[RFC PATCH 8/9] hda/hdmi: Register with vga_switcheroo on Dual GPU Macbooks

[Orlando Chamberlain]

Commit 586bc4aab878 ("ALSA: hda/hdmi - fix vgaswitcheroo detection for
AMD") caused only AMD gpu's with PX to have their audio component register
with vga_switcheroo. This meant that Apple Macbooks with apple-gmux as the
gpu switcher no longer had the audio client registering, so when the gpu is
powered off by vga_switcheroo snd_hda_intel is unaware that it should have
suspended the device:

amdgpu: switched off
snd_hda_intel 0000:03:00.1:
    Unable to change power state from D3hot to D0, device inaccessible
snd_hda_intel 0000:03:00.1: CORB reset timeout#2, CORBRP = 65535

Simialar to ATPX, we use the presence of an acpi method (PWRD in this
case) to ensure we only register with the correct devices.

Fixes: 586bc4aab878 ("ALSA: hda/hdmi - fix vgaswitcheroo detection for AMD")
Signed-off-by: Orlando Chamberlain <orlandoch.dev@xxxxxxxxx>
---
 sound/pci/hda/hda_intel.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index 87002670c0c9..c97bbe60e603 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -1435,11 +1435,25 @@ static bool atpx_present(void)
 	}
 	return false;
 }
+
+static bool pwrd_present(struct pci_dev *pci)
+{
+	acpi_handle pwrd_handle;
+	acpi_status status;
+
+	status = acpi_get_handle(ACPI_HANDLE(&pci->dev), "PWRD", &pwrd_handle);
+	return ACPI_FAILURE(status) ? false : true;
+}
 #else
 static bool atpx_present(void)
 {
 	return false;
 }
+
+static bool pwrd_present(struct pci_dev *pci)
+{
+	return false;
+}
 #endif
 
 /*
@@ -1461,9 +1475,12 @@ static struct pci_dev *get_bound_vga(struct pci_dev *pci)
 				 * rather than the dGPU's namespace. However,
 				 * the dGPU is the one who is involved in
 				 * vgaswitcheroo.
+				 *
+				 * PWRD is in the dGPU's ACPI namespace on Apple
+				 * Macbooks with dual gpu's.
 				 */
 				if (((p->class >> 16) == PCI_BASE_CLASS_DISPLAY) &&
-				    atpx_present())
+						(atpx_present() || pwrd_present(p)))
 					return p;
 				pci_dev_put(p);
 			}
-- 
2.39.1