arm64: spin-table: add more information in Kconfig help
This feature seems to be sometimes misunderstood. The intention is:
[1] Bring the slaves into the U-Boot proper image, not SPL (unless
you have a special reason to do otherwise).
[2] The operation must be done in a board (SoC) specific manner
since how to wake the slaves from the Boot ROM is SoC specific.
[3] The slaves must enter U-Boot proper after U-Boot relocates
itself because the "cpu-release-addr" property points to the
relocated memory area.
[2] is already explained in the help. We can make [1] even clearer
by mentioning "U-Boot proper" instead of "U-Boot". [3] is missing,
so I am adding it to the list. Instead, "before the master CPU
jumps to the kernel" is a matter of course, so removed.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/arch/arm/cpu/armv8/Kconfig b/arch/arm/cpu/armv8/Kconfig
index 0b3d98e..0188b95 100644
--- a/arch/arm/cpu/armv8/Kconfig
+++ b/arch/arm/cpu/armv8/Kconfig
@@ -30,8 +30,10 @@
To use this feature, you must do:
- Specify enable-method = "spin-table" in each CPU node in the
Device Tree you are using to boot the kernel
- - Let secondary CPUs in U-Boot (in a board specific manner)
- before the master CPU jumps to the kernel
+ - Bring secondary CPUs into U-Boot proper in a board specific
+ manner. This must be done *after* relocation. Otherwise, the
+ secondary CPUs will spin in unprotected memory area because the
+ master CPU protects the relocated spin code.
U-Boot automatically does:
- Set "cpu-release-addr" property of each CPU node