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| author | Anup Patel <anup@brainfault.org> | 2018-12-03 10:57:40 +0530 |
|---|---|---|
| committer | Andes <uboot@andestech.com> | 2018-12-05 14:13:53 +0800 |
| commit | d2db2a8fa4f190d6d78ee7e9e642a180664cbccf (patch) | |
| tree | 065e64b9073f659188b32040bdaeba90dc33776b /arch/riscv/cpu/start.S | |
| parent | 2e2a2a5d4f0c2e2642326d9000ce1f1553632e6a (diff) | |
| download | u-boot-d2db2a8fa4f190d6d78ee7e9e642a180664cbccf.tar.gz u-boot-d2db2a8fa4f190d6d78ee7e9e642a180664cbccf.tar.xz u-boot-d2db2a8fa4f190d6d78ee7e9e642a180664cbccf.zip | |
riscv: Add kconfig option to run U-Boot in S-mode
This patch adds kconfig option RISCV_SMODE to run U-Boot in
S-mode. When this opition is enabled we use s<xyz> CSRs instead
of m<xyz> CSRs.
It is important to note that there is no equivalent S-mode CSR
for misa and mhartid CSRs so we expect M-mode runtime firmware
(BBL or equivalent) to emulate misa and mhartid CSR read.
In-future, we will have more patches to avoid accessing misa and
mhartid CSRs from S-mode.
Signed-off-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Diffstat (limited to 'arch/riscv/cpu/start.S')
| -rw-r--r-- | arch/riscv/cpu/start.S | 23 |
1 files changed, 15 insertions, 8 deletions
diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S index 15e1b8199a..3f055bdb7e 100644 --- a/arch/riscv/cpu/start.S +++ b/arch/riscv/cpu/start.S @@ -41,10 +41,10 @@ _start: li t0, CONFIG_SYS_SDRAM_BASE SREG a2, 0(t0) la t0, trap_entry - csrw mtvec, t0 + csrw MODE_PREFIX(tvec), t0 /* mask all interrupts */ - csrw mie, zero + csrw MODE_PREFIX(ie), zero /* Enable cache */ jal icache_enable @@ -166,7 +166,7 @@ fix_rela_dyn: */ la t0, trap_entry add t0, t0, t6 - csrw mtvec, t0 + csrw MODE_PREFIX(tvec), t0 clear_bss: la t0, __bss_start /* t0 <- rel __bss_start in FLASH */ @@ -238,17 +238,24 @@ trap_entry: SREG x29, 29*REGBYTES(sp) SREG x30, 30*REGBYTES(sp) SREG x31, 31*REGBYTES(sp) - csrr a0, mcause - csrr a1, mepc + csrr a0, MODE_PREFIX(cause) + csrr a1, MODE_PREFIX(epc) mv a2, sp jal handle_trap - csrw mepc, a0 + csrw MODE_PREFIX(epc), a0 +#ifdef CONFIG_RISCV_SMODE +/* + * Remain in S-mode after sret + */ + li t0, SSTATUS_SPP +#else /* * Remain in M-mode after mret */ li t0, MSTATUS_MPP - csrs mstatus, t0 +#endif + csrs MODE_PREFIX(status), t0 LREG x1, 1*REGBYTES(sp) LREG x2, 2*REGBYTES(sp) LREG x3, 3*REGBYTES(sp) @@ -281,4 +288,4 @@ trap_entry: LREG x30, 30*REGBYTES(sp) LREG x31, 31*REGBYTES(sp) addi sp, sp, 32*REGBYTES - mret + MODE_PREFIX(ret) |