Re: [RFC 0/6] iommu: generic api migration and grouping

Kyungmin Park
2011-06-02T23:57:06Z

Hi,

Good approach.
CC'ed the Samsung IOMMU developer. Marek.

BTW, Russell wants to use the DMA based IOMMU?

Please see the RFC patch, ARM: DMA-mapping & IOMMU integration
http://www.spinics.net/lists/linux-mm/msg19856.html

Thank you,
Kyungmin Park

On Fri, Jun 3, 2011 at 7:27 AM, Ohad Ben-Cohen <ohad@wizery.com> wrote:
> First stab at iommu consolidation:
>
> - Migrate OMAP's iommu driver to the generic iommu API. With this in hand,
>  users can now start using the generic iommu layer instead of calling
>  omap-specific iommu API.
>
>  New code that requires functionality missing from the generic iommu api,
>  will add that functionality in the generic framework (e.g. adding framework
>  awareness to multi page sizes, supported by the underlying hardware, will
>  avoid the otherwise-inevitable code duplication when mapping a memory
>  region).
>
>  OMAP-specific api that is still exposed in the omap iommu driver can
>  now be either moved to the generic iommu framework, or just removed (if not
>  used).
>
>  This api (and other omap-specific primitives like struct iommu) needs to
>  be omapified (i.e. renamed to include an 'omap_' prefix). At this early
>  point of this patch set this is too much churn though, so I'll do that
>  in the following iteration, after (and if), the general direction is
>  accepted.
>
> - Migrate OMAP's iovmm (virtual memory manager) driver to the generic
>  iommu API. With this in hand, iovmm no longer uses omap-specific api
>  for mapping/unmapping operations. Nevertheless, iovmm is still coupled
>  with omap's iommu even with this change: it assumes omap page sizes,
>  and it uses omap's iommu objects to maintain its internal state.
>
>  Further generalizing of iovmm strongly depends on our broader plans for
>  providing a generic virtual memory manager and allocation framework
>  (which, as discussed, should be separated from a specific mapper).
>
>  iovmm has a mainline user: omap3isp, and therefore must be maintained,
>  but new potential users will either have to generalize it, or come up
>  with a different generic framework that will replace it.
>
> - Migrate OMAP's iommu mainline user, omap3isp, to the generic API as well
>  (so it doesn't break). As with iovmm, omap3isp still depends on
>  omap's iommu, mainly because iovmm depends on it, but also for
>  iommu context saving and restoring.
>
>  It is definitely desirable to completely remove omap3isp's dependency
>  on the omap-specific iommu layer, and that will be possible as the
>  required functionality will be added to generic framework.
>
> - Create a dedicated iommu drivers folder (and put the base iommu code there)
> - Move OMAP's and MSM's iommu drivers to that drivers iommu folder
>
>  Putting all iommu drivers together will ease finding similarities
>  between different platforms, with the intention of solving problems once,
>  in a generic framework which everyone can use.
>
>  I've only moved the omap and msm implementations for now, to demonstrate
>  the idea (and support the ARM diet :), but if this is found desirable,
>  we can bring in intel-iommu.c and amd_iommu.c as well.
>
> Meta:
>
> - This patch set is not bisectable; it was splitted (and ordered) this way
>  to ease its review. Later iterations of this patch set will fix that
>  (most likely by squashing the first three patches)
> - Based on and tested with 3.0-rc1
> - OMAP's iommu code was tested on both OMAP3 and OMAP4
> - omap3isp code was tested with a sensor-less OMAP3 (memory-to-memory only)
>  (thanks Laurent Pinchart for showing me the magic needed to test omap3isp :)
> - MSM code was only compile tested
>
> Ohad Ben-Cohen (6):
>  omap: iommu: generic iommu api migration
>  omap: iovmm: generic iommu api migration
>  media: omap3isp: generic iommu api migration
>  drivers: iommu: move to a dedicated folder
>  omap: iommu/iovmm: move to dedicated iommu folder
>  msm: iommu: move to dedicated iommu drivers folder
>
>  arch/arm/mach-msm/Kconfig                          |   15 -
>  arch/arm/mach-msm/Makefile                         |    2 +-
>  arch/arm/plat-omap/Kconfig                         |   12 -
>  arch/arm/plat-omap/Makefile                        |    2 -
>  arch/arm/plat-omap/include/plat/iommu.h            |    3 +-
>  arch/arm/plat-omap/{ => include/plat}/iopgtable.h  |   18 ++
>  arch/arm/plat-omap/include/plat/iovmm.h            |   27 +-
>  arch/x86/Kconfig                                   |    5 +-
>  drivers/Kconfig                                    |    2 +
>  drivers/Makefile                                   |    1 +
>  drivers/base/Makefile                              |    1 -
>  drivers/iommu/Kconfig                              |   32 +++
>  drivers/iommu/Makefile                             |    5 +
>  drivers/{base => iommu}/iommu.c                    |    0
>  .../mach-msm/iommu.c => drivers/iommu/msm-iommu.c  |    0
>  .../iommu/omap-iommu-debug.c                       |    2 +-
>  .../iommu.c => drivers/iommu/omap-iommu.c          |  290 +++++++++++++++++---
>  .../iovmm.c => drivers/iommu/omap-iovmm.c          |  113 +++++---
>  drivers/media/video/Kconfig                        |    2 +-
>  drivers/media/video/omap3isp/isp.c                 |   41 +++-
>  drivers/media/video/omap3isp/isp.h                 |    3 +
>  drivers/media/video/omap3isp/ispccdc.c             |   16 +-
>  drivers/media/video/omap3isp/ispstat.c             |    6 +-
>  drivers/media/video/omap3isp/ispvideo.c            |    4 +-
>  24 files changed, 451 insertions(+), 151 deletions(-)
>  rename arch/arm/plat-omap/{ => include/plat}/iopgtable.h (84%)
>  create mode 100644 drivers/iommu/Kconfig
>  create mode 100644 drivers/iommu/Makefile
>  rename drivers/{base => iommu}/iommu.c (100%)
>  rename arch/arm/mach-msm/iommu.c => drivers/iommu/msm-iommu.c (100%)
>  rename arch/arm/plat-omap/iommu-debug.c => drivers/iommu/omap-iommu-debug.c (99%)
>  rename arch/arm/plat-omap/iommu.c => drivers/iommu/omap-iommu.c (77%)
>  rename arch/arm/plat-omap/iovmm.c => drivers/iommu/omap-iovmm.c (85%)
>
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