PCI/PM: Restore BARs after powering up during enumeration

Commit 4d4c10f763d7 ("PCI: Explicitly put devices into D0 when
initializing") added pci_pm_power_up_and_verify_state() to pci_pm_init().
The helper ignores pci_power_up()'s return value indicating that BARs need
restoring. Its resume callers restore saved configuration afterwards;
pci_pm_init() does not.

D3hot-to-D0 may reset a device and lose its BARs (PCI PM 1.2, sec 5.4.1).
After enumeration powers it up, pci_enable_device() reads D0 and skips the
full power-up path. Previously, a device still in D3hot at enable time took
that path, including BAR restoration.

On AMD Venice SP7, two AMD xHCI controllers [1022:17d2] are in runtime
D3hot with No_Soft_Reset clear before kdump. Diagnostic reads on
v7.3-rc6-37 show the following for 0000:01:00.4 in the crash kernel:

                                   PMCSR      BAR0
  before the platform power call   0003       f4100004
  after the platform power call    0003       f4100004
  after native D0 power-up         0000       00000004

The upper BAR DWORD stays zero. pci_power_up() returns 1, but the BAR
address remains zero while dev->resource[0] still contains 0xf4100000.
Without BAR restoration, the crash kernel hangs during boot. The last
console output includes:

  pci 0000:01:00.4: enabling device (0000 -> 0002)

Restoring both controllers' BARs gives matching readbacks and allows kdump
to save a vmcore and reboot. An AMD Turin xHCI [1022:1557] shows the same
BAR loss; restoring its BAR also allows kdump to complete.

Read the initial power state first. Otherwise, pci_power_up() may request a
BAR restore based on a cached PCI_UNKNOWN state, even when the device is
already in D0.

For devices already in D0, only synchronize the platform state so
that ACPI calls such as _REG still run. For other states, use
pci_set_full_power_state() to power up the device and restore BARs
when needed.

Fixes: 4d4c10f763d7 ("PCI: Explicitly put devices into D0 when initializing")
Suggested-by: Mario Limonciello <mario.limonciello@amd.com>
Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/CAJZ5v0ie2AvCbdv8-zkpYzHLcTwUPUj+=WWOQjDAPmSepSAQPg@mail.gmail.com/
Signed-off-by: Keng-Yu Lin <keng-yu.lin@hpe.com>
[bhelgaas: shorten comment]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>> ---
Reviewed-by: Desnes Nunes <desnesn@redhat.com>
Reviewed-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20261015020811.1132314-1-keng-yu.lin@hpe.com

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