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Message-ID: <9d3fb5f6-6e54-46e0-9b49-23bce4f4bfd9@amd.com>
Date: Wed, 5 Nov 2025 11:07:32 +0100
From: Christian König <christian.koenig@....com>
To: Pierre-Eric Pelloux-Prayer <pierre-eric@...sy.net>,
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
On 11/5/25 10:30, Pierre-Eric Pelloux-Prayer wrote:
>
>
> 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?
Correct.
> In that case, would passing "bool consider_clear_flag" as a parameter be ok ?
And then determining the k_job_id based on this new flag? Yeah, that sounds much cleaner.
Christian.
>
> 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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