Am 9. August 2020 18:35:45 MESZ schrieb Sean Anderson seanga2@gmail.com:
On 8/9/20 12:14 PM, Heinrich Schuchardt wrote:
Hello Sean,
while trying to understand the handling of SMP I stumbled of this
question:
Why did you define CONFIG_SYS_INIT_SP_ADDR as an odd number on the
MAIX
in commit a7c81fc85326 ("riscv: Add Sipeed Maix support") while the other RISC-V boards use an even number:
include/configs/sifive-fu540.h:29: 29 | #define CONFIG_SYS_INIT_SP_ADDR (CONFIG_SYS_SDRAM_BASE +
SZ_2M)
include/configs/qemu-riscv.h:22: 22 | #define CONFIG_SYS_INIT_SP_ADDR (CONFIG_SYS_SDRAM_BASE +
SZ_2M)
include/configs/sipeed-maix.h:13: 13 | #define CONFIG_SYS_INIT_SP_ADDR 0x803FFFFF
I always thought that RISC-V stack pointers must be 16 byte aligned:
Cf. https://riscv.org/wp-content/uploads/2015/01/riscv-calling.pdf
"In the standard RISC-V calling convention, the stack grows downward
and
the stack pointer is always kept 16-byte aligned."
Because that is the top of (non-ai) ram. And it gets 16-byte aligned by call_board_init_f anyway.
--Sean
Top of RAM is the place to which we want to relocate U-Boot. But furthermore this value minus a multiple of16KiB is also used for the stack lication of the secondary CPU.
Shouldn't we better use the same definition as the other boards?