[media] v4l: vb2-dma-contig: add support for scatterlist in userptr mode
authorTomasz Stanislawski <t.stanislaws@samsung.com>
Thu, 14 Jun 2012 13:37:42 +0000 (10:37 -0300)
committerMauro Carvalho Chehab <mchehab@redhat.com>
Sun, 25 Nov 2012 19:12:03 +0000 (17:12 -0200)
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>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
drivers/media/v4l2-core/videobuf2-dma-contig.c

index daac2b2de35779a4ad66f48be21074bb5bb2d334..8486e06cb618bcb46c6d276f7f2c46a0402d2527 100644 (file)
@@ -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;
@@ -36,6 +40,44 @@ struct vb2_dc_buf {
        struct vm_area_struct           *vma;
 };
 
+/*********************************************/
+/*        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);
 }
 
 /*********************************************/