Hi,
On Wednesday, October 05, 2011, Ajaykumar Hotchandani wrote:
> 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@xxxxxxxxxx>
> Signed-off-by: Yinghai Lu<yinghai.lu@xxxxxxxxxx>
> ---
> 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 */
>
I have some vague memories that we tried that and it broke something.
How thoroughly has it been tested?
Rafael
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