On 22/03/17 12:23, Szemző András wrote: > I’ve tested this v3 version on my Atmel armv7m board with several drivers > with DMA and enabled caches, > and I’ve not seen any issues. > > You can add my Tested-by.
Much appreciated! Russell, Andrew, Greg, any advise on how to get this series merged? Patches has been circulated on a list since December last year and without them András and Alexandre cannot safely enable DMA on their platforms. Cheers Vladimir > > Thanks for the patches! > > Andras > >> On 2017. Mar 16., at 10:03, Vladimir Murzin <[email protected]> wrote: >> >> Gentle ping! >> >> On 10/03/17 09:23, Vladimir Murzin wrote: >>> It seem that addition of cache support for M-class CPUs uncovered >>> latent bug in DMA usage. NOMMU memory model has been treated as being >>> always consistent; however, for R/M CPU classes memory can be covered >>> by MPU which in turn might configure RAM as Normal i.e. bufferable and >>> cacheable. It breaks dma_alloc_coherent() and friends, since data can >>> stuck in caches now or be buffered. >>> >>> This patch set is trying to address the issue by providing region of >>> memory suitable for consistent DMA operations. It is supposed that >>> such region is marked by MPU as non-cacheable. Robin suggested to >>> advertise such memory as reserved shared-dma-pool, rather then using >>> homebrew command line option, and extend dma-coherent to provide >>> default DMA area in the similar way as it is done for CMA (PATCH >>> 4/7). It allows us to offload all bookkeeping on generic coherent DMA >>> framework, and it seems that it might be reused by other architectures >>> like c6x and blackfin. >>> >>> While reviewing/testing previous vesrions of the patch set it turned >>> out that dma-coherent does not take into account "dma-ranges" device >>> tree property, so it is addressed in PATCH 3/7. >>> >>> For ARM, dedicated DMA region is required for cases other than: >>> - MMU/MPU is off >>> - cpu is v7m w/o cache support >>> - device is coherent >>> >>> In case one of the above conditions is true dma operations are forced >>> to be coherent and wired with dma_noop_ops. >>> >>> To make life easier NOMMU dma operations are kept in separate >>> compilation unit. >>> >>> Since the issue was reported in the same time as Benjamin sent his >>> patch [1] to allow mmap for NOMMU, his case is also addressed in this >>> series (PATCH 1/7 and PATCH 2/7). >>> >>> Thanks! >>> >>> [1] http://www.armlinux.org.uk/developer/patches/viewpatch.php?id=8633/1 >>> >>> Cc: Joerg Roedel <[email protected]> >>> Cc: Christian Borntraeger <[email protected]> >>> Cc: Michal Nazarewicz <[email protected]> >>> Cc: Marek Szyprowski <[email protected]> >>> Cc: Alan Stern <[email protected]> >>> Cc: Yoshinori Sato <[email protected]> >>> Cc: Rich Felker <[email protected]> >>> Cc: Roger Quadros <[email protected]> >>> Cc: Greg Kroah-Hartman <[email protected]> >>> Cc: Rob Herring <[email protected]> >>> Cc: Mark Rutland <[email protected]> >>> Cc: Doug Ledford <[email protected]> >>> >>> Changelog: >>> v2 -> v3 >>> - fixed warnings reported by Alexandre and kbuild robot >>> >>> v1 -> v2 >>> - rebased on v4.11-rc1 >>> - added Robin's Reviewed-by >>> - dedicated flag is introduced to use dev->dma_pfn_offset >>> rather than mem->device_base in case memory region is >>> configured via device tree (so Tested-by discarded there) >>> >>> RFC v6 -> v1 >>> - dropped RFC tag >>> - added Alexandre's Tested-by >>> >>> Vladimir Murzin (7): >>> dma: Take into account dma_pfn_offset >>> dma: Add simple dma_noop_mmap >>> drivers: dma-coherent: Account dma_pfn_offset when used with device >>> tree >>> drivers: dma-coherent: Introduce default DMA pool >>> ARM: NOMMU: Introduce dma operations for noMMU >>> ARM: NOMMU: Set ARM_DMA_MEM_BUFFERABLE for M-class cpus >>> ARM: dma-mapping: Remove traces of NOMMU code >>> >>> .../bindings/reserved-memory/reserved-memory.txt | 3 + >>> arch/arm/Kconfig | 1 + >>> arch/arm/include/asm/dma-mapping.h | 2 +- >>> arch/arm/mm/Kconfig | 2 +- >>> arch/arm/mm/Makefile | 5 +- >>> arch/arm/mm/dma-mapping-nommu.c | 253 >>> +++++++++++++++++++++ >>> arch/arm/mm/dma-mapping.c | 29 +-- >>> drivers/base/dma-coherent.c | 74 +++++- >>> lib/dma-noop.c | 29 ++- >>> 9 files changed, 354 insertions(+), 44 deletions(-) >>> create mode 100644 arch/arm/mm/dma-mapping-nommu.c >>> >> > >
