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| author | Marek Szyprowski <m.szyprowski@samsung.com> | 2014-04-22 13:14:08 +0200 |
|---|---|---|
| committer | Marek Szyprowski <m.szyprowski@samsung.com> | 2014-04-23 00:13:31 -0700 |
| commit | bba75455d47e71e0662c06508035333445481375 (patch) | |
| tree | a5ba3a04ae1b26ff6ef5d11400b79d66b288ae38 | |
| parent | 079dad139665e7d9331fcb9dc0f0bb3a2a4f4244 (diff) | |
| download | linux-3.10-bba75455d47e71e0662c06508035333445481375.tar.gz linux-3.10-bba75455d47e71e0662c06508035333445481375.tar.bz2 linux-3.10-bba75455d47e71e0662c06508035333445481375.zip | |
media: vb2-dma-contig: add a hack to speed up cache management
In most cases video processing is done with coherent (non-cachable) userspace mappings. In such case for USERPTR mode cache management can
be skipped. This patch introduces code for such optimisation. It is called
a hack, because it is not possible in generic way to detect if the
given userspace mapping is coherent on not.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Change-id: I86aa292455371f1b18eb3f6b765234dc04ff937b
| -rw-r--r-- | drivers/media/v4l2-core/videobuf2-dma-contig.c | 29 |
1 files changed, 27 insertions, 2 deletions
diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c index efdaca48d06..4e4d1753fb7 100644 --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c @@ -40,6 +40,7 @@ struct vb2_dc_buf { /* USERPTR related */ struct vm_area_struct *vma; + bool coherent; /* DMABUF related */ struct dma_buf_attachment *db_attach; @@ -114,7 +115,7 @@ static void vb2_dc_prepare(void *buf_priv) struct sg_table *sgt = buf->dma_sgt; /* DMABUF exporter will flush the cache for us */ - if (!sgt || buf->db_attach) + if (!sgt || buf->db_attach || buf->coherent) return; dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir); @@ -126,7 +127,7 @@ static void vb2_dc_finish(void *buf_priv) struct sg_table *sgt = buf->dma_sgt; /* DMABUF exporter will flush the cache for us */ - if (!sgt || buf->db_attach) + if (!sgt || buf->db_attach || buf->coherent) return; dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir); @@ -423,6 +424,28 @@ static inline int vma_is_io(struct vm_area_struct *vma) return !!(vma->vm_flags & (VM_IO | VM_PFNMAP)); } +#ifdef __arm__ +static inline int vma_is_coherent(struct vm_area_struct *vma) +{ + pgprot_t prot = vma->vm_page_prot; + /* + * this is a hack to speed up cache management on coherent arm mappings, + * other architectures rely on dma-mapping internal optimisations. + */ + if (vma_is_io(vma) || prot == pgprot_noncached(prot) || + prot == pgprot_writecombine(prot) || + prot == pgprot_dmacoherent(prot)) + return true; + + return false; +} +#else +static inline int vma_is_coherent(struct vm_area_struct *vma) +{ + return false; +} +#endif + static int vb2_dc_get_user_pfn(unsigned long start, int n_pages, struct vm_area_struct *vma, unsigned long *res) { @@ -614,6 +637,8 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr, goto fail_pages; } + buf->coherent = vma_is_coherent(vma); + /* extract page list from userspace mapping */ ret = vb2_dc_get_user_pages(start, pages, n_pages, vma, write); if (ret) { |