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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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