[PATCH] drm/amd: Add Suspend/Hibernate notification callback support

[Mario Limonciello]

On 11/18/2024 14:03, Mario Limonciello wrote:
> As part of the suspend sequence VRAM needs to be evicted on dGPUs.
> In order to make suspend/resume more reliable we moved this into
> the pmops prepare() callback so that the suspend sequence would fail
> but the system could remain operational under high memory usage suspend.
> 
> Another class of issues exist though where due to memory fragementation
> there isn't a large enough contiguous space and swap isn't accessible.
> 
> Add support for a suspend/hibernate notification callback that could
> evict VRAM before tasks are frozen. This should allow paging out to swap
> if necessary.
> 
> Link: https://github.com/ROCm/ROCK-Kernel-Driver/issues/174
> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/3476
> Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>

This patch has some very good feedback on helping this memory pressure 
issue.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/2362

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu.h        |  1 +
>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 36 ++++++++++++++++++++++
>   2 files changed, 37 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index a37e687acbbc5..e70ca85151046 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -885,6 +885,7 @@ struct amdgpu_device {
>   	bool				need_swiotlb;
>   	bool				accel_working;
>   	struct notifier_block		acpi_nb;
> +	struct notifier_block		pm_nb;
>   	struct amdgpu_i2c_chan		*i2c_bus[AMDGPU_MAX_I2C_BUS];
>   	struct debugfs_blob_wrapper     debugfs_vbios_blob;
>   	struct debugfs_blob_wrapper     debugfs_discovery_blob;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index b3ca911e55d61..5a4e9c7daf895 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -190,6 +190,8 @@ void amdgpu_set_init_level(struct amdgpu_device *adev,
>   }
>   
>   static inline void amdgpu_device_stop_pending_resets(struct amdgpu_device *adev);
> +static int amdgpu_device_pm_notifier(struct notifier_block *nb, unsigned long mode,
> +				     void *data);
>   
>   /**
>    * DOC: pcie_replay_count
> @@ -4582,6 +4584,11 @@ int amdgpu_device_init(struct amdgpu_device *adev,
>   
>   	amdgpu_device_check_iommu_direct_map(adev);
>   
> +	adev->pm_nb.notifier_call = amdgpu_device_pm_notifier;
> +	r = register_pm_notifier(&adev->pm_nb);
> +	if (r)
> +		goto failed;
> +
>   	return 0;
>   
>   release_ras_con:
> @@ -4646,6 +4653,8 @@ void amdgpu_device_fini_hw(struct amdgpu_device *adev)
>   		drain_workqueue(adev->mman.bdev.wq);
>   	adev->shutdown = true;
>   
> +	unregister_pm_notifier(&adev->pm_nb);
> +
>   	/* make sure IB test finished before entering exclusive mode
>   	 * to avoid preemption on IB test
>   	 */
> @@ -4777,6 +4786,33 @@ static int amdgpu_device_evict_resources(struct amdgpu_device *adev)
>   /*
>    * Suspend & resume.
>    */
> +/**
> + * amdgpu_device_pm_notifier - Notification block for Suspend/Hibernate events
> + * @nb: notifier block
> + * @mode: suspend mode
> + * @data: data
> + *
> + * This function is called when the system is about to suspend or hibernate.
> + * It is used to evict resources from the device before the system goes to
> + * sleep while there is still access to swap.
> + *
> + */
> +static int amdgpu_device_pm_notifier(struct notifier_block *nb, unsigned long mode,
> +				     void *data)
> +{
> +	struct amdgpu_device *adev = container_of(nb, struct amdgpu_device, pm_nb);
> +
> +	switch (mode) {
> +	case PM_HIBERNATION_PREPARE:
> +	case PM_SUSPEND_PREPARE:
> +		if (amdgpu_device_evict_resources(adev))
> +			return NOTIFY_BAD;
> +		break;
> +	}
> +
> +	return NOTIFY_DONE;
> +}
> +
>   /**
>    * amdgpu_device_prepare - prepare for device suspend
>    *