Hello,
On 2014-09-01 13:56, Arnd Bergmann wrote:
On Monday 01 September 2014 12:47:08 Marek Szyprowski wrote:
Who do you think needs to set this flag, and who needs to read it?
In the proposed solution Exynos IOMMU driver creates a separate IO
address space
for every client device in a system and binds it to the default
dma-mapping space
for the given device. When drivers are doing its own management of IO
address
space, instead of relying on what is available by default with dma-mapping
interface, this will require releasing of the previously created default
structures and resources. So this flag is set by the driver doing its own
management of io address space. The flags is then checked by Exynos
IOMMU driver
to avoid creating the default dma-mapping address space for devices
which driver
does its own management.
I don't completely understand it yet. I would assume the device
to be added to the default domain at device creation time
(of_platform_populate), way before we know which device driver
is going to be used. How can this prevent the iommu driver
from doing the association with the domain?
of_platform_populate() is too early to do the association, because that
time the
exynos iommu driver is even not yet probed.
The association with default dma-mapping domain is done in
IOMMU_GROUP_NOTIFY_BIND_DRIVER notifier, just before binding the driver
to the
given device. This way iommu driver can check dev->driver->flags and
skip creating
default dma-mapping domain if driver announces that it wants to handle it by
itself.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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