[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.koenig at 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