arm: Kconfig: Explain TFABOOT

The CONFIG_TFABOOT option is more about what U-Boot DOES NOT need to do
than to support some features.

Explain a bit more in the Kconfig help text to avoid misunderstandings.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index abbc89a..2e08e99 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1801,8 +1801,13 @@ config TFABOOT
        depends on ARCH_SUPPORT_TFABOOT
        default n
        help
-         Enabling this will make a U-Boot binary that is capable of being
-         booted via TF-A (Trusted Firmware for Cortex-A).
+         Some platforms support the setup of secure registers (for instance
+         for CPU errata handling) or provide secure services like PSCI.
+         Those services could also be provided by other firmware parts
+         like TF-A (Trusted Firmware for Cortex-A), in which case U-Boot
+         does not need to (and cannot) execute this code.
+         Enabling this option will make a U-Boot binary that is relying
+         on other firmware layers to provide secure functionality.
 
 config TI_SECURE_DEVICE
        bool "HS Device Type Support"