[PATCH v3 1/2] PCI/PM: Skip resuming to D0 if disconnected

[Mario Limonciello <superm1@kernel.org>]

From: Mario Limonciello <mario.limonciello@amd.com>

When a USB4 dock is unplugged the PCIe bridge it's connected to will
remove issue a "Link Down" and "Card not detected event". The PCI core
will treat this as a surprise hotplug event and unconfigure all downstream
devices. This involves setting the device error state to
`pci_channel_io_perm_failure` which pci_dev_is_disconnected() will check.

It doesn't make sense to runtime resume disconnected devices to D0 and
report the (expected) error to do so.  It is still useful information
that a device is disconnected though, so add an info message for that
purpose.

Suggested-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
v3:
 * Adjust text and subject
 * Add an info message instead
v2:
 * Use pci_dev_is_disconnected()
v1: https://lore.kernel.org/linux-usb/20250609020223.269407-1-superm1@kernel.org/T/#mf95c947990d016fbfccfd11afe60b8ae08aafa0b
---
 drivers/pci/pci.c | 5 +++++
 drivers/pci/pci.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 9e42090fb1089..160a9a482c732 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1374,6 +1374,11 @@ int pci_power_up(struct pci_dev *dev)
 		return -EIO;
 	}
 
+	if (pci_dev_is_disconnected(dev)) {
+		dev->current_state = PCI_D3cold;
+		return -EIO;
+	}
+
 	pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
 	if (PCI_POSSIBLE_ERROR(pmcsr)) {
 		pci_err(dev, "Unable to change power state from %s to D0, device inaccessible\n",
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 12215ee72afb6..57aaf9c63e2e8 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -550,6 +550,7 @@ static inline bool pci_dev_set_io_state(struct pci_dev *dev,
 
 static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused)
 {
+	pci_info(dev, "Device disconnected\n");
 	pci_dev_set_io_state(dev, pci_channel_io_perm_failure);
 	pci_doe_disconnected(dev);
 
-- 
2.43.0