This patchset allows us runing u-boot in S-mode which is useful on platforms where M-mode runtime firmware is an independent firmware and u-boot is used as last stage OS bootloader.
The patchset based upon git://git.denx.de/u-boot-riscv.git and is tested on QEMU in both M-mode and S-mode.
For S-mode testing, we have used u-boot.bin as payload of latest BBL (at commit 6ebd0f2a46255d0c76dad3c05b16c1d154795d26) applied with following changes:
diff --git a/machine/emulation.c b/machine/emulation.c index 132e977..def75e1 100644 --- a/machine/emulation.c +++ b/machine/emulation.c @@ -162,6 +162,12 @@ static inline int emulate_read_csr(int num, uintptr_t mstatus, uintptr_t* result
switch (num) { + case CSR_MISA: + *result = read_csr(misa); + return 0; + case CSR_MHARTID: + *result = read_csr(mhartid); + return 0; case CSR_CYCLE: if (!((counteren >> (CSR_CYCLE - CSR_CYCLE)) & 1)) return -1;
Changes since v1: - Rebased upon latest git://git.denx.de/u-boot-riscv.git - Add details in cover letter for running u-boot in S-mode using BBL
Anup Patel (3): riscv: Add kconfig option to run u-boot in S-mode riscv: qemu: Use different SYS_TEXT_BASE for S-mode riscv: Add S-mode defconfigs for QEMU virt machine
arch/riscv/Kconfig | 6 +++++ arch/riscv/cpu/start.S | 33 ++++++++++++++++++++++++++++ board/emulation/qemu-riscv/Kconfig | 3 ++- configs/qemu-riscv32-smode_defconfig | 10 +++++++++ configs/qemu-riscv64-smode_defconfig | 11 ++++++++++ 5 files changed, 62 insertions(+), 1 deletion(-) create mode 100644 configs/qemu-riscv32-smode_defconfig create mode 100644 configs/qemu-riscv64-smode_defconfig