Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1660928 > unrolled thread
| Started by | Vladimir Murzin <vladimir.murzin@arm.com> |
|---|---|
| First post | 2017-06-08 10:30 +0200 |
| Last post | 2017-06-15 09:30 +0200 |
| Articles | 3 — 2 participants |
Back to article view | Back to linux.kernel
This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by
below is the oldest one visible, not the original post.
Re: [PATCH v5 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU Vladimir Murzin <vladimir.murzin@arm.com> - 2017-06-08 10:30 +0200
Re: [PATCH v5 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-06-08 18:30 +0200
Re: [PATCH v5 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU Vladimir Murzin <vladimir.murzin@arm.com> - 2017-06-15 09:30 +0200
| From | Vladimir Murzin <vladimir.murzin@arm.com> |
|---|---|
| Date | 2017-06-08 10:30 +0200 |
| Subject | Re: [PATCH v5 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU |
| Message-ID | <tQ0Zk-1Oi-11@gated-at.bofh.it> |
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 <jroedel@suse.de> > Cc: Christian Borntraeger <borntraeger@de.ibm.com> > Cc: Michal Nazarewicz <mina86@mina86.com> > Cc: Marek Szyprowski <m.szyprowski@samsung.com> > Cc: Alan Stern <stern@rowland.harvard.edu> > Cc: Yoshinori Sato <ysato@users.sourceforge.jp> > Cc: Rich Felker <dalias@libc.org> > Cc: Roger Quadros <rogerq@ti.com> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Rob Herring <robh+dt@kernel.org> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: Doug Ledford <dledford@redhat.com> > > 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 >
[toc] | [next] | [standalone]
| From | Russell King - ARM Linux <linux@armlinux.org.uk> |
|---|---|
| Date | 2017-06-08 18:30 +0200 |
| Message-ID | <tQ8tR-6AH-29@gated-at.bofh.it> |
| In reply to | #1660928 |
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 <jroedel@suse.de> > > Cc: Christian Borntraeger <borntraeger@de.ibm.com> > > Cc: Michal Nazarewicz <mina86@mina86.com> > > Cc: Marek Szyprowski <m.szyprowski@samsung.com> > > Cc: Alan Stern <stern@rowland.harvard.edu> > > Cc: Yoshinori Sato <ysato@users.sourceforge.jp> > > Cc: Rich Felker <dalias@libc.org> > > Cc: Roger Quadros <rogerq@ti.com> > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > Cc: Rob Herring <robh+dt@kernel.org> > > Cc: Mark Rutland <mark.rutland@arm.com> > > Cc: Doug Ledford <dledford@redhat.com> > > > > 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.
[toc] | [prev] | [next] | [standalone]
| From | Vladimir Murzin <vladimir.murzin@arm.com> |
|---|---|
| Date | 2017-06-15 09:30 +0200 |
| Message-ID | <tSxo5-7X3-9@gated-at.bofh.it> |
| In reply to | #1661463 |
Greg? On 08/06/17 17:25, Russell King - ARM Linux wrote: > 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 <jroedel@suse.de> >>> Cc: Christian Borntraeger <borntraeger@de.ibm.com> >>> Cc: Michal Nazarewicz <mina86@mina86.com> >>> Cc: Marek Szyprowski <m.szyprowski@samsung.com> >>> Cc: Alan Stern <stern@rowland.harvard.edu> >>> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> >>> Cc: Rich Felker <dalias@libc.org> >>> Cc: Roger Quadros <rogerq@ti.com> >>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> >>> Cc: Rob Herring <robh+dt@kernel.org> >>> Cc: Mark Rutland <mark.rutland@arm.com> >>> Cc: Doug Ledford <dledford@redhat.com> >>> >>> 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 >>> >> >
[toc] | [prev] | [standalone]
Back to top | Article view | linux.kernel
csiph-web