[PATCH 5/5] udmabuf: implement begin_cpu_access/end_cpu_access hooks

[Gurchetan Singh]

With the misc device, we should end up using the result of
get_arch_dma_ops(..) or dma-direct ops.

This can allow us to have WC mappings in the guest after
synchronization.

Signed-off-by: Gurchetan Singh <gurchetansingh at chromium.org>
---
 drivers/dma-buf/udmabuf.c | 40 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 67e89bb034c5..142444922acd 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -19,6 +19,7 @@ struct udmabuf {
 	u32 flags;
 	pgoff_t pagecount;
 	struct page **pages;
+	struct sg_table *sg;
 	struct miscdevice *device;
 };
 
@@ -105,8 +106,12 @@ static void unmap_udmabuf(struct dma_buf_attachment *at,
 static void release_udmabuf(struct dma_buf *buf)
 {
 	struct udmabuf *ubuf = buf->priv;
+	struct device *dev = ubuf->device->this_device;
 	pgoff_t pg;
 
+	if (ubuf->sg)
+		put_sg_table(dev, ubuf->sg, DMA_BIDIRECTIONAL);
+
 	for (pg = 0; pg < ubuf->pagecount; pg++)
 		put_page(ubuf->pages[pg]);
 	kfree(ubuf->pages);
@@ -127,6 +132,39 @@ static void kunmap_udmabuf(struct dma_buf *buf, unsigned long page_num,
 	kunmap(vaddr);
 }
 
+static int begin_cpu_udmabuf(struct dma_buf *buf,
+			     enum dma_data_direction direction)
+{
+	struct udmabuf *ubuf = buf->priv;
+	struct device *dev = ubuf->device->this_device;
+
+	if (!ubuf->sg) {
+		ubuf->sg = get_sg_table(dev, buf, direction);
+		if (IS_ERR(ubuf->sg))
+			return PTR_ERR(ubuf->sg);
+	} else {
+		dma_sync_sg_for_device(dev, ubuf->sg->sgl,
+				       ubuf->sg->nents,
+				       direction);
+	}
+
+	return 0;
+}
+
+static int end_cpu_udmabuf(struct dma_buf *buf,
+			   enum dma_data_direction direction)
+{
+	struct udmabuf *ubuf = buf->priv;
+	struct device *dev = ubuf->device->this_device;
+
+	if (!ubuf->sg)
+		return -EINVAL;
+
+	dma_sync_sg_for_cpu(dev, ubuf->sg->sgl, ubuf->sg->nents, direction);
+	return 0;
+}
+
+
 static const struct dma_buf_ops udmabuf_ops = {
 	.cache_sgt_mapping = true,
 	.map_dma_buf	   = map_udmabuf,
@@ -135,6 +173,8 @@ static const struct dma_buf_ops udmabuf_ops = {
 	.map		   = kmap_udmabuf,
 	.unmap		   = kunmap_udmabuf,
 	.mmap		   = mmap_udmabuf,
+	.begin_cpu_access  = begin_cpu_udmabuf,
+	.end_cpu_access    = end_cpu_udmabuf,
 };
 
 #define SEALS_WANTED (F_SEAL_SHRINK)
-- 
2.24.0.432.g9d3f5f5b63-goog