iommu sg merging: add device_dma_parameters structure
IOMMUs merges scatter/gather segments without considering a low level
driver's restrictions. The problem is that IOMMUs can't access to the
limitations because they are in request_queue.
This patchset introduces a new structure, device_dma_parameters,
including dma information. A pointer to device_dma_parameters is added
to struct device. The bus specific structures (like pci_dev) includes
device_dma_parameters. Low level drivers can use dma_set_max_seg_size
to tell IOMMUs about the restrictions.
We can move more dma stuff in struct device (like dma_mask) to struct
device_dma_parameters later (needs some cleanups before that).
This includes patches for all the IOMMUs that could merge sg (x86_64,
ppc, IA64, alpha, sparc64, and parisc) though only the ppc patch was
tested. The patches for other IOMMUs are only compile tested.
This patch:
Add a new structure, device_dma_parameters, including dma information. A
pointer to device_dma_parameters is added to struct device.
- there are only max_segment_size and segment_boundary_mask there but we'll
move more dma stuff in struct device (like dma_mask) to struct
device_dma_parameters later. segment_boundary_mask is not supported yet.
- new accessors for the dma parameters are added. So we can easily change
where to place struct device_dma_parameters in the future.
- dma_get_max_seg_size returns 64K if dma_parms in struct device isn't set
up properly. 64K is the default max_segment_size in the block layer.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Jeff Garzik <jeff@garzik.org>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 4470950..df3a361 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -60,6 +60,21 @@
extern u64 dma_get_required_mask(struct device *dev);
+static inline unsigned int dma_get_max_seg_size(struct device *dev)
+{
+ return dev->dma_parms ? dev->dma_parms->max_segment_size : 65536;
+}
+
+static inline unsigned int dma_set_max_seg_size(struct device *dev,
+ unsigned int size)
+{
+ if (dev->dma_parms) {
+ dev->dma_parms->max_segment_size = size;
+ return 0;
+ } else
+ return -EIO;
+}
+
/* flags for the coherent memory api */
#define DMA_MEMORY_MAP 0x01
#define DMA_MEMORY_IO 0x02