drm/nouveau: Use generic helper to check _PR3 presence

Replace nouveau_pr3_present() in favor of a more generic one,
pci_pr3_present().

Also the presence of upstream bridge _PR3 doesn't need to go hand in
hand with device's _DSM, so check _PR3 before _DSM.
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_acpi.c

@@ -211,37 +211,6 @@ static const struct vga_switcheroo_handler nouveau_dsm_handler = {
 	.get_client_id = nouveau_dsm_get_client_id,
 };
 
-/*
- * Firmware supporting Windows 8 or later do not use _DSM to put the device into
- * D3cold, they instead rely on disabling power resources on the parent.
- */
-static bool nouveau_pr3_present(struct pci_dev *pdev)
-{
-	struct pci_dev *parent_pdev = pci_upstream_bridge(pdev);
-	struct acpi_device *parent_adev;
-
-	if (!parent_pdev)
-		return false;
-
-	if (!parent_pdev->bridge_d3) {
-		/*
-		 * Parent PCI bridge is currently not power managed.
-		 * Since userspace can change these afterwards to be on
-		 * the safe side we stick with _DSM and prevent usage of
-		 * _PR3 from the bridge.
-		 */
-		pci_d3cold_disable(pdev);
-		return false;
-	}
-
-	parent_adev = ACPI_COMPANION(&parent_pdev->dev);
-	if (!parent_adev)
-		return false;
-
-	return parent_adev->power.flags.power_resources &&
-		acpi_has_method(parent_adev->handle, "_PR3");
-}
-
 static void nouveau_dsm_pci_probe(struct pci_dev *pdev, acpi_handle *dhandle_out,
 				  bool *has_mux, bool *has_opt,
 				  bool *has_opt_flags, bool *has_pr3)
@@ -249,6 +218,16 @@ static void nouveau_dsm_pci_probe(struct pci_dev *pdev, acpi_handle *dhandle_out
 	acpi_handle dhandle;
 	bool supports_mux;
 	int optimus_funcs;
+	struct pci_dev *parent_pdev;
+
+	*has_pr3 = false;
+	parent_pdev = pci_upstream_bridge(pdev);
+	if (parent_pdev) {
+		if (parent_pdev->bridge_d3)
+			*has_pr3 = pci_pr3_present(parent_pdev);
+		else
+			pci_d3cold_disable(pdev);
+	}
 
 	dhandle = ACPI_HANDLE(&pdev->dev);
 	if (!dhandle)
@@ -269,7 +248,6 @@ static void nouveau_dsm_pci_probe(struct pci_dev *pdev, acpi_handle *dhandle_out
 	*has_mux = supports_mux;
 	*has_opt = !!optimus_funcs;
 	*has_opt_flags = optimus_funcs & (1 << NOUVEAU_DSM_OPTIMUS_FLAGS);
-	*has_pr3 = false;
 
 	if (optimus_funcs) {
 		uint32_t result;
@@ -279,8 +257,6 @@ static void nouveau_dsm_pci_probe(struct pci_dev *pdev, acpi_handle *dhandle_out
 			 (result & OPTIMUS_ENABLED) ? "enabled" : "disabled",
 			 (result & OPTIMUS_DYNAMIC_PWR_CAP) ? "dynamic power, " : "",
 			 (result & OPTIMUS_HDA_CODEC_MASK) ? "hda bios codec supported" : "");
-
-		*has_pr3 = nouveau_pr3_present(pdev);
 	}
 }