Ping! On 23/03/17 09:26, Vladimir Murzin wrote: > 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 >>>> >>> >> >> > > > _______________________________________________ > linux-arm-kernel mailing list > [email protected] > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
