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drm/shmem-helper: Import dmabuf without mapping its sg_table

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[WHY]
1. Drivers using DRM_GEM_SHADOW_PLANE_HELPER_FUNCS and
   DRM_GEM_SHMEM_DRIVER_OPS (e.g., udl, ast) do not require
   sg_table import.
   They only need dma_buf_vmap() to access the shared buffer's
   kernel virtual address.

2. On certain Aspeed-based boards, a dma_mask of 0xffff_ffff may
   trigger SWIOTLB during dmabuf import. However, IO_TLB_SEGSIZE
   restricts the maximum DMA streaming mapping memory, resulting in
   errors like:

   ast 0000:07:00.0: swiotlb buffer is full (sz: 3145728 bytes), total 32768 (slots), used 0 (slots)

[HOW]
Provide a gem_prime_import implementation without sg_table mapping
to avoid issues (e.g., "swiotlb buffer is full"). Drivers that do not
require sg_table can adopt this.

Signed-off-by: Shixiong Ou <oushixiong@kylinos.cn>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20250522070714.439824-1-oushixiong1025@163.com
This commit is contained in:
Shixiong Ou
2025-05-22 15:07:12 +08:00
committed by Thomas Zimmermann
parent 6048f55876
commit 660cd44659
4 changed files with 102 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
include/drm/drm_gem_shmem_helper.h
View File

@@ -287,6 +287,8 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
struct sg_table *sgt);
int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
struct drm_mode_create_dumb *args);
struct drm_gem_object *drm_gem_shmem_prime_import_no_map(struct drm_device *dev,
struct dma_buf *buf);
/**
* DRM_GEM_SHMEM_DRIVER_OPS - Default shmem GEM operations
@@ -298,4 +300,17 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
.gem_prime_import_sg_table = drm_gem_shmem_prime_import_sg_table, \
.dumb_create = drm_gem_shmem_dumb_create
/**
* DRM_GEM_SHMEM_DRIVER_OPS_NO_MAP_SGT - shmem GEM operations
* without mapping sg_table on
* imported buffer.
*
* This macro provides a shortcut for setting the shmem GEM operations in
* the &drm_driver structure for drivers that do not require a sg_table on
* imported buffers.
*/
#define DRM_GEM_SHMEM_DRIVER_OPS_NO_MAP_SGT \
.gem_prime_import = drm_gem_shmem_prime_import_no_map, \
.dumb_create = drm_gem_shmem_dumb_create
#endif /* __DRM_GEM_SHMEM_HELPER_H__ */

3
include/drm/drm_prime.h
View File

@@ -100,6 +100,9 @@ struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj,
unsigned long drm_prime_get_contiguous_size(struct sg_table *sgt);
/* helper functions for importing */
bool drm_gem_is_prime_exported_dma_buf(struct drm_device *dev,
struct dma_buf *dma_buf);
struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev,
struct dma_buf *dma_buf,
struct device *attach_dev);