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

[Mario Limonciello <superm1@kernel.org>]

On 10/29/26 10:14, Mike Lothian wrote:
> 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

Although your system is a BOCO platform; I do think this same thing for 
this signaling to wakeup could apply to a BACO system too.

> + * (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)

I'd install the notifier for BACO as well.
> +		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);
>   }
>