the rockchip IOMMU is part of the master block in hardware, so it needs
to control the master's power domain and some of the master's clocks
when access it's registers.
and the number of clocks needed here, might be different between each
IOMMUs(according to which master block it belongs), it's a little like
our power domain:
https://elixir.free-electrons.com/linux/latest/source/arch/arm64/boot/dts/rockchip/rk3399.dtsi#L935
i'm not sure how to describe this correctly, is it ok use something like
"the same as it's master block"?
would it make sense to add a property to specify the master who owns
the iommu, and we can get all clocks(only some of those clocks are
actually needed) from it in the of_xlate()? and we can also reuse the
clock-names of that master to build clk_bulk_data and log errors in
clk_bulk_get.
I'm inclined to agree with Rob here - if we're to add anything to the
binding, it should only be whatever clock inputs are defined for the
IOMMU IP block itself. If Linux doesn't properly handle the interconnect
clock hierarchy external to a particular integration, that's a separate
issue and it's not the binding's problem.
I actually quite like the hack of "borrowing" the clocks from
dev->of_node in of_xlate() - you shouldn't need any DT changes for that,
because you already know that each IOMMU instance only has the one
master device anyway.
Robin.