Commit f5b8794e authored by Mikko Perttunen's avatar Mikko Perttunen Committed by Thierry Reding
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drm/tegra: gem: Don't attach dma-bufs when not needed 



The dma-buf import code currently attaches and maps all imported
dma-bufs to the drm device to get their sgt for mapping to the
directly managed IOMMU domain.

In many cases, like for newer chips (Tegra186+), the directly
managed IOMMU domain is, however, not used. Mapping to the drm
device can also cause issues e.g. with swiotlb since it is not
a real device.

To improve the situation, only attach and map imported dma-bufs
when required.

Signed-off-by: default avatarMikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: default avatarThierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240424051335.2872574-2-cyndis@kapsi.fi
parent 4ed09565

drivers/gpu/drm/tegra/gem.c

+36 −30
Original line number Diff line number Diff line
@@ -76,8 +76,8 @@ static struct host1x_bo_mapping *tegra_bo_pin(struct device *dev, struct host1x_ 
	/*

	 * Imported buffers need special treatment to satisfy the semantics of DMA-BUF.

	 */

	if (gem->import_attach) {

		struct dma_buf *buf = gem->import_attach->dmabuf;

	if (obj->dma_buf) {

		struct dma_buf *buf = obj->dma_buf;



		map->attach = dma_buf_attach(buf, dev);

		if (IS_ERR(map->attach)) {
@@ -184,8 +184,8 @@ static void *tegra_bo_mmap(struct host1x_bo *bo) 
	if (obj->vaddr)

		return obj->vaddr;



	if (obj->gem.import_attach) {

		ret = dma_buf_vmap_unlocked(obj->gem.import_attach->dmabuf, &map);

	if (obj->dma_buf) {

		ret = dma_buf_vmap_unlocked(obj->dma_buf, &map);

		if (ret < 0)

			return ERR_PTR(ret);
@@ -208,8 +208,8 @@ static void tegra_bo_munmap(struct host1x_bo *bo, void *addr) 
	if (obj->vaddr)

		return;



	if (obj->gem.import_attach)

		return dma_buf_vunmap_unlocked(obj->gem.import_attach->dmabuf, &map);

	if (obj->dma_buf)

		return dma_buf_vunmap_unlocked(obj->dma_buf, &map);



	vunmap(addr);

}
@@ -465,27 +465,32 @@ static struct tegra_bo *tegra_bo_import(struct drm_device *drm, 
	if (IS_ERR(bo))

		return bo;



	/*

	 * If we need to use IOMMU API to map the dma-buf into the internally managed

	 * domain, map it first to the DRM device to get an sgt.

	 */

	if (tegra->domain) {

		attach = dma_buf_attach(buf, drm->dev);

		if (IS_ERR(attach)) {

			err = PTR_ERR(attach);

			goto free;

		}



	get_dma_buf(buf);



		bo->sgt = dma_buf_map_attachment_unlocked(attach, DMA_TO_DEVICE);

		if (IS_ERR(bo->sgt)) {

			err = PTR_ERR(bo->sgt);

			goto detach;

		}



	if (tegra->domain) {

		err = tegra_bo_iommu_map(tegra, bo);

		if (err < 0)

			goto detach;

	}



		bo->gem.import_attach = attach;

	}



	get_dma_buf(buf);

	bo->dma_buf = buf;



	return bo;
@@ -516,19 +521,20 @@ void tegra_bo_free_object(struct drm_gem_object *gem) 
				dev_name(mapping->dev));

	}



	if (tegra->domain)

	if (tegra->domain) {

		tegra_bo_iommu_unmap(tegra, bo);



		if (gem->import_attach) {

		struct dma_buf *dmabuf = gem->import_attach->dmabuf;



			dma_buf_unmap_attachment_unlocked(gem->import_attach, bo->sgt,

							  DMA_TO_DEVICE);

		dma_buf_detach(dmabuf, gem->import_attach);

		dma_buf_put(dmabuf);

	} else {

		tegra_bo_free(gem->dev, bo);

			dma_buf_detach(gem->import_attach->dmabuf, gem->import_attach);

		}

	}



	tegra_bo_free(gem->dev, bo);



	if (bo->dma_buf)

		dma_buf_put(bo->dma_buf);



	drm_gem_object_release(gem);

	kfree(bo);

drivers/gpu/drm/tegra/gem.h

+21 −0
Original line number Diff line number Diff line
@@ -32,6 +32,26 @@ struct tegra_bo_tiling { 
	enum tegra_bo_sector_layout sector_layout;

};



/*

 * How memory is referenced within a tegra_bo:

 *

 * Buffer source  | Mapping API(*)  | Fields

 * ---------------+-----------------+---------------

 * Allocated here | DMA API         | iova (IOVA mapped to drm->dev), vaddr (CPU VA)

 *

 * Allocated here | IOMMU API       | pages/num_pages (Phys. memory), sgt (Mapped to drm->dev),

 *                                  | iova/size (Mapped to domain)

 *

 * Imported       | DMA API         | dma_buf (Imported dma_buf)

 *

 * Imported       | IOMMU API       | dma_buf (Imported dma_buf),

 *                                  | gem->import_attach (Attachment on drm->dev),

 *                                  | sgt (Mapped to drm->dev)

 *                                  | iova/size (Mapped to domain)

 *

 * (*) If tegra->domain is set, i.e. TegraDRM IOMMU domain is directly managed through IOMMU API,

 *     this is IOMMU API. Otherwise DMA API.

 */

struct tegra_bo {

	struct drm_gem_object gem;

	struct host1x_bo base;
@@ -39,6 +59,7 @@ struct tegra_bo { 
	struct sg_table *sgt;

	dma_addr_t iova;

	void *vaddr;

	struct dma_buf *dma_buf;



	struct drm_mm_node *mm;

	unsigned long num_pages;