Hi,
This series tries to solve the problem with DMA with device registers
(MMIO registers) that are behind an IOMMU for the rcar-dmac driver. A
recent patch '9575632 (dmaengine: make slave address physical)'
clarifies that DMA slave address provided by clients is the physical
address. This puts the task of mapping the DMA slave address from a
phys_addr_t to a dma_addr_t on the DMA engine.
Without an IOMMU this is easy since the phys_addr_t and dma_addr_t are
the same and no special care is needed. However if you have a IOMMU you
need to map the DMA slave phys_addr_t to a dma_addr_t using something
like this.
This series is based on top of and requires the patches from Robin
Murphy in the tag 'arm/io-pgtable' from the iommu repository at:
git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu.git
It's tested on a Koelsch with CONFIG_IPMMU_VMSA and by enabling the
ipmmu_ds node in r8a7791.dtsi. I verified operation by interacting with
/dev/mmcblk1 and the serial console which both are devices behind the
iommu.
Furthermore I have audited to the best of my ability all call paths
involved to make sure that the dma_addr_t obtained from
dma_map_resource() to is not used in a way where it would be expected
for the mapping to be RAM (have a struct page). Many thanks to Christoph
Hellwig and Laurent Pinchart for there input in this effort.
* drivers/dma/sh/rcar-dmac.c
Once the phys_addr_t is mapped to a dma_addr_t using
dma_map_resource() it is only used to check that the transferee do not
cross 4GB boundaries and then only directly written to HW registers.
* drivers/iommu/iommu.c
- iommu_map()
Check that it's align to min page size or return -EINVAL then calls
domain->ops->map()
* drivers/iommu/ipmmu-vmsa.c
- ipmmu_map()
No logic only calls domain->ops->map()
* drivers/iommu/io-pgtable-arm.c
- arm_lpae_map()
No logic only calls __arm_lpae_map()
- __arm_lpae_map()
No logic only calls arm_lpae_init_pte()
- arm_lpae_init_pte()
Used to get a pte:
pte |= pfn_to_iopte(paddr >> data->pg_shift, data);
* drivers/iommu/io-pgtable-arm-v7s.c
- arm_v7s_map()
No logic only calls __arm_v7s_map()
- __arm_v7s_map()
No logic only calls arm_v7s_init_pte()
- arm_v7s_init_pte
Used to get a pte:
pte |= paddr & ARM_V7S_LVL_MASK(lvl);
* ARM dma-mapping
- dma_unmap_*
Only valid unmap is dma_unmap_resource() all others are an invalid
use case.
- dma_sync_single_*
Invalid use case, memory that is mapped is device memory
- dma_common_mmap() and dma_mmap_attrs()
Invalid use case
- dma_common_get_sgtable() and dma_get_sgtable_attrs()
Invalid use case, only for dma_alloc_* allocated memory,
- dma_mapping_error()
OK
While working on the dma-debug parts of this series I found an unrelated
issue with drivers/iommu/io-pgtable-arm.c and CONFIG_DMA_API_DEBUG on
the Koelsch. I tried to address this in the thread
https://lkml.org/lkml/2016/5/8/33 , however it turned out my solution
was not the correct one. I have not tried to address this further so
running this series with CONFIG_DMA_API_DEBUG will trigger this warning
but is unrelated to this work.
* Changes since v5
- Add dma-debug work which adds a new mapping type for the resource
mapping which correctly can be translated to a physical address.
- Drop patches from Robin Murphy since they now are accepted in the
iommu repository and base the series on that tree instead.
- Add a review tag from Laurent.
* Changes since v4
- Move the mapping from phys_addr_t to dma_addr_t from slave_config to the
prepare calls. This way we know the direction of the mapping and don't have
to use DMA_BIDIRECTIONAL. Thanks Vinod for suggesting this.
- To be clear that the data type for slave addresses are changed add a patch
that only changes the data type to phys_addr_t.
- Fixed up commit messages.
* Changes since v3
- Folded in a fix from Robin to his patch.
- Added a check to make sure dma_map_resource can not be used to map RAM as
pointed out by Robin. I use BUG_ON to enforce this. It might not be the best
method but I saw no other good way since DMA_ERROR_CODE might not be defined
on all platforms.
- Added comment about that DTS changes will disable 2 DMA channels due to a HW
(?) but in the DMAC.
- Dropped the use of dma_attrs, no longer needed.
- Collected Acked-by and Reviewed-by from Laurent.
- Various indentation fix ups.
* Changes since v2
- Drop patch to add dma_{map,unmap}_page_attrs.
- Add dma_{map,unmap}_resource to handle the mapping without involving a
'struct page'. Thanks Laurent and Robin for pointing this out.
- Use size instead of address to keep track of if a mapping exist or not
since addr == 0 is valid. Thanks Laurent.
- Pick up patch from Robin with Laurents ack (hope it's OK for me to
attach the ack?) to add IOMMU_MMIO.
- Fix bug in rcar_dmac_device_config where the error check where
inverted.
- Use DMA_BIDIRECTIONAL in rcar_dmac_device_config since we at that
point can't be sure what direction the mapping is going to be used.
* Changes since v1
- Add and use a dma_{map,unmap}_page_attrs to be able to map the page
using attributes DMA_ATTR_NO_KERNEL_MAPPING and
DMA_ATTR_SKIP_CPU_SYNC. Thanks Laurent.
- Drop check if dmac is part of a iommu group or not, let the DMA
mapping api handle it.
- Move slave configuration data around in rcar-dmac to avoid code
duplication.
- Fix build issue reported by 'kbuild test robot' regarding phys_to_page
not availability on some configurations.
- Add DT information for r8a7791.
* Changes since RFC
- Switch to use the dma-mapping api instead of using the iommu_map()
directly. Turns out the dma-mapper is much smarter then me...
- Dropped the patch to expose domain->ops->pgsize_bitmap from within the
iommu api.
- Dropped the patch showing how I tested the RFC.
Niklas Söderlund (8):
dma-mapping: add {map,unmap}_resource to dma_map_ops
dma-debug: add support for resource mappings
dma-mapping: add dma_{map,unmap}_resource
arm: dma-mapping: add {map,unmap}_resource for iommu ops
dmaengine: rcar-dmac: group slave configuration
dmaengine: rcar-dmac: add iommu support for slave transfers
ARM: dts: r8a7790: add iommus to dmac0 and dmac1
ARM: dts: r8a7791: add iommus to dmac0 and dmac1
Documentation/DMA-API.txt | 22 ++++++--
arch/arm/boot/dts/r8a7790.dtsi | 30 +++++++++++
arch/arm/boot/dts/r8a7791.dtsi | 30 +++++++++++
arch/arm/mm/dma-mapping.c | 63 ++++++++++++++++++++++
drivers/dma/sh/rcar-dmac.c | 116 +++++++++++++++++++++++++++++++++--------
include/linux/dma-debug.h | 19 +++++++
include/linux/dma-mapping.h | 42 +++++++++++++++
lib/dma-debug.c | 52 +++++++++++++++++-
8 files changed, 345 insertions(+), 29 deletions(-)
--
2.8.2
