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/rk3399_rockchip-uboot/arch/arm/mach-tegra/
H A Dboard2.c00f782a9f82a20b2fe4bf6c254758e6ac94ddb15 Mon Jul 27 17:45:24 UTC 2015 Thierry Reding <treding@nvidia.com> ARM: tegra: Restrict usable RAM to 32-bit on 64-bit SoCs

Most peripherals on Tegra can do DMA only to the lower 32-bit
address space, even on 64-bit SoCs. This limitation is
typically overcome by the use of an IOMMU. Since the IOMMU is
not entirely trivial to set up and serves no other purpose
(I/O protection, ...) in U-Boot, restrict 64-bit Tegra SoCs to
the lower 32-bit address space for RAM. This ensures that the
physical addresses of buffers that are programmed into the
various DMA engines are valid and don't alias to lower addresses.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>