Am 25.03.25 um 14:37 schrieb Jacek Lawrynowicz:
> Use DMA_ATTR_SKIP_CPU_SYNC flag for exported buffers during DMA mapping.
> The same flag is already used by drm_gem_map_dma_buf() for imported
> buffers.
>
> Signed-off-by: Jacek Lawrynowicz <jacek.lawrynow...@linux.intel.com>
> ---
> drivers/gpu/drm/drm_gem_shmem_helper.c | 8 ++++++--
> include/drm/drm_gem.h | 12 ++++++++++++
> 2 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
> b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index d99dee67353a1..8938d8e3de52f 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -699,7 +699,7 @@ EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);
> static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct
> drm_gem_shmem_object *shmem)
> {
> struct drm_gem_object *obj = &shmem->base;
> - int ret;
> + int ret, flags = 0;
> struct sg_table *sgt;
>
> if (shmem->sgt)
> @@ -716,8 +716,12 @@ static struct sg_table
> *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
> ret = PTR_ERR(sgt);
> goto err_put_pages;
> }
> +
> + if (drm_gem_is_exported())
> + flags |= DMA_ATTR_SKIP_CPU_SYNC;
We should probably just unconditionally set this flag or not at all.
Otherwise we could run into quite some surprises.
Regards,
Christian.
> +
> /* Map the pages for use by the h/w. */
> - ret = dma_map_sgtable(obj->dev->dev, sgt, DMA_BIDIRECTIONAL, 0);
> + ret = dma_map_sgtable(obj->dev->dev, sgt, DMA_BIDIRECTIONAL, flags);
> if (ret)
> goto err_free_sgt;
>
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index 2bf893eabb4b2..7c355a44d0a49 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -589,6 +589,18 @@ static inline bool drm_gem_is_imported(const struct
> drm_gem_object *obj)
> return obj->dma_buf && (obj->dma_buf->priv != obj);
> }
>
> +/**
> + * drm_gem_is_exported() - Tests if GEM object's buffer has been exported
> + * @obj: the GEM object
> + *
> + * Returns:
> + * True if the GEM object's buffer has been exported, false otherwise
> + */
> +static inline bool drm_gem_is_exported(const struct drm_gem_object *obj)
> +{
> + return obj->dma_buf && (obj->dma_buf->priv == obj);
> +}
> +
> #ifdef CONFIG_LOCKDEP
> /**
> * drm_gem_gpuva_set_lock() - Set the lock protecting accesses to the gpuva
> list.
