Re: [PATCH 4/7] dma-mapping: add a dma_alloc_noncontiguous API
On Tue, Feb 16, 2021 at 06:55:39PM +, Robin Murphy wrote: > On 2021-02-02 09:51, Christoph Hellwig wrote: >> Add a new API that returns a potentiall virtually non-contigous sg_table >> and a DMA address. This API is only properly implemented for dma-iommu >> and will simply return a contigious chunk as a fallback. >> >> The intent is that media drivers can use this API if either: >> >> - no kernel mapping or only temporary kernel mappings are required. >> That is as a better replacement for DMA_ATTR_NO_KERNEL_MAPPING >> - a kernel mapping is required for cached and DMA mapped pages, but >> the driver also needs the pages to e.g. map them to userspace. >> In that sense it is a replacement for some aspects of the recently >> removed and never fully implemented DMA_ATTR_NON_CONSISTENT >> >> Signed-off-by: Christoph Hellwig >> --- >> Documentation/core-api/dma-api.rst | 74 + >> include/linux/dma-map-ops.h| 18 + >> include/linux/dma-mapping.h| 31 + >> kernel/dma/mapping.c | 103 + >> 4 files changed, 226 insertions(+) >> >> diff --git a/Documentation/core-api/dma-api.rst >> b/Documentation/core-api/dma-api.rst >> index 157a474ae54416..e24b2447f4bfe6 100644 >> --- a/Documentation/core-api/dma-api.rst >> +++ b/Documentation/core-api/dma-api.rst >> @@ -594,6 +594,80 @@ dev, size, dma_handle and dir must all be the same as >> those passed into >> dma_alloc_noncoherent(). cpu_addr must be the virtual address returned by >> dma_alloc_noncoherent(). >> +:: >> + >> +struct sg_table * >> +dma_alloc_noncontiguous(struct device *dev, size_t size, >> +enum dma_data_direction dir, gfp_t gfp) >> + >> +This routine allocates bytes of non-coherent and possibly >> non-contiguous >> +memory. It returns a pointer to struct sg_table that describes the >> allocated >> +and DMA mapped memory, or NULL if the allocation failed. The resulting >> memory >> +can be used for struct page mapped into a scatterlist are suitable for. >> + >> +The return sg_table is guaranteed to have 1 single DMA mapped segment as >> +indicated by sgt->nents, but it might have multiple CPU side segments as >> +indicated by sgt->orig_nents. >> + >> +The dir parameter specified if data is read and/or written by the device, >> +see dma_map_single() for details. >> + >> +The gfp parameter allows the caller to specify the ``GFP_`` flags (see >> +kmalloc()) for the allocation, but rejects flags used to specify a memory >> +zone such as GFP_DMA or GFP_HIGHMEM. >> + >> +Before giving the memory to the device, dma_sync_sgtable_for_device() needs >> +to be called, and before reading memory written by the device, >> +dma_sync_sgtable_for_cpu(), just like for streaming DMA mappings that are >> +reused. >> + >> +:: >> + >> +void >> +dma_free_noncontiguous(struct device *dev, size_t size, >> + struct sg_table *sgt, >> + enum dma_data_direction dir) >> + >> +Free memory previously allocated using dma_alloc_noncontiguous(). dev, >> size, >> +and dir must all be the same as those passed into dma_alloc_noncontiguous(). >> +sgt must be the pointer returned by dma_alloc_noncontiguous(). >> + >> +:: >> + >> +void * >> +dma_vmap_noncontiguous(struct device *dev, size_t size, >> +struct sg_table *sgt) >> + >> +Return a contiguous kernel mapping for an allocation returned from >> +dma_alloc_noncontiguous(). dev and size must be the same as those passed >> into >> +dma_alloc_noncontiguous(). sgt must be the pointer returned by >> +dma_alloc_noncontiguous(). >> + >> +Once a non-contiguous allocation is mapped using this function, the >> +flush_kernel_vmap_range() and invalidate_kernel_vmap_range() APIs must be >> used >> +to manage the coherency of the kernel mapping. > > Maybe say something like "coherency between the kernel mapping and any > userspace mappings"? Otherwise people like me may be easily confused and > think it's referring to coherency between the kernel mapping and the > device, where in most cases those APIs won't help at all :) Well, it is all of the above for a VIVT cache setup. I've ammended it to: Once a non-contiguous allocation is mapped using this function, the flush_kernel_vmap_range() and invalidate_kernel_vmap_range() APIs must be used to manage the coherency between the kernel mapping, the device and user space mappings (if any). ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH 4/7] dma-mapping: add a dma_alloc_noncontiguous API
On 2021-02-02 09:51, Christoph Hellwig wrote:
Add a new API that returns a potentiall virtually non-contigous sg_table
and a DMA address. This API is only properly implemented for dma-iommu
and will simply return a contigious chunk as a fallback.
The intent is that media drivers can use this API if either:
- no kernel mapping or only temporary kernel mappings are required.
That is as a better replacement for DMA_ATTR_NO_KERNEL_MAPPING
- a kernel mapping is required for cached and DMA mapped pages, but
the driver also needs the pages to e.g. map them to userspace.
In that sense it is a replacement for some aspects of the recently
removed and never fully implemented DMA_ATTR_NON_CONSISTENT
Signed-off-by: Christoph Hellwig
---
Documentation/core-api/dma-api.rst | 74 +
include/linux/dma-map-ops.h| 18 +
include/linux/dma-mapping.h| 31 +
kernel/dma/mapping.c | 103 +
4 files changed, 226 insertions(+)
diff --git a/Documentation/core-api/dma-api.rst
b/Documentation/core-api/dma-api.rst
index 157a474ae54416..e24b2447f4bfe6 100644
--- a/Documentation/core-api/dma-api.rst
+++ b/Documentation/core-api/dma-api.rst
@@ -594,6 +594,80 @@ dev, size, dma_handle and dir must all be the same as
those passed into
dma_alloc_noncoherent(). cpu_addr must be the virtual address returned by
dma_alloc_noncoherent().
+::
+
+ struct sg_table *
+ dma_alloc_noncontiguous(struct device *dev, size_t size,
+ enum dma_data_direction dir, gfp_t gfp)
+
+This routine allocates bytes of non-coherent and possibly
non-contiguous
+memory. It returns a pointer to struct sg_table that describes the allocated
+and DMA mapped memory, or NULL if the allocation failed. The resulting memory
+can be used for struct page mapped into a scatterlist are suitable for.
+
+The return sg_table is guaranteed to have 1 single DMA mapped segment as
+indicated by sgt->nents, but it might have multiple CPU side segments as
+indicated by sgt->orig_nents.
+
+The dir parameter specified if data is read and/or written by the device,
+see dma_map_single() for details.
+
+The gfp parameter allows the caller to specify the ``GFP_`` flags (see
+kmalloc()) for the allocation, but rejects flags used to specify a memory
+zone such as GFP_DMA or GFP_HIGHMEM.
+
+Before giving the memory to the device, dma_sync_sgtable_for_device() needs
+to be called, and before reading memory written by the device,
+dma_sync_sgtable_for_cpu(), just like for streaming DMA mappings that are
+reused.
+
+::
+
+ void
+ dma_free_noncontiguous(struct device *dev, size_t size,
+ struct sg_table *sgt,
+ enum dma_data_direction dir)
+
+Free memory previously allocated using dma_alloc_noncontiguous(). dev, size,
+and dir must all be the same as those passed into dma_alloc_noncontiguous().
+sgt must be the pointer returned by dma_alloc_noncontiguous().
+
+::
+
+ void *
+ dma_vmap_noncontiguous(struct device *dev, size_t size,
+ struct sg_table *sgt)
+
+Return a contiguous kernel mapping for an allocation returned from
+dma_alloc_noncontiguous(). dev and size must be the same as those passed into
+dma_alloc_noncontiguous(). sgt must be the pointer returned by
+dma_alloc_noncontiguous().
+
+Once a non-contiguous allocation is mapped using this function, the
+flush_kernel_vmap_range() and invalidate_kernel_vmap_range() APIs must be used
+to manage the coherency of the kernel mapping.
Maybe say something like "coherency between the kernel mapping and any
userspace mappings"? Otherwise people like me may be easily confused and
think it's referring to coherency between the kernel mapping and the
device, where in most cases those APIs won't help at all :)
+
+::
+
+ void
+ dma_vunmap_noncontiguous(struct device *dev, void *vaddr)
+
+Unmap a kernel mapping returned by dma_vmap_noncontiguous(). dev must be the
+same the one passed into dma_alloc_noncontiguous(). vaddr must be the pointer
+returned by dma_vmap_noncontiguous().
+
+
+::
+
+ int
+ dma_mmap_noncontiguous(struct device *dev, struct vm_area_struct *vma,
+ size_t size, struct sg_table *sgt)
+
+Map an allocation returned from dma_alloc_noncontiguous() into a user address
+space. dev and size must be the same as those passed into
+dma_alloc_noncontiguous(). sgt must be the pointer returned by
+dma_alloc_noncontiguous().
+
::
int
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 11e02537b9e01b..fe46a41130e662 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -22,6 +22,10 @@ struct dma_map_ops {
gfp_t gfp);
void (*free_pages)(struct device *dev, size_t size, struct page *vaddr,
dma_addr_t
[PATCH 4/7] dma-mapping: add a dma_alloc_noncontiguous API
Add a new API that returns a potentiall virtually non-contigous sg_table
and a DMA address. This API is only properly implemented for dma-iommu
and will simply return a contigious chunk as a fallback.
The intent is that media drivers can use this API if either:
- no kernel mapping or only temporary kernel mappings are required.
That is as a better replacement for DMA_ATTR_NO_KERNEL_MAPPING
- a kernel mapping is required for cached and DMA mapped pages, but
the driver also needs the pages to e.g. map them to userspace.
In that sense it is a replacement for some aspects of the recently
removed and never fully implemented DMA_ATTR_NON_CONSISTENT
Signed-off-by: Christoph Hellwig
---
Documentation/core-api/dma-api.rst | 74 +
include/linux/dma-map-ops.h| 18 +
include/linux/dma-mapping.h| 31 +
kernel/dma/mapping.c | 103 +
4 files changed, 226 insertions(+)
diff --git a/Documentation/core-api/dma-api.rst
b/Documentation/core-api/dma-api.rst
index 157a474ae54416..e24b2447f4bfe6 100644
--- a/Documentation/core-api/dma-api.rst
+++ b/Documentation/core-api/dma-api.rst
@@ -594,6 +594,80 @@ dev, size, dma_handle and dir must all be the same as
those passed into
dma_alloc_noncoherent(). cpu_addr must be the virtual address returned by
dma_alloc_noncoherent().
+::
+
+ struct sg_table *
+ dma_alloc_noncontiguous(struct device *dev, size_t size,
+ enum dma_data_direction dir, gfp_t gfp)
+
+This routine allocates bytes of non-coherent and possibly
non-contiguous
+memory. It returns a pointer to struct sg_table that describes the allocated
+and DMA mapped memory, or NULL if the allocation failed. The resulting memory
+can be used for struct page mapped into a scatterlist are suitable for.
+
+The return sg_table is guaranteed to have 1 single DMA mapped segment as
+indicated by sgt->nents, but it might have multiple CPU side segments as
+indicated by sgt->orig_nents.
+
+The dir parameter specified if data is read and/or written by the device,
+see dma_map_single() for details.
+
+The gfp parameter allows the caller to specify the ``GFP_`` flags (see
+kmalloc()) for the allocation, but rejects flags used to specify a memory
+zone such as GFP_DMA or GFP_HIGHMEM.
+
+Before giving the memory to the device, dma_sync_sgtable_for_device() needs
+to be called, and before reading memory written by the device,
+dma_sync_sgtable_for_cpu(), just like for streaming DMA mappings that are
+reused.
+
+::
+
+ void
+ dma_free_noncontiguous(struct device *dev, size_t size,
+ struct sg_table *sgt,
+ enum dma_data_direction dir)
+
+Free memory previously allocated using dma_alloc_noncontiguous(). dev, size,
+and dir must all be the same as those passed into dma_alloc_noncontiguous().
+sgt must be the pointer returned by dma_alloc_noncontiguous().
+
+::
+
+ void *
+ dma_vmap_noncontiguous(struct device *dev, size_t size,
+ struct sg_table *sgt)
+
+Return a contiguous kernel mapping for an allocation returned from
+dma_alloc_noncontiguous(). dev and size must be the same as those passed into
+dma_alloc_noncontiguous(). sgt must be the pointer returned by
+dma_alloc_noncontiguous().
+
+Once a non-contiguous allocation is mapped using this function, the
+flush_kernel_vmap_range() and invalidate_kernel_vmap_range() APIs must be used
+to manage the coherency of the kernel mapping.
+
+::
+
+ void
+ dma_vunmap_noncontiguous(struct device *dev, void *vaddr)
+
+Unmap a kernel mapping returned by dma_vmap_noncontiguous(). dev must be the
+same the one passed into dma_alloc_noncontiguous(). vaddr must be the pointer
+returned by dma_vmap_noncontiguous().
+
+
+::
+
+ int
+ dma_mmap_noncontiguous(struct device *dev, struct vm_area_struct *vma,
+ size_t size, struct sg_table *sgt)
+
+Map an allocation returned from dma_alloc_noncontiguous() into a user address
+space. dev and size must be the same as those passed into
+dma_alloc_noncontiguous(). sgt must be the pointer returned by
+dma_alloc_noncontiguous().
+
::
int
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 11e02537b9e01b..fe46a41130e662 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -22,6 +22,10 @@ struct dma_map_ops {
gfp_t gfp);
void (*free_pages)(struct device *dev, size_t size, struct page *vaddr,
dma_addr_t dma_handle, enum dma_data_direction dir);
+ struct sg_table *(*alloc_noncontiguous)(struct device *dev, size_t size,
+ enum dma_data_direction dir, gfp_t gfp);
+ void (*free_noncontiguous)(struct device *dev, size_t size,
+ struct sg_table *sgt, enum dma_data_direction dir);
int
