linux-toradex.git/drivers/memory/tegra, branch v4.1.10 Linux kernel for Apalis and Colibri modules iommu/tegra-smmu: Parameterize number of TLB lines 2015-09-29T17:26:14+00:00 Thierry Reding treding@nvidia.com 2015-08-06T12:20:31+00:00 1f398b31044845397b5e2fefdb7ac247180e6a7c commit 11cec15bf3fb498206ef63b1fa26c27689e02d0e upstream. The number of TLB lines was increased from 16 on Tegra30 to 32 on Tegra114 and later. Parameterize the value so that the initial default can be set accordingly. On Tegra30, initializing the value to 32 would effectively disable the TLB and hence cause massive latencies for memory accesses translated through the SMMU. This is especially noticeable for isochronuous clients such as display, whose FIFOs would continuously underrun. Fixes: 891846516317 ("memory: Add NVIDIA Tegra memory controller support") Signed-off-by: Thierry Reding <treding@nvidia.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 11cec15bf3fb498206ef63b1fa26c27689e02d0e upstream.

The number of TLB lines was increased from 16 on Tegra30 to 32 on
Tegra114 and later. Parameterize the value so that the initial default
can be set accordingly.

On Tegra30, initializing the value to 32 would effectively disable the
TLB and hence cause massive latencies for memory accesses translated
through the SMMU. This is especially noticeable for isochronuous clients
such as display, whose FIFOs would continuously underrun.

Fixes: 891846516317 ("memory: Add NVIDIA Tegra memory controller support")
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
memory: Add NVIDIA Tegra memory controller support 2014-12-04T15:11:47+00:00 Thierry Reding treding@nvidia.com 2014-04-16T07:24:44+00:00 8918465163171322c77a19d5258a95f56d89d2e4 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: Joerg Roedel <jroedel@suse.de> Signed-off-by: Thierry Reding <treding@nvidia.com> 
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: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>