arm64: add better and more generic spin-table support
There are two enable methods supported by ARM64 Linux; psci and
spin-table. The latter is simpler and helpful for quick SoC bring
up. My main motivation for this patch is to improve the spin-table
support, which allows us to boot an ARMv8 system without the ARM
Trusted Firmware.
Currently, we have multi-entry code in arch/arm/cpu/armv8/start.S
and the spin-table is supported in a really ad-hoc way, and I see
some problems:
- We must hard-code CPU_RELEASE_ADDR so that it matches the
"cpu-release-addr" property in the DT that comes from the
kernel tree.
- The Documentation/arm64/booting.txt in Linux requires that
the release address must be zero-initialized, but it is not
cared by the common code in U-Boot. We must do it in a board
function.
- There is no systematic way to protect the spin-table code from
the kernel. We are supposed to do it in a board specific manner,
but it is difficult to predict where the spin-table code will be
located after the relocation. So, it also makes difficult to
hard-code /memreserve/ in the DT of the kernel.
So, here is a patch to solve those problems; the DT is run-time
modified to reserve the spin-table code (+ cpu-release-addr).
Also, the "cpu-release-addr" property is set to an appropriate
address after the relocation, which means we no longer need the
hard-coded CPU_RELEASE_ADDR.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
index 670e323..67edf94 100644
--- a/arch/arm/cpu/armv8/start.S
+++ b/arch/arm/cpu/armv8/start.S
@@ -94,7 +94,11 @@
/* Processor specific initialization */
bl lowlevel_init
-#ifdef CONFIG_ARMV8_MULTIENTRY
+#if CONFIG_IS_ENABLED(ARMV8_SPIN_TABLE)
+ branch_if_master x0, x1, master_cpu
+ b spin_table_secondary_jump
+ /* never return */
+#elif defined(CONFIG_ARMV8_MULTIENTRY)
branch_if_master x0, x1, master_cpu
/*
@@ -106,10 +110,8 @@
ldr x0, [x1]
cbz x0, slave_cpu
br x0 /* branch to the given address */
-master_cpu:
- /* On the master CPU */
#endif /* CONFIG_ARMV8_MULTIENTRY */
-
+master_cpu:
bl _main
#ifdef CONFIG_SYS_RESET_SCTRL