linux-kernel - [PATCH v3] PCI: Don't assume root ports from

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Date:   Wed, 24 May 2023 10:21:36 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "S-k Shyam-sundar" <Shyam-sundar.S-k@....com>,
        Natikar Basavaraj <Basavaraj.Natikar@....com>,
        Deucher Alexander <Alexander.Deucher@....com>,
        <linux-pm@...r.kernel.org>, Lukas Wunner <lukas@...ner.de>,
        Mario Limonciello <mario.limonciello@....com>,
        Iain Lane <iain@...ngesquash.org.uk>
Subject: [PATCH v3] PCI: Don't assume root ports from > 2015 are power manageable

Using a USB keyboard or mouse to wakeup the system from s2idle fails when
that XHCI device is connected to a USB-C port for an AMD USB4 router.

Due to commit 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend")
all PCIe ports go into D3 during s2idle.

When specific root ports are put into D3 over s2idle on some AMD platforms
it is not possible for the platform to properly identify wakeup sources.
This happens whether the root port goes into D3hot or D3cold.

Comparing registers between Linux and Windows 11 this behavior to put
these specific root ports into D3 at suspend is unique to Linux. On an
affected system Windows does not put those specific root ports into D3
over Modern Standby.

Windows doesn't put the root ports into D3 because root ports are not
power manageable.

Linux shouldn't assume root ports support D3 just because they're on a
machine newer than 2015, the ports should also be deemed power manageable.
Add an extra check explicitly for root ports to ensure D3 isn't selected
for these ports.

Fixes: 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend")
Reported-by: Iain Lane <iain@...ngesquash.org.uk>
Closes: https://forums.lenovo.com/t5/Ubuntu/Z13-can-t-resume-from-suspend-with-external-USB-keyboard/m-p/5217121
Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
v2->v3:
 * Only apply to root ports
 * Update commit message
---
 drivers/pci/pci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 5ede93222bc1..51126891a2db 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2976,6 +2976,9 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge)

 	switch (pci_pcie_type(bridge)) {
 	case PCI_EXP_TYPE_ROOT_PORT:
+		if (!platform_pci_power_manageable(bridge))
+			return false;
+		fallthrough;
 	case PCI_EXP_TYPE_UPSTREAM:
 	case PCI_EXP_TYPE_DOWNSTREAM:
 		if (pci_bridge_d3_disable)
-- 
2.34.1