From d2db2a8fa4f190d6d78ee7e9e642a180664cbccf Mon Sep 17 00:00:00 2001 From: Anup Patel Date: Mon, 3 Dec 2018 10:57:40 +0530 Subject: [PATCH] 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 CSRs instead of m 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 Reviewed-by: Bin Meng Tested-by: Bin Meng Reviewed-by: Lukas Auer --- arch/riscv/Kconfig | 5 +++++ arch/riscv/cpu/start.S | 23 +++++++++++++++-------- arch/riscv/include/asm/encoding.h | 6 ++++++ arch/riscv/lib/interrupts.c | 31 ++++++++++++++++++++++--------- 4 files changed, 48 insertions(+), 17 deletions(-) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 3e0af55e71..732a357a99 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -55,6 +55,11 @@ config RISCV_ISA_C config RISCV_ISA_A def_bool y +config RISCV_SMODE + bool "Run in S-Mode" + help + Enable this option to build U-Boot for RISC-V S-Mode + config 32BIT bool 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) diff --git a/arch/riscv/include/asm/encoding.h b/arch/riscv/include/asm/encoding.h index 9ea50ce640..97cf906aa6 100644 --- a/arch/riscv/include/asm/encoding.h +++ b/arch/riscv/include/asm/encoding.h @@ -7,6 +7,12 @@ #ifndef RISCV_CSR_ENCODING_H #define RISCV_CSR_ENCODING_H +#ifdef CONFIG_RISCV_SMODE +#define MODE_PREFIX(__suffix) s##__suffix +#else +#define MODE_PREFIX(__suffix) m##__suffix +#endif + #define MSTATUS_UIE 0x00000001 #define MSTATUS_SIE 0x00000002 #define MSTATUS_HIE 0x00000004 diff --git a/arch/riscv/lib/interrupts.c b/arch/riscv/lib/interrupts.c index 903a1c4cd5..3aff006977 100644 --- a/arch/riscv/lib/interrupts.c +++ b/arch/riscv/lib/interrupts.c @@ -34,17 +34,30 @@ int disable_interrupts(void) return 0; } -ulong handle_trap(ulong mcause, ulong epc, struct pt_regs *regs) +ulong handle_trap(ulong cause, ulong epc, struct pt_regs *regs) { - ulong is_int; + ulong is_irq, irq; - is_int = (mcause & MCAUSE_INT); - if ((is_int) && ((mcause & MCAUSE_CAUSE) == IRQ_M_EXT)) - external_interrupt(0); /* handle_m_ext_interrupt */ - else if ((is_int) && ((mcause & MCAUSE_CAUSE) == IRQ_M_TIMER)) - timer_interrupt(0); /* handle_m_timer_interrupt */ - else - _exit_trap(mcause, epc, regs); + is_irq = (cause & MCAUSE_INT); + irq = (cause & ~MCAUSE_INT); + + if (is_irq) { + switch (irq) { + case IRQ_M_EXT: + case IRQ_S_EXT: + external_interrupt(0); /* handle external interrupt */ + break; + case IRQ_M_TIMER: + case IRQ_S_TIMER: + timer_interrupt(0); /* handle timer interrupt */ + break; + default: + _exit_trap(cause, epc, regs); + break; + }; + } else { + _exit_trap(cause, epc, regs); + } return epc; } -- 2.39.5