From 73c38934daa10b518b20f2d21298fc8a8226843b Mon Sep 17 00:00:00 2001 From: Stephen Warren Date: Mon, 19 Jan 2015 16:25:52 -0700 Subject: 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 Signed-off-by: Tom Warren --- arch/arm/include/asm/arch-tegra/ap.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'arch/arm/include/asm/arch-tegra') diff --git a/arch/arm/include/asm/arch-tegra/ap.h b/arch/arm/include/asm/arch-tegra/ap.h index 5c8be94d97..ca40e4e0bc 100644 --- a/arch/arm/include/asm/arch-tegra/ap.h +++ b/arch/arm/include/asm/arch-tegra/ap.h @@ -74,3 +74,7 @@ static inline void config_vpr(void) { } #endif + +#if defined(CONFIG_TEGRA_SUPPORT_NON_SECURE) +bool tegra_cpu_is_non_secure(void); +#endif -- cgit v1.2.1