[PATCH v16 3/3] platform/x86/amd: pmc: Don't let PCIe root ports go into D3

[Mario Limonciello]

commit 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend")
changed pci_bridge_d3_possible() so that any vendor's PCIe ports
from modern machines (>=2015) are allowed to be put into D3.

Iain reports that USB devices can't be used to wake a Lenovo Z13
from suspend. This is because the PCIe root port has been put
into D3 and AMD's platform can't handle USB devices waking from
a hardware sleep state in this case.

This problem only occurs on Linux, and only when the AMD PMC driver
is utilized to put the device into a hardware sleep state. Comparing
the behavior on Windows and Linux, Windows doesn't put the root ports
into D3.

A variety of approaches were discussed to change PCI core to handle this
case generically but no consensus was reached. To limit the scope of
effect only to the affected machines introduce a workaround into the
amd-pmc driver to only apply to the PCI root ports in affected machines
when going into hardware sleep.

Link: https://lore.kernel.org/linux-pci/20230818193932.27187-1-mario.limonciello@xxxxxxx/
Fixes: 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend")
Reported-by: Iain Lane <iain@xxxxxxxxxxxxxxxxxxx>
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@xxxxxxx>
---
v15->v16:
 * Only match PCIe root ports with ACPI companions
 * Use constraints when workaround activated
---
 drivers/platform/x86/amd/pmc/pmc.c | 39 ++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/platform/x86/amd/pmc/pmc.c b/drivers/platform/x86/amd/pmc/pmc.c
index eb2a4263814c..6a037447ec5a 100644
--- a/drivers/platform/x86/amd/pmc/pmc.c
+++ b/drivers/platform/x86/amd/pmc/pmc.c
@@ -741,6 +741,41 @@ static int amd_pmc_czn_wa_irq1(struct amd_pmc_dev *pdev)
 	return 0;
 }
 
+/* only allow PCIe root ports with a LPS0 constraint configured to go to D3 */
+static int amd_pmc_rp_wa(struct amd_pmc_dev *pdev)
+{
+	struct pci_dev *pci_dev = NULL;
+
+	while ((pci_dev = pci_get_device(PCI_VENDOR_ID_AMD, PCI_ANY_ID, pci_dev))) {
+		struct acpi_device *adev;
+		int constraint;
+
+		if (!pci_is_pcie(pci_dev) ||
+		    !(pci_pcie_type(pci_dev) == PCI_EXP_TYPE_ROOT_PORT))
+			continue;
+
+		if (pci_dev->current_state == PCI_D3hot ||
+		    pci_dev->current_state == PCI_D3cold)
+			continue;
+
+		adev = ACPI_COMPANION(&pci_dev->dev);
+		if (!adev)
+			continue;
+
+		constraint = acpi_get_lps0_constraint(adev);
+		if (constraint != ACPI_STATE_UNKNOWN &&
+		    constraint >= ACPI_STATE_S3)
+			continue;
+
+		if (pci_dev->bridge_d3 == 0)
+			continue;
+		pci_dev->bridge_d3 = 0;
+		dev_info(&pci_dev->dev, "Disabling D3 on PCIe root port due lack of constraint\n");
+	}
+
+	return 0;
+}
+
 static int amd_pmc_verify_czn_rtc(struct amd_pmc_dev *pdev, u32 *arg)
 {
 	struct rtc_device *rtc_device;
@@ -893,6 +928,10 @@ static int amd_pmc_suspend_handler(struct device *dev)
 	case AMD_CPU_ID_CZN:
 		rc = amd_pmc_czn_wa_irq1(pdev);
 		break;
+	case AMD_CPU_ID_YC:
+	case AMD_CPU_ID_PS:
+		rc = amd_pmc_rp_wa(pdev);
+		break;
 	default:
 		break;
 	}
-- 
2.34.1