armv8: spl: Support separate stack for TPL

To allow a TPL and SPL to run from different addresses/memories, we
need to split setup of the TPL and SPL stacks.  To do so, we introduce
CONFIG_TPL_STACK (not listed in Kconfig) which can be used to override
the initial stack pointer for TPL.

To provide backward compatibility for existing boards, this is added
as an optional configuration item and the normal search order (i.e.
SPL_STACK, then SYS_STACK) apply if not defined.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

arch/arm/lib/crt0_64.S

@@ -69,7 +69,9 @@ ENTRY(_main)
 /*
  * Set up initial C runtime environment and call board_init_f(0).
  */
-#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
+#if defined(CONFIG_TPL_BUILD) && defined(CONFIG_TPL_STACK)
+	ldr	x0, =(CONFIG_TPL_STACK)
+#elif defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
 	ldr	x0, =(CONFIG_SPL_STACK)
 #else
 	ldr	x0, =(CONFIG_SYS_INIT_SP_ADDR)

scripts/config_whitelist.txt

@@ -4911,6 +4911,7 @@ CONFIG_TI_SPI_MMAP
 CONFIG_TMU_TIMER
 CONFIG_TPL_DRIVERS_MISC_SUPPORT
 CONFIG_TPL_PAD_TO
+CONFIG_TPL_STACK
 CONFIG_TPM_TIS_BASE_ADDRESS
 CONFIG_TPS6586X_POWER
 CONFIG_TQM834X