From 660cd44659a05c5fbfce6d2bb1ce448aa0f35594 Mon Sep 17 00:00:00 2001 From: Shixiong Ou Date: Thu, 22 May 2025 15:07:12 +0800 Subject: [PATCH 3865/5403] drm/shmem-helper: Import dmabuf without mapping its sg_table [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 Acked-by: Thomas Zimmermann Signed-off-by: Thomas Zimmermann Link: https://lore.kernel.org/r/20250522070714.439824-1-oushixiong1025@163.com --- drivers/gpu/drm/drm_prime.c | 36 +++++++++++++++++++++++++++--------- include/drm/drm_prime.h | 3 +++ 2 files changed, 30 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index a1852c02f512..b703f83874e1 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -928,6 +928,26 @@ struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj, } EXPORT_SYMBOL(drm_gem_prime_export); + +/** + * drm_gem_is_prime_exported_dma_buf - + * checks if the DMA-BUF was exported from a GEM object belonging to @dev. + * @dev: drm_device to check against + * @dma_buf: dma-buf object to import + * + * Return: true if the DMA-BUF was exported from a GEM object belonging + * to @dev, false otherwise. + */ + +bool drm_gem_is_prime_exported_dma_buf(struct drm_device *dev, + struct dma_buf *dma_buf) +{ + struct drm_gem_object *obj = dma_buf->priv; + + return (dma_buf->ops == &drm_gem_prime_dmabuf_ops) && (obj->dev == dev); +} +EXPORT_SYMBOL(drm_gem_is_prime_exported_dma_buf); + /** * drm_gem_prime_import_dev - core implementation of the import callback * @dev: drm_device to import into @@ -951,16 +971,14 @@ struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev, struct drm_gem_object *obj; int ret; - if (dma_buf->ops == &drm_gem_prime_dmabuf_ops) { + if (drm_gem_is_prime_exported_dma_buf(dev, dma_buf)) { + /* + * Importing dmabuf exported from our own gem increases + * refcount on gem itself instead of f_count of dmabuf. + */ obj = dma_buf->priv; - if (obj->dev == dev) { - /* - * Importing dmabuf exported from our own gem increases - * refcount on gem itself instead of f_count of dmabuf. - */ - drm_gem_object_get(obj); - return obj; - } + drm_gem_object_get(obj); + return obj; } if (!dev->driver->gem_prime_import_sg_table) diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h index fa085c44d4ca..f50f862f0d8b 100644 --- a/include/drm/drm_prime.h +++ b/include/drm/drm_prime.h @@ -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); -- 2.54.0