PCI: Set device power state to PCI_D0 for device without native PM support

Hi Jesse,

Have following query, please point me to correct person if I am asking this to wrong person:
Any particular reason, why this is not checked in yet? Is something missing here?

Thanks,
Ajay

-------- Original Message --------
Subject: Re: [PATCH] PCI: Set device power state to PCI_D0 for device
without native PM support
Date: Fri, 28 Oct 2011 17:36:43 +0530
From: Ajaykumar Hotchandani <[email protected]>
To: Jesse Barnes <[email protected]>,
"[email protected]" <[email protected]>, "[email protected]" <[email protected]>
CC: Stefano Stabellini <[email protected]>, Yinghai Lu
<[email protected]>

Quoted 8 lines · Stefano Stabellini

Quoted 5 lines · Ajaykumar Hotchandani

Quoted 1 line

BTW I am OK with your patch.

Should we revert 47e9037ac16637cd7f12b8790ea7ce6680e42168 (your changes in register_slot() )
I think, after this change, it's not needed. Or, am I missing some scenario?

I think you are right, 47e9037ac16637cd7f12b8790ea7ce6680e42168 is not needed anymore, so I am OK with reverting it.

Thanks, following is updated patch.

[PATCH -v2] 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.

-v2: This also reverts 47e9037ac16637cd7f12b8790ea7ce6680e42168, as it's not needed after this change.

Signed-off-by Ajaykumar Hotchandani<[email protected]>

Signed-off-by Yinghai Lu<[email protected]>

---
  drivers/pci/hotplug/acpiphp_glue.c |    1 -
  drivers/pci/pci.c                  |    3 +++
  2 files changed, 3 insertions(+), 1 deletions(-)

drivers/pci/hotplug/acpiphp_glue.c +0 -1

index 2202857..11431c1 100644
@@ -212,7 +212,6 @@ register_slot(acpi_handle handle, u32 lvl, void
 *context, void **rv)
 
         pdev = pci_get_slot(pbus, PCI_DEVFN(device, function));
         if (pdev) {
-               pdev->current_state = PCI_D0;
                 slot->flags |= (SLOT_ENABLED | SLOT_POWEREDON);
                 pci_dev_put(pdev);

         }

drivers/pci/pci.c +3 -0

index e9651f0..6866937 100644
@@ -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 */
+               if (!dev->pm_cap)
+                       dev->current_state = PCI_D0;
         } else {
                 error = -ENODEV;

                 /* Fall back to PCI_D0 if native PM is not supported */