drm/exynos: add dmabuf attach/detach callbacks.

With this patch, When dma_buf_unmap_attachment is called,
the pages of sgt aren't unmapped from iommu table.
Instead, when dma_buf_detach is called, that would be done.

And also removes exynos_get_sgt function used to get clone sgt
and uses attachment's sgt instead. This patch would resolve
performance deterioration issue when v4l2-based driver is using
the buffer imported from gem.

This change is derived from videobuf2-dma-contig.c

Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

1 files changed, 73 insertions, 31 deletions

diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
index 539da9f4eb97..61d5a8402eb8 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
@@ -30,63 +30,107 @@
 
 #include <linux/dma-buf.h>
 
-static struct sg_table *exynos_get_sgt(struct drm_device *drm_dev,
-                                        struct exynos_drm_gem_buf *buf)
+struct exynos_drm_dmabuf_attachment {
+        struct sg_table sgt;
+        enum dma_data_direction dir;
+};
+
+static int exynos_gem_attach_dma_buf(struct dma_buf *dmabuf,
+                                        struct device *dev,
+                                        struct dma_buf_attachment *attach)
 {
-        struct sg_table *sgt = NULL;
-        int ret;
+        struct exynos_drm_dmabuf_attachment *exynos_attach;
 
-        sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
-        if (!sgt)
-                goto out;
+        exynos_attach = kzalloc(sizeof(*exynos_attach), GFP_KERNEL);
+        if (!exynos_attach)
+                return -ENOMEM;
 
-        ret = dma_get_sgtable(drm_dev->dev, sgt, buf->kvaddr,
-                                buf->dma_addr, buf->size);
-        if (ret < 0) {
-                DRM_ERROR("failed to get sgtable.\n");
-                goto err_free_sgt;
-        }
+        exynos_attach->dir = DMA_NONE;
+        attach->priv = exynos_attach;
 
-        return sgt;
+        return 0;
+}
 
-err_free_sgt:
-        kfree(sgt);
-        sgt = NULL;
-out:
-        return NULL;
+static void exynos_gem_detach_dma_buf(struct dma_buf *dmabuf,
+                                        struct dma_buf_attachment *attach)
+{
+        struct exynos_drm_dmabuf_attachment *exynos_attach = attach->priv;
+        struct sg_table *sgt;
+
+        if (!exynos_attach)
+                return;
+
+        sgt = &exynos_attach->sgt;
+
+        if (exynos_attach->dir != DMA_NONE)
+                dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents,
+                                exynos_attach->dir);
+
+        sg_free_table(sgt);
+        kfree(exynos_attach);
+        attach->priv = NULL;
 }
 
 static struct sg_table *
                 exynos_gem_map_dma_buf(struct dma_buf_attachment *attach,
                                         enum dma_data_direction dir)
 {
+        struct exynos_drm_dmabuf_attachment *exynos_attach = attach->priv;
         struct exynos_drm_gem_obj *gem_obj = attach->dmabuf->priv;
         struct drm_device *dev = gem_obj->base.dev;
         struct exynos_drm_gem_buf *buf;
+        struct scatterlist *rd, *wr;
         struct sg_table *sgt = NULL;
-        int nents;
+        unsigned int i;
+        int nents, ret;
 
         DRM_DEBUG_PRIME("%s\n", __FILE__);
 
+        if (WARN_ON(dir == DMA_NONE))
+                return ERR_PTR(-EINVAL);
+
+        /* just return current sgt if already requested. */
+        if (exynos_attach->dir == dir)
+                return &exynos_attach->sgt;
+
+        /* reattaching is not allowed. */
+        if (WARN_ON(exynos_attach->dir != DMA_NONE))
+                return ERR_PTR(-EBUSY);
+
         buf = gem_obj->buffer;
         if (!buf) {
                 DRM_ERROR("buffer is null.\n");
-                return sgt;
+                return ERR_PTR(-ENOMEM);
+        }
+
+        sgt = &exynos_attach->sgt;
+
+        ret = sg_alloc_table(sgt, buf->sgt->orig_nents, GFP_KERNEL);
+        if (ret) {
+                DRM_ERROR("failed to alloc sgt.\n");
+                return ERR_PTR(-ENOMEM);
         }
 
         mutex_lock(&dev->struct_mutex);
 
-        sgt = exynos_get_sgt(dev, buf);
-        if (!sgt)
-                goto err_unlock;
+        rd = buf->sgt->sgl;
+        wr = sgt->sgl;
+        for (i = 0; i < sgt->orig_nents; ++i) {
+                sg_set_page(wr, sg_page(rd), rd->length, rd->offset);
+                rd = sg_next(rd);
+                wr = sg_next(wr);
+        }
 
-        nents = dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir);
+        nents = dma_map_sg(attach->dev, sgt->sgl, sgt->orig_nents, dir);
         if (!nents) {
                 DRM_ERROR("failed to map sgl with iommu.\n");
-                sgt = NULL;
+                sgt = ERR_PTR(-EIO);
                 goto err_unlock;
         }
 
+        exynos_attach->dir = dir;
+        attach->priv = exynos_attach;
+
         DRM_DEBUG_PRIME("buffer size = 0x%lx\n", buf->size);
 
 err_unlock:
@@ -98,11 +142,7 @@ static void exynos_gem_unmap_dma_buf(struct dma_buf_attachment *attach,
                                                 struct sg_table *sgt,
                                                 enum dma_data_direction dir)
 {
-        dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, dir);
-
-        sg_free_table(sgt);
-        kfree(sgt);
-        sgt = NULL;
+        /* Nothing to do. */
 }
 
 static void exynos_dmabuf_release(struct dma_buf *dmabuf)
@@ -164,6 +204,8 @@ static int exynos_gem_dmabuf_mmap(struct dma_buf *dma_buf,
 }
 
 static struct dma_buf_ops exynos_dmabuf_ops = {
+        .attach                 = exynos_gem_attach_dma_buf,
+        .detach                 = exynos_gem_detach_dma_buf,
         .map_dma_buf            = exynos_gem_map_dma_buf,
         .unmap_dma_buf          = exynos_gem_unmap_dma_buf,
         .kmap                   = exynos_gem_dmabuf_kmap,