Start to fix the coherency issues for non PCI devices by adding a dma_coherent
flag to the DMA-buf.
The flag should be set by the exporter if only devices which can do coherent
DMA-access with respect to the CPU cache are allowed to access the buffer.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
drivers/dma-buf/dma-buf.c | 5 +++++
include/linux/dma-buf.h | 16 ++++++++++++++++
2 files changed, 21 insertions(+)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index c40d72d318fd..7509807bf485 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -15,6 +15,7 @@
#include <linux/slab.h>
#include <linux/dma-buf.h>
#include <linux/dma-fence.h>
+#include <linux/dma-map-ops.h>
#include <linux/anon_inodes.h>
#include <linux/export.h>
#include <linux/debugfs.h>
@@ -635,6 +636,7 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
dmabuf->priv = exp_info->priv;
dmabuf->ops = exp_info->ops;
+ dmabuf->dma_coherent = exp_info->coherent;
dmabuf->size = exp_info->size;
dmabuf->exp_name = exp_info->exp_name;
dmabuf->owner = exp_info->owner;
@@ -894,6 +896,9 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
if (WARN_ON(importer_ops && !importer_ops->move_notify))
return ERR_PTR(-EINVAL);
+ if (dmabuf->dma_coherent && !dev_is_dma_coherent(dev))
+ return ERR_PTR(-EINVAL);
+
attach = kzalloc(sizeof(*attach), GFP_KERNEL);
if (!attach)
return ERR_PTR(-ENOMEM);
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 6fa8d4e29719..f2083b94b116 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -326,6 +326,20 @@ struct dma_buf {
/** @ops: dma_buf_ops associated with this buffer object. */
const struct dma_buf_ops *ops;
+ /**
+ * @dma_coherent:
+ *
+ * True if the buffer is backed by DMA coherent memory with respect to
+ * the CPU cache even if the architecture can support incoherent
+ * devices.
+ *
+ * Usually mirrors the result of dev_is_dma_coherent() of the exporter,
+ * but can be cleared by the exporter to allow incoherent devices
+ * access to the buffer if the exporter takes care of coherency for CPU
+ * accesses.
+ */
+ bool dma_coherent;
+
/**
* @vmapping_counter:
*
@@ -524,6 +538,7 @@ struct dma_buf_attachment {
* @ops: Attach allocator-defined dma buf ops to the new buffer
* @size: Size of the buffer - invariant over the lifetime of the buffer
* @flags: mode flags for the file
+ * @coherent: If DMA accesses must be coherent to the CPU cache.
* @resv: reservation-object, NULL to allocate default one
* @priv: Attach private data of allocator to this buffer
*
@@ -536,6 +551,7 @@ struct dma_buf_export_info {
const struct dma_buf_ops *ops;
size_t size;
int flags;
+ bool coherent;
struct dma_resv *resv;
void *priv;
};
--
2.25.1
