cui <decui@microsoft.com>
---
 drivers/pci/pci-driver.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 36dbe960306b..27dfc68db9e7 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -1074,15 +1074,16 @@ static int pci_pm_thaw_noirq(struct device *dev)
 			return error;
 	}
 
-	if (pci_has_legacy_pm_support(pci_dev))
-		return pci_legacy_resume_early(dev);
-
 	/*
 	 * pci_restore_state() requires the device to be in D0 (because of MSI
 	 * restoration among other things), so force it into D0 in case the
 	 * driver's "freeze" callbacks put it into a low-power state directly.
 	 */
 	pci_set_power_state(pci_dev, PCI_D0);
+
+	if (pci_has_legacy_pm_support(pci_dev))
+		return pci_legacy_resume_early(dev);
+
 	pci_restore_state(pci_dev);
 
 	if (drv && drv->pm && drv->pm->thaw_noirq)
-- 
2.19.1