[PATCH v3 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU
Vladimir Murzin
vladimir.murzin at arm.com
Wed Mar 29 01:17:14 PDT 2017
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 <vladimir.murzin at arm.com> 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 <jroedel at suse.de>
>>>> Cc: Christian Borntraeger <borntraeger at de.ibm.com>
>>>> Cc: Michal Nazarewicz <mina86 at mina86.com>
>>>> Cc: Marek Szyprowski <m.szyprowski at samsung.com>
>>>> Cc: Alan Stern <stern at rowland.harvard.edu>
>>>> Cc: Yoshinori Sato <ysato at users.sourceforge.jp>
>>>> Cc: Rich Felker <dalias at libc.org>
>>>> Cc: Roger Quadros <rogerq at ti.com>
>>>> Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
>>>> Cc: Rob Herring <robh+dt at kernel.org>
>>>> Cc: Mark Rutland <mark.rutland at arm.com>
>>>> Cc: Doug Ledford <dledford at redhat.com>
>>>>
>>>> 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
>>>>
>>>
>>
>>
>
>
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