[PATCH 03/12] dma-buf: start caching of sg_table objects

[Christian König]

To allow a smooth transition from pinning buffer objects to dynamic
invalidation we first start to cache the sg_table for an attachment
unless the driver has implemented the explicite pin/unpin callbacks.

Signed-off-by: Christian König <christian.koe...@amd.com>
---
 drivers/dma-buf/dma-buf.c | 24 ++++++++++++++++++++++++
 include/linux/dma-buf.h   |  1 +
 2 files changed, 25 insertions(+)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 0656dcf289be..a18d10c4425a 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -610,6 +610,20 @@ dma_buf_attach(const struct dma_buf_attach_info *info)
        list_add(&attach->node, &dmabuf->attachments);
 
        mutex_unlock(&dmabuf->lock);
+
+       if (!dmabuf->ops->pin) {
+               struct sg_table *sgt;
+
+               sgt = dmabuf->ops->map_dma_buf(attach, DMA_BIDIRECTIONAL);
+               if (!sgt)
+                       sgt = ERR_PTR(-ENOMEM);
+               if (IS_ERR(sgt)) {
+                       dma_buf_detach(dmabuf, attach);
+                       return ERR_CAST(sgt);
+               }
+               attach->sgt = sgt;
+       }
+
        return attach;
 
 err_attach:
@@ -632,6 +646,10 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct 
dma_buf_attachment *attach)
        if (WARN_ON(!dmabuf || !attach))
                return;
 
+       if (attach->sgt)
+               dmabuf->ops->unmap_dma_buf(attach, attach->sgt,
+                                          DMA_BIDIRECTIONAL);
+
        mutex_lock(&dmabuf->lock);
        list_del(&attach->node);
        if (dmabuf->ops->detach)
@@ -668,6 +686,9 @@ struct sg_table *dma_buf_map_attachment(struct 
dma_buf_attachment *attach,
        if (WARN_ON(!attach || !attach->dmabuf))
                return ERR_PTR(-EINVAL);
 
+       if (attach->sgt)
+               return attach->sgt;
+
        reservation_object_lock(attach->dmabuf->resv, NULL);
        r = dma_buf_pin(attach->dmabuf);
        reservation_object_unlock(attach->dmabuf->resv);
@@ -701,6 +722,9 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment 
*attach,
        if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
                return;
 
+       if (attach->sgt == sg_table)
+               return;
+
        attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
                                                direction);
 
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 0321939b1c3d..b9d0719581cd 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -345,6 +345,7 @@ struct dma_buf_attachment {
        struct dma_buf *dmabuf;
        struct device *dev;
        struct list_head node;
+       struct sg_table *sgt;
        void *priv;
 };
 
-- 
2.17.1

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