• Thierry Reding's avatar
    memory: Add NVIDIA Tegra memory controller support · 89184651
    Thierry Reding authored
    The memory controller on NVIDIA Tegra exposes various knobs that can be
    used to tune the behaviour of the clients attached to it.
    
    Currently this driver sets up the latency allowance registers to the HW
    defaults. Eventually an API should be exported by this driver (via a
    custom API or a generic subsystem) to allow clients to register latency
    requirements.
    
    This driver also registers an IOMMU (SMMU) that's implemented by the
    memory controller. It is supported on Tegra30, Tegra114 and Tegra124
    currently. Tegra20 has a GART instead.
    
    The Tegra SMMU operates on memory clients and SWGROUPs. A memory client
    is a unidirectional, special-purpose DMA master. A SWGROUP represents a
    set of memory clients that form a logical functional unit corresponding
    to a single device. Typically a device has two clients: one client for
    read transactions and one client for write transactions, but there are
    also devices that have only read clients, but many of them (such as the
    display controllers).
    
    Because there is no 1:1 relationship between memory clients and devices
    the driver keeps a table of memory clients and the SWGROUPs that they
    belong to per SoC. Note that this is an exception and due to the fact
    that the SMMU is tightly integrated with the rest of the Tegra SoC. The
    use of these tables is discouraged in drivers for generic IOMMU devices
    such as the ARM SMMU because the same IOMMU could be used in any number
    of SoCs and keeping such tables for each SoC would not scale.
    Acked-by: default avatarJoerg Roedel <jroedel@suse.de>
    Signed-off-by: default avatarThierry Reding <treding@nvidia.com>
    89184651
tegra-smmu.c 16.5 KB