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author | Stephen Warren <swarren@nvidia.com> | 2015-01-19 16:25:52 -0700 |
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committer | Tom Warren <twarren@nvidia.com> | 2015-03-04 10:08:57 -0700 |
commit | 73c38934daa10b518b20f2d21298fc8a8226843b (patch) | |
tree | 68d0f8837373d2fce809f7e38bb4ff89f14558b9 /board/miromico | |
parent | 026baff755cbab0c8bfc12d78e6966718f5325a5 (diff) | |
download | u-boot-imx-73c38934daa10b518b20f2d21298fc8a8226843b.zip u-boot-imx-73c38934daa10b518b20f2d21298fc8a8226843b.tar.gz u-boot-imx-73c38934daa10b518b20f2d21298fc8a8226843b.tar.bz2 |
ARM: tegra: support running in non-secure mode
When the CPU is in non-secure (NS) mode (when running U-Boot under a
secure monitor), certain actions cannot be taken, since they would need
to write to secure-only registers. One example is configuring the ARM
architectural timer's CNTFRQ register.
We could support this in one of two ways:
1) Compile twice, once for secure mode (in which case anything goes) and
once for non-secure mode (in which case certain actions are disabled).
This complicates things, since everyone needs to keep track of
different U-Boot binaries for different situations.
2) Detect NS mode at run-time, and optionally skip any impossible actions.
This has the advantage of a single U-Boot binary working in all cases.
(2) is not possible on ARM in general, since there's no architectural way
to detect secure-vs-non-secure. However, there is a Tegra-specific way to
detect this.
This patches uses that feature to detect secure vs. NS mode on Tegra, and
uses that to:
* Skip the ARM arch timer initialization.
* Set/clear an environment variable so that boot scripts can take
different action depending on which mode the CPU is in. This might be
something like:
if CPU is secure:
load secure monitor code into RAM.
boot secure monitor.
secure monitor will restart (a new copy of) U-Boot in NS mode.
else:
execute normal boot process
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
Diffstat (limited to 'board/miromico')
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