linux-kernel - Re: [PATCH v3 1/5] drm/ttm: add new api ttm_device_prepare

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Message-ID: <f5562f2b-1055-4ce1-817a-d51a996a2418@amd.com>
Date: Tue, 8 Jul 2025 10:38:48 +0200
From: Christian König <christian.koenig@....com>
To: Samuel Zhang <guoqing.zhang@....com>, alexander.deucher@....com,
 rafael@...nel.org, len.brown@...el.com, pavel@...nel.org,
 gregkh@...uxfoundation.org, dakr@...nel.org, airlied@...il.com,
 simona@...ll.ch, ray.huang@....com, matthew.auld@...el.com,
 matthew.brost@...el.com, maarten.lankhorst@...ux.intel.com,
 mripard@...nel.org, tzimmermann@...e.de
Cc: mario.limonciello@....com, lijo.lazar@....com, victor.zhao@....com,
 haijun.chang@....com, Qing.Ma@....com, Owen.Zhang2@....com,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v3 1/5] drm/ttm: add new api
 ttm_device_prepare_hibernation()



On 08.07.25 09:42, Samuel Zhang wrote:
> This new api is used for hibernation to move GTT BOs to shmem after
> VRAM eviction. shmem will be flushed to swap disk later to reduce
> the system memory usage for hibernation.
> 
> Signed-off-by: Samuel Zhang <guoqing.zhang@....com>
> ---
>  drivers/gpu/drm/ttm/ttm_device.c | 22 ++++++++++++++++++++++
>  include/drm/ttm/ttm_device.h     |  1 +
>  2 files changed, 23 insertions(+)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
> index 02e797fd1891..f14437ea0cce 100644
> --- a/drivers/gpu/drm/ttm/ttm_device.c
> +++ b/drivers/gpu/drm/ttm/ttm_device.c
> @@ -123,6 +123,28 @@ static int ttm_global_init(void)
>  	return ret;
>  }
>  
> +/**
> + * move GTT BOs to shmem for hibernation.

That is not the correct kerneldoc style.

Please make sure that for example make htmldocs doesn't throw any new warning.

> + *
> + * returns 0 on success, negative on failure.
> + */
> +int ttm_device_prepare_hibernation(struct ttm_device *bdev)
> +{
> +	struct ttm_operation_ctx ctx = {
> +		.interruptible = false,
> +		.no_wait_gpu = false,
> +		.force_alloc = true
> +	};
> +	int ret;
> +

> +	guard(mutex)(&ttm_global_mutex);

That is unnecessary now, the function doesn't touch the device list any more.

Regards,
Christian.

> +	do {
> +		ret = ttm_device_swapout(bdev, &ctx, GFP_KERNEL);
> +	} while (ret > 0);
> +	return ret;
> +}
> +EXPORT_SYMBOL(ttm_device_prepare_hibernation);
> +
>  /*
>   * A buffer object shrink method that tries to swap out the first
>   * buffer object on the global::swap_lru list.
> diff --git a/include/drm/ttm/ttm_device.h b/include/drm/ttm/ttm_device.h
> index 39b8636b1845..592b5f802859 100644
> --- a/include/drm/ttm/ttm_device.h
> +++ b/include/drm/ttm/ttm_device.h
> @@ -272,6 +272,7 @@ struct ttm_device {
>  int ttm_global_swapout(struct ttm_operation_ctx *ctx, gfp_t gfp_flags);
>  int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
>  		       gfp_t gfp_flags);
> +int ttm_device_prepare_hibernation(struct ttm_device *bdev);
>  
>  static inline struct ttm_resource_manager *
>  ttm_manager_type(struct ttm_device *bdev, int mem_type)