[PATCH 4/7] riscv: dts: introduce SPL_LOAD_FIT_OPENSBI_OS_BOOT symbol

[Randolph]

Introduce common Kconfig symbol for riscv architecture.
This symbol SPL_LOAD_FIT_OPENSBI_OS_BOOT is like falcon mode on ARM,
the Falcon boot is a shortcut boot method for SD/eMMC targets. It
skips the loading the RAM version U-Boot. Instead, it will loads
the FIT image and boots directly to Linux.

When SPL_OPENSBI_OS_BOOT is enabled, linux.itb is created after
compilation instead of the default u-boot.itb. It initialises memory
with the U-Boot SPL at the first stage, just as a normal boot process
does at the beginning. Instead of jumping to the U-Boot proper from
OpenSBI before booting the Linux kernel, the RISC-V falcon mode
process jumps directly to the Linux kernel to gain shorter booting time.

When SPL_OPENSBI_OS_BOOT is enabled, it will change the default FIT
configure file "binman.dtsi" to "binman_linux.dtsi"
Default is not enabled.

Signed-off-by: Randolph <randolph at andestech.com>
---
 arch/riscv/Kconfig | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index ec1cfcaaa7..4f104789a7 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -422,8 +422,17 @@ config TPL_USE_ARCH_MEMSET
 
 endmenu
 
+config SPL_LOAD_FIT_OPENSBI_OS_BOOT
+	bool "Enable SPL (OpenSBI OS boot mode) applying linux from FIT"
+	depends on SPL_LOAD_FIT
+	help
+	  Use fw_dynamic from the FIT image, and u-boot SPL will invoke it directly.
+	  This is a shortcut boot flow, from u-boot SPL -> OpenSBI -> u-boot proper
+	  -> linux to u-boot SPL -> OpenSBI -> linux.
+
 config SPL_LOAD_FIT_CONFIG
 	string "Default FIT configuration for SPL"
+	default "binman_linux.dtsi" if SPL_LOAD_FIT_OPENSBI_OS_BOOT
 	default "binman.dtsi"
 	depends on SPL_LOAD_FIT
 	help
-- 
2.34.1