Hi Lukas

rick@andestech.com 於 2019年3月12日 週二 下午7:04寫道：

...

-----Original Message----- From: Lukas Auer [mailto:lukas.auer@aisec.fraunhofer.de] Sent: Wednesday, March 06, 2019 6:53 AM To: u-boot@lists.denx.de Cc: Atish Patra; Anup Patel; Bin Meng; Andreas Schwab; Palmer Dabbelt; Alexander Graf; Lukas Auer; Rick Jian-Zhi Chen(陳建志); Anup Patel Subject: [PATCH v2 7/9] riscv: do not rely on hart ID passed by previous boot stage

RISC-V U-Boot expects the hart ID to be passed to it via register a0 by the previous boot stage. Machine mode firmware such as BBL and OpenSBI do this when starting their payload (U-Boot) in supervisor mode. If U-Boot is running in machine mode, this task must be handled by the boot ROM. Explicitly populate register a0 with the hart ID from the mhartid CSR to avoid possible problems on RISC-V processors with a boot ROM that does not handle this task.

Suggested-by: Rick Chen rick@andestech.com Signed-off-by: Lukas Auer lukas.auer@aisec.fraunhofer.de

---

Changes in v2:

• New patch to populate register a0 with the hart ID from the mhartid CSR in

machine-mode

arch/riscv/cpu/start.S | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S index 79b753847c..d4daa6e0bf 100644 --- a/arch/riscv/cpu/start.S +++ b/arch/riscv/cpu/start.S @@ -36,6 +36,10 @@ .section .text .globl _start _start: +#ifdef CONFIG_RISCV_MMODE

• csrr    a0, mhartid
  

+#endif

• /* save hart id and dtb pointer */
  mv      s0, a0
  mv      s1, a1
  

Reviewed-by: Rick Chen rick@andestech.com Tested-by: Rick Chen rick@andestech.com

Thanks Rick