From 6b7b651055221127304a4e373ee9b762398d54d7 Mon Sep 17 00:00:00 2001 From: FUJITA Tomonori Date: Mon, 4 Feb 2008 22:27:55 -0800 Subject: [PATCH] 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 Acked-by: Jeff Garzik Cc: James Bottomley Acked-by: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/device.h | 11 +++++++++++ include/linux/dma-mapping.h | 15 +++++++++++++++ 2 files changed, 26 insertions(+) diff --git a/include/linux/device.h b/include/linux/device.h index 479c0b31593..2258d89bf52 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -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 diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 4470950892b..df3a3610caf 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -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 -- 2.41.1