Re: [PATCH 10/29] drivers: add DRIVER_HAS_OWN_IOMMU_MANAGER flag

Arnd Bergmann
2014-09-01T11:57:11Z

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?

Arnd