Well, I've no objection to this, but it does need acks from other people before I can apply it.
There's two patches that touch drivers/base that need Greg's ack. I'm not sure what's happening with lib/dma-noop.c, there doesn't appear to be a maintainer list for it, so I guess that's a free-for-all. On Thu, Jun 08, 2017 at 09:28:30AM +0100, Vladimir Murzin wrote: > Ping! > > On 24/05/17 11:24, Vladimir Murzin wrote: > > Short story: > > > > Without these patches coherent DMA is broken for András and Alexandre, > > so they cannot safely enable DMA on their platforms. > > > > Patches have been circulated on a list since last year without much > > attention to changes in dma-coherent.c and dma-noop.c. Meanwhile, ARM > > bits have been reviewed and there is no strict objection to get them > > merged. Unfortunately, applying only ARM bits doesn't help much and > > the original issue would still exist. > > > > Please, let me know how to move with this fix forward? > > > > Long story: > > > > It seems 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 versions 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 any 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 at 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: > > v4 -> v5 > > - rebased on v4.12-rc2 > > - updated description for CONFIG_ARM_DMA_MEM_BUFFERABLE > > > > v3 -> v4 > > - rebased on v4.11-rc7 > > - made CONFIG_ARM_DMA_MEM_BUFFERABLE optional for CPU_V7M > > - added Arnd's Acked-by > > > > 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 | 8 +- > > 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, 359 insertions(+), 45 deletions(-) > > create mode 100644 arch/arm/mm/dma-mapping-nommu.c > > > -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
