ALSA: hda/hdmi - fix vgaswitcheroo detection for AMD

Only enable the vga_switcheroo logic on systems with the
ATPX ACPI method.  This logic is not needed for asics
that are not part of a PX (PowerXpress)/HG (Hybrid Graphics)
platform.
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://lore.kernel.org/r/20191122214353.582899-2-alexander.deucher@amd.comSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/hda_intel.c

@@ -35,6 +35,7 @@
 #include <linux/clocksource.h>
 #include <linux/time.h>
 #include <linux/completion.h>
+#include <linux/acpi.h>
 
 #ifdef CONFIG_X86
 /* for snoop control */
@@ -1401,6 +1402,34 @@ static int azx_dev_free(struct snd_device *device)
 }
 
 #ifdef SUPPORT_VGA_SWITCHEROO
+#ifdef CONFIG_ACPI
+/* ATPX is in the integrated GPU's namespace */
+static bool atpx_present(void)
+{
+	struct pci_dev *pdev = NULL;
+	acpi_handle dhandle, atpx_handle;
+	acpi_status status;
+
+	while ((pdev = pci_get_class(PCI_BASE_CLASS_DISPLAY << 16, pdev)) != NULL) {
+		dhandle = ACPI_HANDLE(&pdev->dev);
+		if (dhandle) {
+			status = acpi_get_handle(dhandle, "ATPX", &atpx_handle);
+			if (!ACPI_FAILURE(status)) {
+				pci_dev_put(pdev);
+				return true;
+			}
+		}
+		pci_dev_put(pdev);
+	}
+	return false;
+}
+#else
+static bool atpx_present(void)
+{
+	return false;
+}
+#endif
+
 /*
  * Check of disabled HDMI controller by vga_switcheroo
  */
@@ -1412,6 +1441,22 @@ static struct pci_dev *get_bound_vga(struct pci_dev *pci)
 	switch (pci->vendor) {
 	case PCI_VENDOR_ID_ATI:
 	case PCI_VENDOR_ID_AMD:
+		if (pci->devfn == 1) {
+			p = pci_get_domain_bus_and_slot(pci_domain_nr(pci->bus),
+							pci->bus->number, 0);
+			if (p) {
+				/* ATPX is in the integrated GPU's ACPI namespace
+				 * rather than the dGPU's namespace. However,
+				 * the dGPU is the one who is involved in
+				 * vgaswitcheroo.
+				 */
+				if (((p->class >> 16) == PCI_BASE_CLASS_DISPLAY) &&
+				    atpx_present())
+					return p;
+				pci_dev_put(p);
+			}
+		}
+		break;
 	case PCI_VENDOR_ID_NVIDIA:
 		if (pci->devfn == 1) {
 			p = pci_get_domain_bus_and_slot(pci_domain_nr(pci->bus),