[PATCH 1/2] drm/amdgpu: runtime resume dGPU on ACPI notify from its own node

[Mike Lothian <mike@fireburn.co.uk>]

On BOCO platforms the SBIOS can signal a display hotplug on a powered
off dGPU by notifying the dGPU's ACPI node. On the ASUS ROG Strix G513QY
the USB-C DP alt mode lanes are driven by the Navi 22, and the CPM
D3cold table handles the HPD GPE with only:

  Method (_L05) { Notify (\_SB.PCI0.GPP0.VGA, 0x81) }

Nothing in Linux listens on that node: ATIF is bound to the iGPU and the
dGPU node is not an ACPI video bus. If the dGPU is in D3cold when a dock
is attached it stays off, no hotplug reaches userspace, the external
displays stay dark, and the level-triggered GPE keeps firing until the
dock is removed.

Install an ACPI device notify handler on the dGPU's companion when BOCO
is used, and request a runtime resume on 0x81. Runtime resume already
re-detects all links and sends a hotplug event, so the new displays are
picked up; the device autosuspends again if nothing is enabled.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h      |  1 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 31 ++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 7974f9b7944f..deb63122828d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -641,6 +641,7 @@ struct amdgpu_device {
 	bool				need_swiotlb;
 	bool				accel_working;
 	struct notifier_block		acpi_nb;
+	bool				acpi_dgpu_notify;
 	struct notifier_block		pm_nb;
 	struct amdgpu_i2c_chan		*i2c_bus[AMDGPU_MAX_I2C_BUS];
 	struct debugfs_blob_wrapper debugfs_vbios_blob;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
index 7f5abb03be1b..a4041f90b374 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
@@ -1280,6 +1280,23 @@ static int amdgpu_acpi_event(struct notifier_block *nb,
 	return amdgpu_atif_handler(adev, entry);
 }
 
+/*
+ * On BOCO platforms the SBIOS signals display hotplug on a powered-off dGPU
+ * (e.g. USB-C DP alt mode HPD wired to the dGPU) with Notify(<dGPU>, 0x81)
+ * on the dGPU's own ACPI node. Nothing else listens there, so wake the
+ * device; runtime resume re-detects all links and sends a hotplug event.
+ */
+static void amdgpu_acpi_dgpu_notify(acpi_handle handle, u32 event, void *data)
+{
+	struct amdgpu_device *adev = data;
+
+	if (event != ACPI_VIDEO_NOTIFY_PROBE)
+		return;
+
+	dev_dbg(adev->dev, "ACPI notify 0x%x, requesting runtime resume\n", event);
+	pm_request_resume(adev->dev);
+}
+
 /* Call all ACPI methods here */
 /**
  * amdgpu_acpi_init - init driver acpi support
@@ -1325,6 +1342,14 @@ int amdgpu_acpi_init(struct amdgpu_device *adev)
 	adev->acpi_nb.notifier_call = amdgpu_acpi_event;
 	register_acpi_notifier(&adev->acpi_nb);
 
+	if (!(adev->flags & AMD_IS_APU) && ACPI_COMPANION(adev->dev) &&
+	    adev->pm.rpm_mode == AMDGPU_RUNPM_BOCO)
+		adev->acpi_dgpu_notify =
+			!acpi_dev_install_notify_handler(ACPI_COMPANION(adev->dev),
+							 ACPI_DEVICE_NOTIFY,
+							 amdgpu_acpi_dgpu_notify,
+							 adev);
+
 	return 0;
 }
 
@@ -1344,6 +1369,12 @@ void amdgpu_acpi_get_backlight_caps(struct amdgpu_dm_backlight_caps *caps)
  */
 void amdgpu_acpi_fini(struct amdgpu_device *adev)
 {
+	if (adev->acpi_dgpu_notify) {
+		acpi_dev_remove_notify_handler(ACPI_COMPANION(adev->dev),
+					       ACPI_DEVICE_NOTIFY,
+					       amdgpu_acpi_dgpu_notify);
+		adev->acpi_dgpu_notify = false;
+	}
 	unregister_acpi_notifier(&adev->acpi_nb);
 }
 
-- 
2.56.0