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Message-ID: <9742acac-9402-4351-8cff-559ba6536629@damsy.net>
Date: Wed, 5 Nov 2025 10:30:54 +0100
From: Pierre-Eric Pelloux-Prayer <pierre-eric@...sy.net>
To: Christian König <christian.koenig@....com>,
Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@....com>,
Alex Deucher <alexander.deucher@....com>, David Airlie <airlied@...il.com>,
Simona Vetter <simona@...ll.ch>, Sumit Semwal <sumit.semwal@...aro.org>
Cc: amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v1 17/20] drm/amdgpu: get rid of amdgpu_ttm_clear_buffer
Le 05/11/2025 à 09:46, Christian König a écrit :
>
>
> On 11/4/25 09:35, Pierre-Eric Pelloux-Prayer wrote:
>> It's doing the same thing as amdgpu_fill_buffer(src_data=0), so drop it.
>>
>> The only caveat is that amdgpu_res_cleared() return value is only valid
>> right after allocation.
>>
>> Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@....com>
>> ---
>> drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 9 +--
>> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 86 ++++------------------
>> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h | 3 -
>> 3 files changed, 18 insertions(+), 80 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> index 4a69324bb730..410e9b68ff81 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> @@ -723,15 +723,10 @@ int amdgpu_bo_create(struct amdgpu_device *adev,
>>
>> if (bp->flags & AMDGPU_GEM_CREATE_VRAM_CLEARED &&
>> bo->tbo.resource->mem_type == TTM_PL_VRAM) {
>> - struct dma_fence *fence;
>> -
>> - r = amdgpu_ttm_clear_buffer(bo, bo->tbo.base.resv, &fence);
>> + r = amdgpu_fill_buffer(NULL, bo, 0, NULL,
>> + NULL, AMDGPU_KERNEL_JOB_ID_TTM_CLEAR_BUFFER);
>> if (unlikely(r))
>> goto fail_unreserve;
>> -
>> - dma_resv_add_fence(bo->tbo.base.resv, fence,
>> - DMA_RESV_USAGE_KERNEL);
>> - dma_fence_put(fence);
>> }
>> if (!bp->resv)
>> amdgpu_bo_unreserve(bo);
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> index d88bdb2ac083..1f553c56f31d 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> @@ -2412,75 +2412,6 @@ static int amdgpu_ttm_fill_mem(struct amdgpu_ring *ring,
>> return 0;
>> }
>>
>> -/**
>> - * amdgpu_ttm_clear_buffer - clear memory buffers
>> - * @bo: amdgpu buffer object
>> - * @resv: reservation object
>> - * @fence: dma_fence associated with the operation
>> - *
>> - * Clear the memory buffer resource.
>> - *
>> - * Returns:
>> - * 0 for success or a negative error code on failure.
>> - */
>> -int amdgpu_ttm_clear_buffer(struct amdgpu_bo *bo,
>> - struct dma_resv *resv,
>> - struct dma_fence **fence)
>> -{
>> - struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
>> - struct amdgpu_ring *ring = adev->mman.buffer_funcs_rings[0];
>> - struct amdgpu_ttm_entity *entity;
>> - struct amdgpu_res_cursor cursor;
>> - u64 addr;
>> - int r = 0;
>> -
>> - if (!adev->mman.buffer_funcs_enabled)
>> - return -EINVAL;
>> -
>> - if (!fence)
>> - return -EINVAL;
>> - entity = &adev->mman.clear_entities[0];
>> - *fence = dma_fence_get_stub();
>> -
>> - amdgpu_res_first(bo->tbo.resource, 0, amdgpu_bo_size(bo), &cursor);
>> -
>> - mutex_lock(&entity->gart_window_lock);
>> - while (cursor.remaining) {
>> - struct dma_fence *next = NULL;
>> - u64 size;
>> -
>> - if (amdgpu_res_cleared(&cursor)) {
>> - amdgpu_res_next(&cursor, cursor.size);
>> - continue;
>> - }
>> -
>> - /* Never clear more than 256MiB at once to avoid timeouts */
>> - size = min(cursor.size, 256ULL << 20);
>> -
>> - r = amdgpu_ttm_map_buffer(&entity->base,
>> - &bo->tbo, bo->tbo.resource, &cursor,
>> - entity->gart_window_id1, ring, false, &size, &addr,
>> - NULL, NULL);
>> - if (r)
>> - goto err;
>> -
>> - r = amdgpu_ttm_fill_mem(ring, &entity->base, 0, addr, size, resv,
>> - &next, true,
>> - AMDGPU_KERNEL_JOB_ID_TTM_CLEAR_BUFFER);
>> - if (r)
>> - goto err;
>> -
>> - dma_fence_put(*fence);
>> - *fence = next;
>> -
>> - amdgpu_res_next(&cursor, size);
>> - }
>> -err:
>> - mutex_unlock(&entity->gart_window_lock);
>> -
>> - return r;
>> -}
>> -
>> /**
>> * amdgpu_fill_buffer - fill a buffer with a given value
>> * @entity: optional entity to use. If NULL, the clearing entities will be
>> @@ -2508,6 +2439,9 @@ int amdgpu_fill_buffer(struct amdgpu_ttm_entity *entity,
>> struct amdgpu_res_cursor dst;
>> uint64_t cur_size, to;
>> int r, e, n_fences;
>
>> + /* The clear flag is only valid directly after allocation. */
>> + bool consider_clear_flag =
>> + src_data == 0 && k_job_id == AMDGPU_KERNEL_JOB_ID_TTM_CLEAR_BUFFER;
>
> Absolutely clear NAK to that.
I suppose the NAK applies to the check, not the general idea of the patch?
In that case, would passing "bool consider_clear_flag" as a parameter be ok ?
Pierre-Eric
>
> Christian.
>
>>
>> /* The fences will be either added to the resv object or the last fence
>> * will be returned to the caller. In the latter case, all fill jobs will
>> @@ -2531,6 +2465,11 @@ int amdgpu_fill_buffer(struct amdgpu_ttm_entity *entity,
>> while (dst.remaining) {
>> cur_size = min(dst.size, 256ULL << 20);
>>
>> + if (consider_clear_flag && amdgpu_res_cleared(&dst)) {
>> + amdgpu_res_next(&dst, dst.size);
>> + continue;
>> + }
>> +
>> n_fences += 1;
>> amdgpu_res_next(&dst, cur_size);
>> }
>> @@ -2550,6 +2489,11 @@ int amdgpu_fill_buffer(struct amdgpu_ttm_entity *entity,
>> amdgpu_res_first(bo->tbo.resource, 0, amdgpu_bo_size(bo), &dst);
>>
>> while (dst.remaining) {
>> + if (consider_clear_flag && amdgpu_res_cleared(&dst)) {
>> + amdgpu_res_next(&dst, dst.size);
>> + continue;
>> + }
>> +
>> /* Never fill more than 256MiB at once to avoid timeouts */
>> cur_size = min(dst.size, 256ULL << 20);
>>
>> @@ -2574,8 +2518,10 @@ int amdgpu_fill_buffer(struct amdgpu_ttm_entity *entity,
>> goto error;
>> }
>>
>> +
>> r = amdgpu_ttm_fill_mem(ring, &entity->base,
>> - src_data, to, cur_size, resv,
>> + src_data, to, cur_size,
>> + resv,
>> &fence, true, k_job_id);
>> if (r) {
>> mutex_unlock(&entity->gart_window_lock);
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>> index c059a3d52b57..97e73919cb0c 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>> @@ -182,9 +182,6 @@ int amdgpu_copy_buffer(struct amdgpu_ring *ring,
>> struct dma_resv *resv,
>> struct dma_fence **fence,
>> bool vm_needs_flush, uint32_t copy_flags);
>> -int amdgpu_ttm_clear_buffer(struct amdgpu_bo *bo,
>> - struct dma_resv *resv,
>> - struct dma_fence **fence);
>> int amdgpu_fill_buffer(struct amdgpu_ttm_entity *entity,
>> struct amdgpu_bo *bo,
>> uint32_t src_data,
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