[PATCH v2] nvme: Look for StorageD3Enable on companion ACPI device instead

[Mario Limonciello]

The documentation around the StorageD3Enable property hints that it
should be made on the PCI device.  This is where AMD systems set
the property and it's required for S0i3 support.

So rather than look for nodes of the root port only present on Intel
systems, switch to the companion ACPI device for all systems.
David Box from Intel indicated this should work on Intel as well.

Link: https://lore.kernel.org/linux-nvme/YK6gmAWqaRmvpJXb@google.com/T/#m900552229fa455867ee29c33b854845fce80ba70
Link: https://docs.microsoft.com/en-us/windows-hardware/design/component-guidelines/power-management-for-storage-hardware-devices-intro
Suggested-by: Prike Liang <Prike.Liang at amd.com>
CC: rrangel at chromium.org
CC: david.e.box at linux.intel.com
CC: Shyam-sundar S-k <Shyam-sundar.S-k at amd.com>
CC: Alexander Deucher <Alexander.Deucher at amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>
---
 drivers/nvme/host/pci.c | 23 +----------------------
 1 file changed, 1 insertion(+), 22 deletions(-)

Changes from v1 to v2:
 * Drop the old PXSX/PEGP logic instead of supplement to it
 * Add references to other discussions on this topic

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index a29b170701fc..d4eef8caa4cc 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2832,9 +2832,6 @@ static unsigned long check_vendor_combination_bug(struct pci_dev *pdev)
 static bool nvme_acpi_storage_d3(struct pci_dev *dev)
 {
 	struct acpi_device *adev;
-	struct pci_dev *root;
-	acpi_handle handle;
-	acpi_status status;
 	u8 val;
 
 	/*
@@ -2842,28 +2839,10 @@ static bool nvme_acpi_storage_d3(struct pci_dev *dev)
 	 * must use D3 to support deep platform power savings during
 	 * suspend-to-idle.
 	 */
-	root = pcie_find_root_port(dev);
-	if (!root)
-		return false;
 
-	adev = ACPI_COMPANION(&root->dev);
+	adev = ACPI_COMPANION(&dev->dev);
 	if (!adev)
 		return false;
-
-	/*
-	 * The property is defined in the PXSX device for South complex ports
-	 * and in the PEGP device for North complex ports.
-	 */
-	status = acpi_get_handle(adev->handle, "PXSX", &handle);
-	if (ACPI_FAILURE(status)) {
-		status = acpi_get_handle(adev->handle, "PEGP", &handle);
-		if (ACPI_FAILURE(status))
-			return false;
-	}
-
-	if (acpi_bus_get_device(handle, &adev))
-		return false;
-
 	if (fwnode_property_read_u8(acpi_fwnode_handle(adev), "StorageD3Enable",
 			&val))
 		return false;
-- 
2.25.1