[PATCH 2/3] drm/amd: Use runtime suspend in lieu regular suspend on supported dGPUs

[Lazar, Lijo]

On 2/21/2023 1:46 AM, Mario Limonciello wrote:
> The PMFW on dGPUs that support BACO will transition them in and out
> of BACO when video/audio move in out of D3/D0.
> 
> On the Linux side users can configure what sleep mode to use in
> `/sys/power/mem_sleep`, but if the host hardware doesn't cut the
> power rails during this state then calling suspend from Linux may
> cause a mismatch of behavior.
> 
> To avoid this, only run the runtime suspend and resume callbacks
> when the dGPU supports BACO or BOCO and the smart flags didn't return
> to skip these stages (because already runtime suspended).
> 
> Cc: Peter Kopec <pekopec at redhat.com>
> Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index c3d3a042946d..fdc1cbf8ad10 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -2418,8 +2418,11 @@ static int amdgpu_pmops_suspend(struct device *dev)
>   		adev->in_s0ix = true;
>   	else if (amdgpu_acpi_is_s3_active(adev))
>   		adev->in_s3 = true;
> -	if (!adev->in_s0ix && !adev->in_s3)
> +	if (!adev->in_s0ix && !adev->in_s3) {
> +		pm_runtime_mark_last_busy(dev);
> +		pm_runtime_autosuspend(dev);

This is asking the device to be suspended (from a suspend call and that 
sounds weird).  Runtime pm handler will assume D3cold scenario and 
explicitly request BACO entry. Wondering what would happen if the 
platform doesn't put it in D3cold under s2Idle for dGPUs (BACO/BOCO).

Thanks,
Lijo

>   		return 0;
> +	}
>   	return amdgpu_device_suspend(drm_dev, true);
>   }
>   
> @@ -2440,8 +2443,10 @@ static int amdgpu_pmops_resume(struct device *dev)
>   	struct amdgpu_device *adev = drm_to_adev(drm_dev);
>   	int r;
>   
> -	if (!adev->in_s0ix && !adev->in_s3)
> +	if (!adev->in_s0ix && !adev->in_s3) {
> +		pm_runtime_resume(dev);
>   		return 0;
> +	}
>   
>   	/* Avoids registers access if device is physically gone */
>   	if (!pci_device_is_present(adev->pdev))