ARM: tegra: Select appropriate DMA options for LPAE

This automatically selects options for zone DMA and 64 bit DMA addresses
when LPAE is enabled on ARM Tegra platforms. These options are required
for proper operation with LPAE enabled.

The ZONE_DMA option is required to ensure that drivers that allocate DMA
memory get buffers from the first 4 GiB. This is necessary because a lot
of the controllers only support addressing 32 bits.

As for ARCH_DMA_ADDR_T_64BIT, there are situations where devices that do
support addresses of more than 32 bits (such as the display controller
or the GPU) can run without translating addresses through an IOMMU on a
device with more than 4 GiB of system memory.

Note that both of these options are stop-gap solutions required only
until the IOMMU can be properly integrated with the DMA mapping API and
drivers use that properly and consistently.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
[treding@nvidia.com: specify rationale for options]
Signed-off-by: Thierry Reding <treding@nvidia.com>
(backported from commit 6aa26c5d66595494e810c791602d87a572c78808)

diff --git a/arch/arm/mach-tegra/Kconfig b/arch/arm/mach-tegra/Kconfig
index ac1d33bd97fbd8d2345b5bfc68fd6098c269cb12..8385f1f30acaeae17e7ebe4b26083621c3267ab8 100644 (file)
--- a/arch/arm/mach-tegra/Kconfig
+++ b/arch/arm/mach-tegra/Kconfig
@@ -107,6 +107,8 @@ config ARCH_TEGRA_12x_SOC
        select TEGRA_ISOMGR
        select TEGRA_ISOMGR_SYSFS
        select PROC_DEVICETREE
+    select ZONE_DMA if ARM_LPAE
+    select ARCH_DMA_ADDR_T_64BIT if ARM_LPAE
        help
          Support for NVIDIA Tegra 12x family of SoCs, based upon the
          ARM Cortex-A15MP CPU