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author | Linus Torvalds <torvalds@linux-foundation.org> | 2012-12-20 10:07:25 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-12-20 10:07:25 -0800 |
commit | 787314c35fbb97e02823a1b8eb8cfa58f366cd49 (patch) | |
tree | 3fe5a484c1846c80361217a726997484533e8344 /Documentation | |
parent | 6491d4d02893d9787ba67279595990217177b351 (diff) | |
parent | 9c6ecf6a3ade2dc4b03a239af68058b22897af41 (diff) | |
download | linux-stable-787314c35fbb97e02823a1b8eb8cfa58f366cd49.tar.gz linux-stable-787314c35fbb97e02823a1b8eb8cfa58f366cd49.tar.bz2 linux-stable-787314c35fbb97e02823a1b8eb8cfa58f366cd49.zip |
Merge tag 'iommu-updates-v3.8' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu
Pull IOMMU updates from Joerg Roedel:
"A few new features this merge-window. The most important one is
probably, that dma-debug now warns if a dma-handle is not checked with
dma_mapping_error by the device driver. This requires minor changes
to some architectures which make use of dma-debug. Most of these
changes have the respective Acks by the Arch-Maintainers.
Besides that there are updates to the AMD IOMMU driver for refactor
the IOMMU-Groups support and to make sure it does not trigger a
hardware erratum.
The OMAP changes (for which I pulled in a branch from Tony Lindgren's
tree) have a conflict in linux-next with the arm-soc tree. The
conflict is in the file arch/arm/mach-omap2/clock44xx_data.c which is
deleted in the arm-soc tree. It is safe to delete the file too so
solve the conflict. Similar changes are done in the arm-soc tree in
the common clock framework migration. A missing hunk from the patch
in the IOMMU tree will be submitted as a seperate patch when the
merge-window is closed."
* tag 'iommu-updates-v3.8' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu: (29 commits)
ARM: dma-mapping: support debug_dma_mapping_error
ARM: OMAP4: hwmod data: ipu and dsp to use parent clocks instead of leaf clocks
iommu/omap: Adapt to runtime pm
iommu/omap: Migrate to hwmod framework
iommu/omap: Keep mmu enabled when requested
iommu/omap: Remove redundant clock handling on ISR
iommu/amd: Remove obsolete comment
iommu/amd: Don't use 512GB pages
iommu/tegra: smmu: Move bus_set_iommu after probe for multi arch
iommu/tegra: gart: Move bus_set_iommu after probe for multi arch
iommu/tegra: smmu: Remove unnecessary PTC/TLB flush all
tile: dma_debug: add debug_dma_mapping_error support
sh: dma_debug: add debug_dma_mapping_error support
powerpc: dma_debug: add debug_dma_mapping_error support
mips: dma_debug: add debug_dma_mapping_error support
microblaze: dma-mapping: support debug_dma_mapping_error
ia64: dma_debug: add debug_dma_mapping_error support
c6x: dma_debug: add debug_dma_mapping_error support
ARM64: dma_debug: add debug_dma_mapping_error support
intel-iommu: Prevent devices with RMRRs from being placed into SI Domain
...
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/DMA-API-HOWTO.txt | 126 | ||||
-rw-r--r-- | Documentation/DMA-API.txt | 12 |
2 files changed, 138 insertions, 0 deletions
diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt index a0b6250add79..4a4fb295ceef 100644 --- a/Documentation/DMA-API-HOWTO.txt +++ b/Documentation/DMA-API-HOWTO.txt @@ -468,11 +468,46 @@ To map a single region, you do: size_t size = buffer->len; dma_handle = dma_map_single(dev, addr, size, direction); + if (dma_mapping_error(dma_handle)) { + /* + * reduce current DMA mapping usage, + * delay and try again later or + * reset driver. + */ + goto map_error_handling; + } and to unmap it: dma_unmap_single(dev, dma_handle, size, direction); +You should call dma_mapping_error() as dma_map_single() could fail and return +error. Not all dma implementations support dma_mapping_error() interface. +However, it is a good practice to call dma_mapping_error() interface, which +will invoke the generic mapping error check interface. Doing so will ensure +that the mapping code will work correctly on all dma implementations without +any dependency on the specifics of the underlying implementation. Using the +returned address without checking for errors could result in failures ranging +from panics to silent data corruption. Couple of example of incorrect ways to +check for errors that make assumptions about the underlying dma implementation +are as follows and these are applicable to dma_map_page() as well. + +Incorrect example 1: + dma_addr_t dma_handle; + + dma_handle = dma_map_single(dev, addr, size, direction); + if ((dma_handle & 0xffff != 0) || (dma_handle >= 0x1000000)) { + goto map_error; + } + +Incorrect example 2: + dma_addr_t dma_handle; + + dma_handle = dma_map_single(dev, addr, size, direction); + if (dma_handle == DMA_ERROR_CODE) { + goto map_error; + } + You should call dma_unmap_single when the DMA activity is finished, e.g. from the interrupt which told you that the DMA transfer is done. @@ -489,6 +524,14 @@ Specifically: size_t size = buffer->len; dma_handle = dma_map_page(dev, page, offset, size, direction); + if (dma_mapping_error(dma_handle)) { + /* + * reduce current DMA mapping usage, + * delay and try again later or + * reset driver. + */ + goto map_error_handling; + } ... @@ -496,6 +539,12 @@ Specifically: Here, "offset" means byte offset within the given page. +You should call dma_mapping_error() as dma_map_page() could fail and return +error as outlined under the dma_map_single() discussion. + +You should call dma_unmap_page when the DMA activity is finished, e.g. +from the interrupt which told you that the DMA transfer is done. + With scatterlists, you map a region gathered from several regions by: int i, count = dma_map_sg(dev, sglist, nents, direction); @@ -578,6 +627,14 @@ to use the dma_sync_*() interfaces. dma_addr_t mapping; mapping = dma_map_single(cp->dev, buffer, len, DMA_FROM_DEVICE); + if (dma_mapping_error(dma_handle)) { + /* + * reduce current DMA mapping usage, + * delay and try again later or + * reset driver. + */ + goto map_error_handling; + } cp->rx_buf = buffer; cp->rx_len = len; @@ -658,6 +715,75 @@ failure can be determined by: * delay and try again later or * reset driver. */ + goto map_error_handling; + } + +- unmap pages that are already mapped, when mapping error occurs in the middle + of a multiple page mapping attempt. These example are applicable to + dma_map_page() as well. + +Example 1: + dma_addr_t dma_handle1; + dma_addr_t dma_handle2; + + dma_handle1 = dma_map_single(dev, addr, size, direction); + if (dma_mapping_error(dev, dma_handle1)) { + /* + * reduce current DMA mapping usage, + * delay and try again later or + * reset driver. + */ + goto map_error_handling1; + } + dma_handle2 = dma_map_single(dev, addr, size, direction); + if (dma_mapping_error(dev, dma_handle2)) { + /* + * reduce current DMA mapping usage, + * delay and try again later or + * reset driver. + */ + goto map_error_handling2; + } + + ... + + map_error_handling2: + dma_unmap_single(dma_handle1); + map_error_handling1: + +Example 2: (if buffers are allocated a loop, unmap all mapped buffers when + mapping error is detected in the middle) + + dma_addr_t dma_addr; + dma_addr_t array[DMA_BUFFERS]; + int save_index = 0; + + for (i = 0; i < DMA_BUFFERS; i++) { + + ... + + dma_addr = dma_map_single(dev, addr, size, direction); + if (dma_mapping_error(dev, dma_addr)) { + /* + * reduce current DMA mapping usage, + * delay and try again later or + * reset driver. + */ + goto map_error_handling; + } + array[i].dma_addr = dma_addr; + save_index++; + } + + ... + + map_error_handling: + + for (i = 0; i < save_index; i++) { + + ... + + dma_unmap_single(array[i].dma_addr); } Networking drivers must call dev_kfree_skb to free the socket buffer diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index 66bd97a95f10..78a6c569d204 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt @@ -678,3 +678,15 @@ out of dma_debug_entries. These entries are preallocated at boot. The number of preallocated entries is defined per architecture. If it is too low for you boot with 'dma_debug_entries=<your_desired_number>' to overwrite the architectural default. + +void debug_dmap_mapping_error(struct device *dev, dma_addr_t dma_addr); + +dma-debug interface debug_dma_mapping_error() to debug drivers that fail +to check dma mapping errors on addresses returned by dma_map_single() and +dma_map_page() interfaces. This interface clears a flag set by +debug_dma_map_page() to indicate that dma_mapping_error() has been called by +the driver. When driver does unmap, debug_dma_unmap() checks the flag and if +this flag is still set, prints warning message that includes call trace that +leads up to the unmap. This interface can be called from dma_mapping_error() +routines to enable dma mapping error check debugging. + |