This patch introduces usage of dma_map_sg to map memory behind a userspace pointer to a device as dma-contiguous mapping.
This patch contains some of the code kindly provided by Marek Szyprowski m.szyprowski@samsung.com and Kamil Debski k.debski@samsung.com and Andrzej Pietrasiewicz andrzej.p@samsung.com. Kind thanks for bug reports from Laurent Pinchart laurent.pinchart@ideasonboard.com and Seung-Woo Kim sw0312.kim@samsung.com.
Signed-off-by: Tomasz Stanislawski t.stanislaws@samsung.com Signed-off-by: Kyungmin Park kyungmin.park@samsung.com Acked-by: Laurent Pinchart laurent.pinchart@ideasonboard.com --- drivers/media/video/videobuf2-dma-contig.c | 226 ++++++++++++++++++++++++++-- 1 file changed, 210 insertions(+), 16 deletions(-)
diff --git a/drivers/media/video/videobuf2-dma-contig.c b/drivers/media/video/videobuf2-dma-contig.c index daac2b2..8486e06 100644 --- a/drivers/media/video/videobuf2-dma-contig.c +++ b/drivers/media/video/videobuf2-dma-contig.c @@ -11,6 +11,8 @@ */
#include <linux/module.h> +#include <linux/scatterlist.h> +#include <linux/sched.h> #include <linux/slab.h> #include <linux/dma-mapping.h>
@@ -27,6 +29,8 @@ struct vb2_dc_buf { void *vaddr; unsigned long size; dma_addr_t dma_addr; + enum dma_data_direction dma_dir; + struct sg_table *dma_sgt;
/* MMAP related */ struct vb2_vmarea_handler handler; @@ -37,6 +41,44 @@ struct vb2_dc_buf { };
/*********************************************/ +/* scatterlist table functions */ +/*********************************************/ + + +static void vb2_dc_sgt_foreach_page(struct sg_table *sgt, + void (*cb)(struct page *pg)) +{ + struct scatterlist *s; + unsigned int i; + + for_each_sg(sgt->sgl, s, sgt->orig_nents, i) { + struct page *page = sg_page(s); + unsigned int n_pages = PAGE_ALIGN(s->offset + s->length) + >> PAGE_SHIFT; + unsigned int j; + + for (j = 0; j < n_pages; ++j, ++page) + cb(page); + } +} + +static unsigned long vb2_dc_get_contiguous_size(struct sg_table *sgt) +{ + struct scatterlist *s; + dma_addr_t expected = sg_dma_address(sgt->sgl); + unsigned int i; + unsigned long size = 0; + + for_each_sg(sgt->sgl, s, sgt->nents, i) { + if (sg_dma_address(s) != expected) + break; + expected = sg_dma_address(s) + sg_dma_len(s); + size += sg_dma_len(s); + } + return size; +} + +/*********************************************/ /* callbacks for all buffers */ /*********************************************/
@@ -122,42 +164,194 @@ static int vb2_dc_mmap(void *buf_priv, struct vm_area_struct *vma) /* callbacks for USERPTR buffers */ /*********************************************/
+static inline int vma_is_io(struct vm_area_struct *vma) +{ + return !!(vma->vm_flags & (VM_IO | VM_PFNMAP)); +} + +static int vb2_dc_get_user_pages(unsigned long start, struct page **pages, + int n_pages, struct vm_area_struct *vma, int write) +{ + if (vma_is_io(vma)) { + unsigned int i; + + for (i = 0; i < n_pages; ++i, start += PAGE_SIZE) { + unsigned long pfn; + int ret = follow_pfn(vma, start, &pfn); + + if (ret) { + pr_err("no page for address %lu\n", start); + return ret; + } + pages[i] = pfn_to_page(pfn); + } + } else { + int n; + + n = get_user_pages(current, current->mm, start & PAGE_MASK, + n_pages, write, 1, pages, NULL); + /* negative error means that no page was pinned */ + n = max(n, 0); + if (n != n_pages) { + pr_err("got only %d of %d user pages\n", n, n_pages); + while (n) + put_page(pages[--n]); + return -EFAULT; + } + } + + return 0; +} + +static void vb2_dc_put_dirty_page(struct page *page) +{ + set_page_dirty_lock(page); + put_page(page); +} + +static void vb2_dc_put_userptr(void *buf_priv) +{ + struct vb2_dc_buf *buf = buf_priv; + struct sg_table *sgt = buf->dma_sgt; + + dma_unmap_sg(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir); + if (!vma_is_io(buf->vma)) + vb2_dc_sgt_foreach_page(sgt, vb2_dc_put_dirty_page); + + sg_free_table(sgt); + kfree(sgt); + vb2_put_vma(buf->vma); + kfree(buf); +} + static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr, - unsigned long size, int write) + unsigned long size, int write) { + struct vb2_dc_conf *conf = alloc_ctx; struct vb2_dc_buf *buf; + unsigned long start; + unsigned long end; + unsigned long offset; + struct page **pages; + int n_pages; + int ret = 0; struct vm_area_struct *vma; - dma_addr_t dma_addr = 0; - int ret; + struct sg_table *sgt; + unsigned long contig_size;
buf = kzalloc(sizeof *buf, GFP_KERNEL); if (!buf) return ERR_PTR(-ENOMEM);
- ret = vb2_get_contig_userptr(vaddr, size, &vma, &dma_addr); + buf->dev = conf->dev; + buf->dma_dir = write ? DMA_FROM_DEVICE : DMA_TO_DEVICE; + + start = vaddr & PAGE_MASK; + offset = vaddr & ~PAGE_MASK; + end = PAGE_ALIGN(vaddr + size); + n_pages = (end - start) >> PAGE_SHIFT; + + pages = kmalloc(n_pages * sizeof(pages[0]), GFP_KERNEL); + if (!pages) { + ret = -ENOMEM; + pr_err("failed to allocate pages table\n"); + goto fail_buf; + } + + /* current->mm->mmap_sem is taken by videobuf2 core */ + vma = find_vma(current->mm, vaddr); + if (!vma) { + pr_err("no vma for address %lu\n", vaddr); + ret = -EFAULT; + goto fail_pages; + } + + if (vma->vm_end < vaddr + size) { + pr_err("vma at %lu is too small for %lu bytes\n", vaddr, size); + ret = -EFAULT; + goto fail_pages; + } + + buf->vma = vb2_get_vma(vma); + if (!buf->vma) { + pr_err("failed to copy vma\n"); + ret = -ENOMEM; + goto fail_pages; + } + + /* extract page list from userspace mapping */ + ret = vb2_dc_get_user_pages(start, pages, n_pages, vma, write); if (ret) { - printk(KERN_ERR "Failed acquiring VMA for vaddr 0x%08lx\n", - vaddr); - kfree(buf); - return ERR_PTR(ret); + pr_err("failed to get user pages\n"); + goto fail_vma; + } + + sgt = kzalloc(sizeof(*sgt), GFP_KERNEL); + if (!sgt) { + pr_err("failed to allocate sg table\n"); + ret = -ENOMEM; + goto fail_get_user_pages; + } + + ret = sg_alloc_table_from_pages(sgt, pages, n_pages, + offset, size, GFP_KERNEL); + if (ret) { + pr_err("failed to initialize sg table\n"); + goto fail_sgt; + } + + /* pages are no longer needed */ + kfree(pages); + pages = NULL; + + sgt->nents = dma_map_sg(buf->dev, sgt->sgl, sgt->orig_nents, + buf->dma_dir); + if (sgt->nents <= 0) { + pr_err("failed to map scatterlist\n"); + ret = -EIO; + goto fail_sgt_init; + } + + contig_size = vb2_dc_get_contiguous_size(sgt); + if (contig_size < size) { + pr_err("contiguous mapping is too small %lu/%lu\n", + contig_size, size); + ret = -EFAULT; + goto fail_map_sg; }
+ buf->dma_addr = sg_dma_address(sgt->sgl); buf->size = size; - buf->dma_addr = dma_addr; - buf->vma = vma; + buf->dma_sgt = sgt;
return buf; -}
-static void vb2_dc_put_userptr(void *mem_priv) -{ - struct vb2_dc_buf *buf = mem_priv; +fail_map_sg: + dma_unmap_sg(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
- if (!buf) - return; +fail_sgt_init: + if (!vma_is_io(buf->vma)) + vb2_dc_sgt_foreach_page(sgt, put_page); + sg_free_table(sgt); + +fail_sgt: + kfree(sgt);
+fail_get_user_pages: + if (pages && !vma_is_io(buf->vma)) + while (n_pages) + put_page(pages[--n_pages]); + +fail_vma: vb2_put_vma(buf->vma); + +fail_pages: + kfree(pages); /* kfree is NULL-proof */ + +fail_buf: kfree(buf); + + return ERR_PTR(ret); }
/*********************************************/