riscv: ae250: Support DT provided by the board at runtime
Enable CONFIG_OF_BOAD to support delivery dtb to u-boot
at run time instead of embedded.
There are two methods to delivery dtb.
1 Pass from loader:
When u-boot boot from RAM, gdb or loader can pass dtb
via a2 to u-boot dynamically. Of course gdb or loader
shall be in charge of dtb delivery.
2 Configure CONFIG_SYS_FDT_BASE:
It can be configured as RAM or ROM base statically,
no mater u-boot boot from RAM or ROM.
If it was configured as ROM base, dtb can be burned
into ROM(spi flash) by spi driver.
Meanwhile remove CONFIG_SKIP_LOWLEVEL_INIT which is
useless in nx25-ae250 configuration.
Signed-off-by: Rick Chen <rick@andestech.com>
Signed-off-by: Rick Chen <rickchen36@gmail.com>
Cc: Greentime Hu <green.hu@gmail.com>
diff --git a/arch/riscv/cpu/nx25/start.S b/arch/riscv/cpu/nx25/start.S
index 6a07663..cd0a663 100644
--- a/arch/riscv/cpu/nx25/start.S
+++ b/arch/riscv/cpu/nx25/start.S
@@ -45,6 +45,8 @@
.global trap_entry
handle_reset:
+ li t0, CONFIG_SYS_SDRAM_BASE
+ SREG a2, 0(t0)
la t0, trap_entry
csrw mtvec, t0
csrwi mstatus, 0