Message-ID: <3698448.dWV9SEqChM@timur-hyperion>
Date: Fri, 23 Jan 2026 12:16:15 +0100
From: Timur Kristóf <timur.kristof@...il.com>
To: Alex Deucher <alexander.deucher@....com>,
 Christian König <christian.koenig@....com>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 amd-gfx@...ts.freedesktop.org
Cc: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@....com>,
 amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org,
 Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@....com>
Subject:
 Re: [PATCH v5 04/10] drm/amdgpu: remove AMDGPU_GTT_NUM_TRANSFER_WINDOWS

On Thursday, January 22, 2026 6:02:01 PM Central European Standard Time 
Pierre-Eric Pelloux-Prayer wrote:
> Instead use amdgpu_gtt_mgr_alloc_entries to avoid hardcoding
> the number of windows we need.
> 
> It also allows to simplify amdgpu_gtt_mgr_init because we don't
> need to reserve some pages anymore and this makes the
> amdgpu_vce_required_gart_pages function unneeded.

I suggest to split this patch into two if possible in order to make it cleaner 
and also allow for easier bisection in the future:
1. First patch to remove amdgpu_vce_required_gart_pages() and use
the amdgpu_gtt_mgr_alloc_entries() function instead.
2. Second patch to get rid of AMDGPU_GTT_NUM_TRANSFER_WINDOWS

> 
> ---
> v5: switch to amdgpu_gtt_mgr_alloc_entries
> ---
> 
> Signed-off-by: Pierre-Eric Pelloux-Prayer
> <pierre-eric.pelloux-prayer@....com> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c |  6 +-
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c     | 66 +++++++++++++--------
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h     |  2 +-
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c     | 18 ------
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vce.h     |  2 +-
>  drivers/gpu/drm/amd/amdgpu/vce_v1_0.c       | 27 ++++++---
>  6 files changed, 63 insertions(+), 58 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c index
> dd9b845d5783..9b0bcf6aca44 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
> @@ -324,17 +324,13 @@ int amdgpu_gtt_mgr_init(struct amdgpu_device *adev,
> uint64_t gtt_size) {
>  	struct amdgpu_gtt_mgr *mgr = &adev->mman.gtt_mgr;
>  	struct ttm_resource_manager *man = &mgr->manager;
> -	uint64_t start, size;
> 
>  	man->use_tt = true;
>  	man->func = &amdgpu_gtt_mgr_func;
> 
>  	ttm_resource_manager_init(man, &adev->mman.bdev, gtt_size);
> 
> -	start = AMDGPU_GTT_MAX_TRANSFER_SIZE * 
AMDGPU_GTT_NUM_TRANSFER_WINDOWS;
> -	start += amdgpu_vce_required_gart_pages(adev);
> -	size = (adev->gmc.gart_size >> PAGE_SHIFT) - start;
> -	drm_mm_init(&mgr->mm, start, size);
> +	drm_mm_init(&mgr->mm, 0, adev->gmc.gart_size >> PAGE_SHIFT);
>  	spin_lock_init(&mgr->lock);
> 
>  	ttm_set_driver_manager(&adev->mman.bdev, TTM_PL_TT, &mgr-
>manager);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c index 8b38b5ed9a9c..d23d3046919b
> 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -2012,37 +2012,47 @@ static void amdgpu_ttm_free_mmio_remap_bo(struct
> amdgpu_device *adev) adev->rmmio_remap.bo = NULL;
>  }
> 
> -static int amdgpu_ttm_buffer_entity_init(struct amdgpu_ttm_buffer_entity
> *entity, +static int amdgpu_ttm_buffer_entity_init(struct amdgpu_gtt_mgr
> *mgr, +					 struct 
amdgpu_ttm_buffer_entity *entity,
>  					 enum 
drm_sched_priority prio,
>  					 struct 
drm_gpu_scheduler **scheds,
>  					 int num_schedulers,
> -					 int 
starting_gart_window,
>  					 u32 num_gart_windows)
>  {
> -	int i, r;
> +	int i, r, num_pages;
> 
>  	r = drm_sched_entity_init(&entity->base, prio, scheds, 
num_schedulers,
> NULL); if (r)
>  		return r;
> 
> -
>  	mutex_init(&entity->lock);
> 
>  	if (ARRAY_SIZE(entity->gart_window_offs) < num_gart_windows)
> -		return starting_gart_window;
> +		return -EINVAL;
> +	if (num_gart_windows == 0)
> +		return 0;
> +
> +	num_pages = num_gart_windows * AMDGPU_GTT_MAX_TRANSFER_SIZE;
> +	r = amdgpu_gtt_mgr_alloc_entries(mgr, &entity->node, num_pages,
> +					 DRM_MM_INSERT_BEST);
> +	if (r) {
> +		drm_sched_entity_destroy(&entity->base);
> +		return r;
> +	}
> 
>  	for (i = 0; i < num_gart_windows; i++) {
>  		entity->gart_window_offs[i] =
> -			(u64)starting_gart_window * 
AMDGPU_GTT_MAX_TRANSFER_SIZE *
> -				AMDGPU_GPU_PAGE_SIZE;
> -		starting_gart_window++;
> +			(entity->node.start + (u64)i * 
AMDGPU_GTT_MAX_TRANSFER_SIZE) *
> +			AMDGPU_GPU_PAGE_SIZE;
>  	}
> 
> -	return starting_gart_window;
> +	return 0;
>  }
> 
> -static void amdgpu_ttm_buffer_entity_fini(struct amdgpu_ttm_buffer_entity
> *entity) +static void amdgpu_ttm_buffer_entity_fini(struct amdgpu_gtt_mgr
> *mgr, +					  struct 
amdgpu_ttm_buffer_entity *entity)
>  {
> +	amdgpu_gtt_mgr_free_entries(mgr, &entity->node);
>  	drm_sched_entity_destroy(&entity->base);
>  }
> 
> @@ -2343,36 +2353,42 @@ void amdgpu_ttm_set_buffer_funcs_status(struct
> amdgpu_device *adev, bool enable)
> 
>  		ring = adev->mman.buffer_funcs_ring;
>  		sched = &ring->sched;
> -		r = amdgpu_ttm_buffer_entity_init(&adev-
>mman.default_entity,
> -						  
DRM_SCHED_PRIORITY_KERNEL, &sched, 1,
> -						  0, 0);
> +		r = amdgpu_ttm_buffer_entity_init(&adev->mman.gtt_mgr,
> +						  &adev-
>mman.default_entity,
> +						  
DRM_SCHED_PRIORITY_KERNEL,
> +						  &sched, 1, 
0);
>  		if (r < 0) {
>  			dev_err(adev->dev,
>  				"Failed setting up TTM entity 
(%d)\n", r);
>  			return;
>  		}
> 
> -		r = amdgpu_ttm_buffer_entity_init(&adev-
>mman.clear_entity,
> -						  
DRM_SCHED_PRIORITY_NORMAL, &sched, 1,
> -						  r, 1);
> +		r = amdgpu_ttm_buffer_entity_init(&adev->mman.gtt_mgr,
> +						  &adev-
>mman.clear_entity,
> +						  
DRM_SCHED_PRIORITY_NORMAL,
> +						  &sched, 1, 
1);
>  		if (r < 0) {
>  			dev_err(adev->dev,
>  				"Failed setting up TTM BO clear 
entity (%d)\n", r);
>  			goto error_free_default_entity;
>  		}
> 
> -		r = amdgpu_ttm_buffer_entity_init(&adev-
>mman.move_entity,
> -						  
DRM_SCHED_PRIORITY_NORMAL, &sched, 1,
> -						  r, 2);
> +		r = amdgpu_ttm_buffer_entity_init(&adev->mman.gtt_mgr,
> +						  &adev-
>mman.move_entity,
> +						  
DRM_SCHED_PRIORITY_NORMAL,
> +						  &sched, 1, 
2);
>  		if (r < 0) {
>  			dev_err(adev->dev,
>  				"Failed setting up TTM BO move 
entity (%d)\n", r);
>  			goto error_free_clear_entity;
>  		}
>  	} else {
> -		amdgpu_ttm_buffer_entity_fini(&adev-
>mman.default_entity);
> -		amdgpu_ttm_buffer_entity_fini(&adev->mman.clear_entity);
> -		amdgpu_ttm_buffer_entity_fini(&adev->mman.move_entity);
> +		amdgpu_ttm_buffer_entity_fini(&adev->mman.gtt_mgr,
> +					      &adev-
>mman.default_entity);
> +		amdgpu_ttm_buffer_entity_fini(&adev->mman.gtt_mgr,
> +					      &adev-
>mman.clear_entity);
> +		amdgpu_ttm_buffer_entity_fini(&adev->mman.gtt_mgr,
> +					      &adev-
>mman.move_entity);
>  		/* Drop all the old fences since re-creating the 
scheduler entities
>  		 * will allocate new contexts.
>  		 */
> @@ -2390,9 +2406,11 @@ void amdgpu_ttm_set_buffer_funcs_status(struct
> amdgpu_device *adev, bool enable) return;
> 
>  error_free_clear_entity:
> -	amdgpu_ttm_buffer_entity_fini(&adev->mman.clear_entity);
> +	amdgpu_ttm_buffer_entity_fini(&adev->mman.gtt_mgr,
> +				      &adev->mman.clear_entity);
>  error_free_default_entity:
> -	amdgpu_ttm_buffer_entity_fini(&adev->mman.default_entity);
> +	amdgpu_ttm_buffer_entity_fini(&adev->mman.gtt_mgr,
> +				      &adev->mman.default_entity);
>  }
> 
>  static int amdgpu_ttm_prepare_job(struct amdgpu_device *adev,
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h index 871388b86503..c8284cb2d22c
> 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
> @@ -40,7 +40,6 @@
>  #define __AMDGPU_PL_NUM	(TTM_PL_PRIV + 6)
> 
>  #define AMDGPU_GTT_MAX_TRANSFER_SIZE	512
> -#define AMDGPU_GTT_NUM_TRANSFER_WINDOWS	3
> 
>  extern const struct attribute_group amdgpu_vram_mgr_attr_group;
>  extern const struct attribute_group amdgpu_gtt_mgr_attr_group;
> @@ -56,6 +55,7 @@ struct amdgpu_gtt_mgr {
>  struct amdgpu_ttm_buffer_entity {
>  	struct drm_sched_entity base;
>  	struct mutex		lock;
> +	struct drm_mm_node	node;
>  	u64			gart_window_offs[2];
>  };
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c index a7d8f1ce6ac2..eb4a15db2ef2
> 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c
> @@ -450,24 +450,6 @@ void amdgpu_vce_free_handles(struct amdgpu_device
> *adev, struct drm_file *filp) }
>  }
> 
> -/**
> - * amdgpu_vce_required_gart_pages() - gets number of GART pages required by
> VCE - *
> - * @adev: amdgpu_device pointer
> - *
> - * Returns how many GART pages we need before GTT for the VCE IP block.
> - * For VCE1, see vce_v1_0_ensure_vcpu_bo_32bit_addr for details.
> - * For VCE2+, this is not needed so return zero.
> - */
> -u32 amdgpu_vce_required_gart_pages(struct amdgpu_device *adev)
> -{
> -	/* VCE IP block not added yet, so can't use amdgpu_ip_version */
> -	if (adev->family == AMDGPU_FAMILY_SI)
> -		return 512;
> -
> -	return 0;
> -}
> -
>  /**
>   * amdgpu_vce_get_create_msg - generate a VCE create msg
>   *
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.h
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.h index 1c3464ce5037..a59d87e09004
> 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.h
> @@ -52,6 +52,7 @@ struct amdgpu_vce {
>  	uint32_t                srbm_soft_reset;
>  	unsigned		num_rings;
>  	uint32_t		keyselect;
> +	struct drm_mm_node	node;
>  };
> 
>  int amdgpu_vce_early_init(struct amdgpu_device *adev);
> @@ -61,7 +62,6 @@ int amdgpu_vce_entity_init(struct amdgpu_device *adev,
> struct amdgpu_ring *ring) int amdgpu_vce_suspend(struct amdgpu_device
> *adev);
>  int amdgpu_vce_resume(struct amdgpu_device *adev);
>  void amdgpu_vce_free_handles(struct amdgpu_device *adev, struct drm_file
> *filp); -u32 amdgpu_vce_required_gart_pages(struct amdgpu_device *adev);
>  int amdgpu_vce_ring_parse_cs(struct amdgpu_cs_parser *p, struct amdgpu_job
> *job, struct amdgpu_ib *ib);
>  int amdgpu_vce_ring_parse_cs_vm(struct amdgpu_cs_parser *p,
> diff --git a/drivers/gpu/drm/amd/amdgpu/vce_v1_0.c
> b/drivers/gpu/drm/amd/amdgpu/vce_v1_0.c index 9ae424618556..bd47fda52e7e
> 100644
> --- a/drivers/gpu/drm/amd/amdgpu/vce_v1_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/vce_v1_0.c
> @@ -47,11 +47,6 @@
>  #define VCE_V1_0_DATA_SIZE	(7808 * (AMDGPU_MAX_VCE_HANDLES + 1))
>  #define VCE_STATUS_VCPU_REPORT_FW_LOADED_MASK	0x02
> 
> -#define VCE_V1_0_GART_PAGE_START \
> -	(AMDGPU_GTT_MAX_TRANSFER_SIZE * AMDGPU_GTT_NUM_TRANSFER_WINDOWS)
> -#define VCE_V1_0_GART_ADDR_START \
> -	(VCE_V1_0_GART_PAGE_START * AMDGPU_GPU_PAGE_SIZE)
> -
>  static void vce_v1_0_set_ring_funcs(struct amdgpu_device *adev);
>  static void vce_v1_0_set_irq_funcs(struct amdgpu_device *adev);
> 
> @@ -541,6 +536,16 @@ static int vce_v1_0_ensure_vcpu_bo_32bit_addr(struct
> amdgpu_device *adev) u64 num_pages = ALIGN(bo_size, AMDGPU_GPU_PAGE_SIZE) /
> AMDGPU_GPU_PAGE_SIZE; u64 pa = amdgpu_gmc_vram_pa(adev, adev->vce.vcpu_bo);
>  	u64 flags = AMDGPU_PTE_READABLE | AMDGPU_PTE_WRITEABLE | 
AMDGPU_PTE_VALID;
> +	u64 vce_gart_start;
> +	int r;
> +
> +	r = amdgpu_gtt_mgr_alloc_entries(&adev->mman.gtt_mgr,
> +					 &adev->vce.node, 
num_pages,
> +					 DRM_MM_INSERT_LOW);
> +	if (r)
> +		return r;
> +
> +	vce_gart_start = adev->vce.node.start * AMDGPU_GPU_PAGE_SIZE;

When the VCPU BO already has a 32-bit address, VCE does not need to use any 
GART space at all. I think you can just safely remove the "Check if the VCPU 
BO already has a 32-bit address". That is practically never going to be case 
anyway.

> 
>  	/*
>  	 * Check if the VCPU BO already has a 32-bit address.
> @@ -550,12 +555,12 @@ static int vce_v1_0_ensure_vcpu_bo_32bit_addr(struct
> amdgpu_device *adev) return 0;
> 
>  	/* Check if we can map the VCPU BO in GART to a 32-bit address. */
> -	if (adev->gmc.gart_start + VCE_V1_0_GART_ADDR_START > 
max_vcpu_bo_addr)
> +	if (adev->gmc.gart_start + vce_gart_start > max_vcpu_bo_addr)
>  		return -EINVAL;
> 
> -	amdgpu_gart_map_vram_range(adev, pa, VCE_V1_0_GART_PAGE_START,
> +	amdgpu_gart_map_vram_range(adev, pa, adev->vce.node.start,
>  				   num_pages, flags, adev-
>gart.ptr);
> -	adev->vce.gpu_addr = adev->gmc.gart_start + 
VCE_V1_0_GART_ADDR_START;
> +	adev->vce.gpu_addr = adev->gmc.gart_start + vce_gart_start;
>  	if (adev->vce.gpu_addr > max_vcpu_bo_addr)
>  		return -EINVAL;
> 
> @@ -610,7 +615,11 @@ static int vce_v1_0_sw_fini(struct amdgpu_ip_block
> *ip_block) if (r)
>  		return r;
> 
> -	return amdgpu_vce_sw_fini(adev);
> +	r = amdgpu_vce_sw_fini(adev);
> +
> +	amdgpu_gtt_mgr_free_entries(&adev->mman.gtt_mgr, &adev->vce.node);
> +
> +	return r;
>  }
> 
>  /**

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