[PATCH 1/1] drm/amdgpu: Pin to gtt before cpu accesses dma buf.

Christian K├Ânig ckoenig.leichtzumerken at gmail.com
Wed Nov 29 09:38:33 UTC 2017


Am 29.11.2017 um 01:20 schrieb Samuel Li:
> To improve cpu read performance. This is implemented for APUs currently.

And once more a NAK for this approach.

What we could do is migrate the BO to GTT during mmap, but pinning it is 
out of question.

Regards,
Christian.

>
> Change-Id: I300a7daed8f2b0ba6be71a43196a6b8617ddc62e
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu.h               |   2 +
>   drivers/gpu/drm/amd/amdgpu/amdgpu_display.c       |  10 +-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c           |   2 +-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c         | 108 ++++++++++++++++++++++
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |   8 +-
>   5 files changed, 126 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index f8657c3..193db70 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -417,6 +417,8 @@ amdgpu_gem_prime_import_sg_table(struct drm_device *dev,
>   struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
>   					struct drm_gem_object *gobj,
>   					int flags);
> +struct drm_gem_object *amdgpu_gem_prime_import(struct drm_device *dev,
> +					    struct dma_buf *dma_buf);
>   int amdgpu_gem_prime_pin(struct drm_gem_object *obj);
>   void amdgpu_gem_prime_unpin(struct drm_gem_object *obj);
>   struct reservation_object *amdgpu_gem_prime_res_obj(struct drm_gem_object *);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> index d704a45..b5483e4 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> @@ -147,6 +147,7 @@ int amdgpu_crtc_page_flip_target(struct drm_crtc *crtc,
>   	struct drm_device *dev = crtc->dev;
>   	struct amdgpu_device *adev = dev->dev_private;
>   	struct amdgpu_crtc *amdgpu_crtc = to_amdgpu_crtc(crtc);
> +	bool gtt_scannable = (adev->asic_type >= CHIP_CARRIZO && adev->flags & AMD_IS_APU);
>   	struct amdgpu_framebuffer *old_amdgpu_fb;
>   	struct amdgpu_framebuffer *new_amdgpu_fb;
>   	struct drm_gem_object *obj;
> @@ -190,8 +191,13 @@ int amdgpu_crtc_page_flip_target(struct drm_crtc *crtc,
>   
>   	r = amdgpu_bo_pin(new_abo, AMDGPU_GEM_DOMAIN_VRAM, &base);
>   	if (unlikely(r != 0)) {
> -		DRM_ERROR("failed to pin new abo buffer before flip\n");
> -		goto unreserve;
> +		/* latest APUs support gtt scan out */
> +		if (gtt_scannable)
> +			r = amdgpu_bo_pin(new_abo, AMDGPU_GEM_DOMAIN_GTT, &base);
> +		if (unlikely(r != 0)) {
> +			DRM_ERROR("failed to pin new abo buffer before flip\n");
> +			goto unreserve;
> +		}
>   	}
>   
>   	r = reservation_object_get_fences_rcu(new_abo->tbo.resv, &work->excl,
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index 31383e0..df30b08 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -868,7 +868,7 @@ static struct drm_driver kms_driver = {
>   	.prime_handle_to_fd = drm_gem_prime_handle_to_fd,
>   	.prime_fd_to_handle = drm_gem_prime_fd_to_handle,
>   	.gem_prime_export = amdgpu_gem_prime_export,
> -	.gem_prime_import = drm_gem_prime_import,
> +	.gem_prime_import = amdgpu_gem_prime_import,
>   	.gem_prime_pin = amdgpu_gem_prime_pin,
>   	.gem_prime_unpin = amdgpu_gem_prime_unpin,
>   	.gem_prime_res_obj = amdgpu_gem_prime_res_obj,
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> index ae9c106..9e1424d 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> @@ -164,6 +164,82 @@ struct reservation_object *amdgpu_gem_prime_res_obj(struct drm_gem_object *obj)
>   	return bo->tbo.resv;
>   }
>   
> +static int amdgpu_gem_begin_cpu_access(struct dma_buf *dma_buf, enum dma_data_direction direction)
> +{
> +	struct amdgpu_bo *bo = gem_to_amdgpu_bo(dma_buf->priv);
> +	struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
> +	long i, ret = 0;
> +	unsigned old_count;
> +	bool reads = (direction == DMA_BIDIRECTIONAL || direction == DMA_FROM_DEVICE);
> +	bool gtt_scannable = (adev->asic_type >= CHIP_CARRIZO && adev->flags & AMD_IS_APU);
> +	u32 domain;
> +
> +	if (!reads || !gtt_scannable)
> +		return 0;
> +
> +	ret = amdgpu_bo_reserve(bo, false);
> +	if (unlikely(ret != 0))
> +		return ret;
> +
> +	/*
> +	 * Wait for all shared fences to complete before we switch to future
> +	 * use of exclusive fence on this prime shared bo.
> +	 */
> +	ret = reservation_object_wait_timeout_rcu(bo->tbo.resv, true, false,
> +						  MAX_SCHEDULE_TIMEOUT);
> +
> +	if (unlikely(ret < 0)) {
> +		DRM_DEBUG_PRIME("Fence wait failed: %li\n", ret);
> +		amdgpu_bo_unreserve(bo);
> +		return ret;
> +	}
> +
> +	ret = 0;
> +	/* Pin to gtt */
> +	domain = amdgpu_mem_type_to_domain(bo->tbo.mem.mem_type);
> +	if (domain == AMDGPU_GEM_DOMAIN_VRAM) {
> +		old_count = bo->pin_count;
> +		for (i = 0; i < old_count; i++)
> +			amdgpu_bo_unpin(bo);
> +		for (i = 0; i < old_count; i++) {
> +			ret = amdgpu_bo_pin(bo, AMDGPU_GEM_DOMAIN_GTT, NULL);
> +			if (unlikely(ret != 0))
> +				break;
> +		}
> +	}
> +	if (ret == 0)
> +		ret = amdgpu_bo_pin(bo, AMDGPU_GEM_DOMAIN_GTT, NULL);
> +
> +	amdgpu_bo_unreserve(bo);
> +	return ret;
> +}
> +
> +static int amdgpu_gem_end_cpu_access(struct dma_buf *dma_buf, enum dma_data_direction direction)
> +{
> +	struct amdgpu_bo *bo = gem_to_amdgpu_bo(dma_buf->priv);
> +	int ret = 0;
> +	bool reads = (direction == DMA_BIDIRECTIONAL || direction == DMA_FROM_DEVICE);
> +	struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
> +	bool gtt_scannable = (adev->asic_type >= CHIP_CARRIZO && adev->flags & AMD_IS_APU);
> +
> +	if (!reads || !gtt_scannable)
> +		return 0;
> +
> +	mb();
> +	ret = amdgpu_bo_reserve(bo, true);
> +	if (unlikely(ret != 0))
> +		return ret;
> +
> +	amdgpu_bo_unpin(bo);
> +
> +	amdgpu_bo_unreserve(bo);
> +
> +	return 0;
> +}
> +
> +static struct dma_buf_ops amdgpu_dmabuf_ops;
> +static atomic_t aops_lock;
> +
>   struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
>   					struct drm_gem_object *gobj,
>   					int flags)
> @@ -178,5 +254,37 @@ struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
>   	buf = drm_gem_prime_export(dev, gobj, flags);
>   	if (!IS_ERR(buf))
>   		buf->file->f_mapping = dev->anon_inode->i_mapping;
> +
> +	while (amdgpu_dmabuf_ops.begin_cpu_access != amdgpu_gem_begin_cpu_access ||
> +		amdgpu_dmabuf_ops.end_cpu_access != amdgpu_gem_end_cpu_access )
> +	{
> +		if (!atomic_cmpxchg(&aops_lock, 0, 1)) {
> +			amdgpu_dmabuf_ops = *(buf->ops);
> +			amdgpu_dmabuf_ops.begin_cpu_access = amdgpu_gem_begin_cpu_access;
> +			amdgpu_dmabuf_ops.end_cpu_access = amdgpu_gem_end_cpu_access;
> +		}
> +	}
> +	buf->ops = &amdgpu_dmabuf_ops;
> +
>   	return buf;
>   }
> +
> +struct drm_gem_object *amdgpu_gem_prime_import(struct drm_device *dev,
> +					    struct dma_buf *dma_buf)
> +{
> +	struct drm_gem_object *obj;
> +
> +	if (dma_buf->ops == &amdgpu_dmabuf_ops) {
> +		obj = dma_buf->priv;
> +		if (obj->dev == dev) {
> +			/*
> +			 * Importing dmabuf exported from out own gem increases
> +			 * refcount on gem itself instead of f_count of dmabuf.
> +			 */
> +			drm_gem_object_get(obj);
> +			return obj;
> +		}
> +	}
> +
> +	return drm_gem_prime_import(dev, dma_buf);
> + }
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index a3bf021..f25b830 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -2987,6 +2987,8 @@ static int dm_plane_helper_prepare_fb(struct drm_plane *plane,
>   	int r;
>   	struct dm_plane_state *dm_plane_state_new, *dm_plane_state_old;
>   	unsigned int awidth;
> +	struct amdgpu_device *adev = plane->dev->dev_private;
> +	bool gtt_scannable = (adev->asic_type >= CHIP_CARRIZO && adev->flags & AMD_IS_APU);
>   
>   	dm_plane_state_old = to_dm_plane_state(plane->state);
>   	dm_plane_state_new = to_dm_plane_state(new_state);
> @@ -3005,7 +3007,11 @@ static int dm_plane_helper_prepare_fb(struct drm_plane *plane,
>   		return r;
>   
>   	r = amdgpu_bo_pin(rbo, AMDGPU_GEM_DOMAIN_VRAM, &afb->address);
> -
> +	if (unlikely(r != 0)) {
> +		/* latest APUs support gtt scan out */
> +		if (gtt_scannable)
> +			r = amdgpu_bo_pin(rbo, AMDGPU_GEM_DOMAIN_GTT, &afb->address);
> +	}
>   
>   	amdgpu_bo_unreserve(rbo);
>   



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