Commit 6b7b6510 authored Feb 04, 2008 by FUJITA Tomonori Committed by Linus Torvalds Feb 05, 2008

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>

parent 7bbdc3d5

include/linux/device.h

+11 −0

Original line number	Diff line number	Diff line
		@@ -410,6 +410,15 @@ extern int devres_release_group(struct device dev, void id);
		extern void devm_kzalloc(struct device dev, size_t size, gfp_t gfp);
		extern void devm_kfree(struct device dev, void p);

		struct device_dma_parameters {
		/*
		* a low level driver may set these to teach IOMMU code about
		* sg limitations.
		*/
		unsigned int max_segment_size;
		unsigned long segment_boundary_mask;
		};

		struct device {
		struct klist klist_children;
		struct klist_node knode_parent; /* node in sibling list */
		@@ -445,6 +454,8 @@ struct device {
		64 bit addresses for consistent
		allocations such descriptors. */

		struct device_dma_parameters *dma_parms;

		struct list_head dma_pools; /* dma pools (if dma'ble) */

		struct dma_coherent_mem dma_mem; / internal for coherent mem

include/linux/dma-mapping.h

+15 −0

Original line number	Diff line number	Diff line
		@@ -60,6 +60,21 @@ static inline int is_device_dma_capable(struct device *dev)

		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