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Subject[PATCH] PCI: Set device power state to PCI_D0 for device without native PM support
During test of one IB card with guest VM, found that, msi is not initialized properly.

It turns out __write_msi_msg will do nothing if device current_state is not PCI_D0.
And, that pci device does not have pm_cap in guest VM.

There is an error in setting of power state to PCI_D0 in pci_enable_device(), but error is not returned for this.
Following is code flow:
pci_enable_device() --> __pci_enable_device_flags() --> do_pci_enable_device() --> pci_set_power_state() --> __pci_start_power_transition()
We have following condition inside __pci_start_power_transition():
if (platform_pci_power_manageable(dev)) {
error = platform_pci_set_power_state(dev, state);
if (!error)
pci_update_current_state(dev, state);
} else {
error = -ENODEV;
/* Fall back to PCI_D0 if native PM is not supported */
if (!dev->pm_cap)
dev->current_state = PCI_D0;
}
Here, from platform_pci_set_power_state(), acpi_pci_set_power_state() is getting called and that is failing with ENODEV because of following condition:
if (!handle || ACPI_SUCCESS(acpi_get_handle(handle, "_EJ0",&tmp)))
return -ENODEV;
Because of that, pci_update_current_state() is not getting called.

With this patch, if device power state can not be set via platform_pci_set_power_state and that device does not have native pm support, then PCI device power state will be set to PCI_D0.

Signed-off-by: Ajaykumar Hotchandani<ajaykumar.hotchandani@oracle.com>
Signed-off-by: Yinghai Lu<yinghai.lu@oracle.com>
---
drivers/pci/pci.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e9651f0..ca8c82d 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -664,6 +664,9 @@ static int pci_platform_power_transition(struct pci_dev *dev, pci_power_t state)
error = platform_pci_set_power_state(dev, state);
if (!error)
pci_update_current_state(dev, state);
+ /* Fall back to PCI_D0 if native PM is not supported */
+ else if (!dev->pm_cap)
+ dev->current_state = PCI_D0;
} else {
error = -ENODEV;
/* Fall back to PCI_D0 if native PM is not supported */
--
1.7.5.1


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