amd64-agp: convert to generic power management

Convert amd64-agp from legacy PCI power management to the generic power
management framework.

Previously, amd64-agp used legacy PCI power management, and
agp_amd64_suspend() and agp_amd64_resume() were responsible for both
device-specific things and generic PCI things:

  agp_amd64_suspend
    pci_save_state(pdev)                <-- generic PCI
    pci_set_power_state(pdev, pci_choose_state(pdev, state)) <-- generic PCI

  agp_amd64_resume
    pci_set_power_state(pdev, PCI_D0)   <-- generic PCI
    pci_restore_state(pdev)             <-- generic PCI
    nforce3_agp_init()                  <-- device-specific
    amd_8151_configure()                <-- device-specific

With generic power management, the PCI bus PM methods do the generic PCI
things, and the driver needs only the device-specific part, i.e.,

  suspend_devices_and_enter
    dpm_suspend_start(PMSG_SUSPEND)
      pci_pm_suspend                    # PCI bus .suspend() method
        agp_amd64_suspend               <-- not needed at all; removed
    suspend_enter
      dpm_suspend_noirq(PMSG_SUSPEND)
        pci_pm_suspend_noirq            # PCI bus .suspend_noirq() method
          pci_save_state                <-- generic PCI
          pci_prepare_to_sleep          <-- generic PCI
            pci_set_power_state
    ...
    dpm_resume_end(PMSG_RESUME)
      pci_pm_resume                     # PCI bus .resume() method
        pci_restore_standard_config
          pci_set_power_state(PCI_D0)   <-- generic PCI
          pci_restore_state             <-- generic PCI
        agp_amd64_resume                # dev->driver->pm->resume
          nforce3_agp_init()            <-- device-specific
          amd_8151_configure()          <-- device-specific

[bhelgaas: commit log]
Link: https://lore.kernel.org/r/20211208193305.147072-2-helgaas@kernel.org
Signed-off-by: Vaibhav Gupta <vaibhavgupta40@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Dave Airlie <airlied@redhat.com>

drivers/char/agp/amd64-agp.c

@@ -588,20 +588,11 @@ static void agp_amd64_remove(struct pci_dev *pdev)
 	agp_bridges_found--;
 }
 
-#ifdef CONFIG_PM
+#define agp_amd64_suspend NULL
 
-static int agp_amd64_suspend(struct pci_dev *pdev, pm_message_t state)
+static int __maybe_unused agp_amd64_resume(struct device *dev)
 {
-	pci_save_state(pdev);
-	pci_set_power_state(pdev, pci_choose_state(pdev, state));
-
-	return 0;
-}
-
-static int agp_amd64_resume(struct pci_dev *pdev)
-{
-	pci_set_power_state(pdev, PCI_D0);
-	pci_restore_state(pdev);
+	struct pci_dev *pdev = to_pci_dev(dev);
 
 	if (pdev->vendor == PCI_VENDOR_ID_NVIDIA)
 		nforce3_agp_init(pdev);
@@ -609,8 +600,6 @@ static int agp_amd64_resume(struct pci_dev *pdev)
 	return amd_8151_configure();
 }
 
-#endif /* CONFIG_PM */
-
 static const struct pci_device_id agp_amd64_pci_table[] = {
 	{
 	.class		= (PCI_CLASS_BRIDGE_HOST << 8),
@@ -738,15 +727,14 @@ static const struct pci_device_id agp_amd64_pci_promisc_table[] = {
 	{ }
 };
 
+static SIMPLE_DEV_PM_OPS(agp_amd64_pm_ops, agp_amd64_suspend, agp_amd64_resume);
+
 static struct pci_driver agp_amd64_pci_driver = {
 	.name		= "agpgart-amd64",
 	.id_table	= agp_amd64_pci_table,
 	.probe		= agp_amd64_probe,
 	.remove		= agp_amd64_remove,
-#ifdef CONFIG_PM
-	.suspend	= agp_amd64_suspend,
-	.resume		= agp_amd64_resume,
-#endif
+	.driver.pm  = &agp_amd64_pm_ops,
 };