Re: [PATCH 2/3] drm/amdgpu: add Apple GMUX runtime PM support

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] This problem wasn't introduced by this patch, but switch_power_state remains permanently stuck in DRM_SWITCH_POWER_CHANGING on suspend/resume failure.
--

--- Patch [2]: [PATCH 2/3] drm/amdgpu: add Apple GMUX runtime PM support ---
commit 2067ef2b3a267308c80f88d728f87fe7fad945a3
Author: Andre Eikmeyer <[email protected]>

    drm/amdgpu: add Apple GMUX runtime PM support
    
    The MacBookPro15,1 uses Apple GMUX to control power to the discrete GPU,
    but it does not expose the ATPX or ACPI power-resource interfaces currently
    recognized by amdgpu. The driver therefore leaves runtime PM disabled even
    though vga_switcheroo can switch the GPU reliably.

[ ... ]

> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index 0ab380ca7e645..a231a002831bb 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
[ ... ]
> @@ -2872,7 +2875,8 @@ static int amdgpu_pmops_runtime_suspend(struct device *dev)
>  	}
>  
>  	adev->in_runpm = true;
> -	if (adev->pm.rpm_mode == AMDGPU_RUNPM_PX)
> +	if (adev->pm.rpm_mode == AMDGPU_RUNPM_PX ||
> +	    adev->pm.rpm_mode == AMDGPU_RUNPM_GMUX)
>  		drm_dev->switch_power_state = DRM_SWITCH_POWER_CHANGING;

[Severity: High]
This is a pre-existing issue, but I noticed that switch_power_state can be
left permanently stuck in DRM_SWITCH_POWER_CHANGING if a failure occurs here.

Looking at amdgpu_pmops_runtime_suspend(), if amdgpu_device_suspend() fails,
it returns early:

	ret = amdgpu_device_suspend(drm_dev, false);
	if (ret) {
		adev->in_runpm = false;
		if (adev->pm.rpm_mode == AMDGPU_RUNPM_BOCO)
			adev->mp1_state = PP_MP1_STATE_NONE;
		return ret;
	}

Because switch_power_state is never reset on this error path, drm_open()
will explicitly reject new opens by returning -EINVAL. Does this mean a
failed runtime suspend renders the GPU completely unusable for new clients
until reboot?

[ ... ]
> @@ -2947,10 +2952,11 @@ static int amdgpu_pmops_runtime_resume(struct device *dev)
>  	if (!pci_device_is_present(adev->pdev))
>  		adev->no_hw_access = true;
>  
> -	if (adev->pm.rpm_mode == AMDGPU_RUNPM_PX) {
> +	if (adev->pm.rpm_mode == AMDGPU_RUNPM_PX ||
> +	    adev->pm.rpm_mode == AMDGPU_RUNPM_GMUX) {
>  		drm_dev->switch_power_state = DRM_SWITCH_POWER_CHANGING;

[Severity: High]
This is also a pre-existing issue, but the same state machine corruption can
occur during resume.

If either pci_enable_device() or amdgpu_device_resume() fails, the function
returns without resetting switch_power_state from DRM_SWITCH_POWER_CHANGING:

	ret = amdgpu_device_resume(drm_dev, false);
	if (ret) {
		if (adev->pm.rpm_mode == AMDGPU_RUNPM_PX ||
		    adev->pm.rpm_mode == AMDGPU_RUNPM_GMUX)
			pci_disable_device(pdev);
		return ret;
	}

Would it be safer to restore switch_power_state on these error paths so
that the state isn't permanently stuck?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=2