After extending v7s, our pagetable already support iova reach
16GB(34bit). the master got the iova via dma_alloc_attrs may reach
34bits, but its HW register still is 32bit. then how to set the
bit32/bit33 iova? this depend on a SMI larb setting(bank_sel).

we separate whole 16GB iova to four banks:
bank: 0: 0~4G; 1: 4~8G; 2: 8-12G; 3: 12-16G;
The bank number is (iova >> 32).

We will preassign which bank the larbs belong to. currently we don't
have a interface for master to adjust its bank number.

Each a bank is a iova_region which is a independent iommu-domain.
the iova range for each iommu-domain can't cross 4G.
Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org> #for memory part
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Link: https://lore.kernel.org/r/20210111111914.22211-31-yong.wu@mediatek.comSigned-off-by: Will Deacon <will@kernel.org>