Re: [PATCH v1 1/3] gpu: host1x: Remove implicit IOMMU backing on client's registration

[Dmitry Osipenko]

24.06.2019 10:04, Christoph Hellwig ÐÐÑÐÑ:
> Don't we have a device tree problem here if there is a domain covering
> them?  I though we should only pick up an IOMMU for a given device
> if DT explicitly asked for that?
> 

There is no specific domain that "covering them". The IOMMU domain is allocated
dynamically during of the Tegra DRM's driver initialization (see tegra_drm_load) and
then all of DRM devices are attached to that domain once all of the DRM sub-drivers
are probed successfully. On Tegra SoCs it's up to software (driver) to decide how to
separate hardware devices from each other, in a case of DRM we're putting all the
relevant graphics devices into a single domain. Is it even possible to express IOMMU
domain (not group!) assignments in a device-tree?