We add RISC-V semihosting based serial console for JTAG based early debugging.
The RISC-V semihosting specification is available at: https://github.com/riscv/riscv-semihosting-spec/blob/main/riscv-semihosting-...
Signed-off-by: Anup Patel apatel@ventanamicro.com Signed-off-by: Kautuk Consul kconsul@ventanamicro.com --- arch/riscv/include/asm/spl.h | 1 + arch/riscv/lib/Makefile | 2 ++ arch/riscv/lib/interrupts.c | 11 +++++++++++ arch/riscv/lib/semihosting.c | 24 ++++++++++++++++++++++++ lib/Kconfig | 4 ++-- 5 files changed, 40 insertions(+), 2 deletions(-) create mode 100644 arch/riscv/lib/semihosting.c
diff --git a/arch/riscv/include/asm/spl.h b/arch/riscv/include/asm/spl.h index e8a94fcb1f..2898a770ee 100644 --- a/arch/riscv/include/asm/spl.h +++ b/arch/riscv/include/asm/spl.h @@ -25,6 +25,7 @@ enum { BOOT_DEVICE_DFU, BOOT_DEVICE_XIP, BOOT_DEVICE_BOOTROM, + BOOT_DEVICE_SMH, BOOT_DEVICE_NONE };
diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile index 06020fcc2a..64e29804c1 100644 --- a/arch/riscv/lib/Makefile +++ b/arch/riscv/lib/Makefile @@ -42,3 +42,5 @@ extra-$(CONFIG_EFI) += $(EFI_CRT0) $(EFI_RELOC) obj-$(CONFIG_$(SPL_TPL_)USE_ARCH_MEMSET) += memset.o obj-$(CONFIG_$(SPL_TPL_)USE_ARCH_MEMMOVE) += memmove.o obj-$(CONFIG_$(SPL_TPL_)USE_ARCH_MEMCPY) += memcpy.o + +obj-$(CONFIG_$(SPL_TPL_)SEMIHOSTING) += semihosting.o diff --git a/arch/riscv/lib/interrupts.c b/arch/riscv/lib/interrupts.c index 100be2e966..bd7cd772b8 100644 --- a/arch/riscv/lib/interrupts.c +++ b/arch/riscv/lib/interrupts.c @@ -17,6 +17,7 @@ #include <asm/ptrace.h> #include <asm/system.h> #include <asm/encoding.h> +#include <semihosting.h>
DECLARE_GLOBAL_DATA_PTR;
@@ -149,6 +150,16 @@ ulong handle_trap(ulong cause, ulong epc, ulong tval, struct pt_regs *regs) /* An UEFI application may have changed gd. Restore U-Boot's gd. */ efi_restore_gd();
+ if (cause == CAUSE_BREAKPOINT && + CONFIG_IS_ENABLED(SEMIHOSTING_FALLBACK)) { + /* For semihosting fallback we simply skip the ebreak + * instruction. + */ + disable_semihosting(); + epc += 4; + return epc; + } + is_irq = (cause & MCAUSE_INT); irq = (cause & ~MCAUSE_INT);
diff --git a/arch/riscv/lib/semihosting.c b/arch/riscv/lib/semihosting.c new file mode 100644 index 0000000000..d6593b02a6 --- /dev/null +++ b/arch/riscv/lib/semihosting.c @@ -0,0 +1,24 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (C) 2022 Ventana Micro Systems Inc. + */ + +#include <common.h> + +long smh_trap(int sysnum, void *addr) +{ + register int ret asm ("a0") = sysnum; + register void *param0 asm ("a1") = addr; + + asm volatile (".align 4\n" + ".option push\n" + ".option norvc\n" + + "slli zero, zero, 0x1f\n" + "ebreak\n" + "srai zero, zero, 7\n" + ".option pop\n" + : "+r" (ret) : "r" (param0) : "memory"); + + return ret; +} diff --git a/lib/Kconfig b/lib/Kconfig index 97920e7552..d1f5262b20 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -85,7 +85,7 @@ config SEMIHOSTING
config SEMIHOSTING_FALLBACK bool "Recover gracefully when semihosting fails" - depends on SEMIHOSTING && ARM64 + depends on SEMIHOSTING && (ARM64 || RISCV) default y help Normally, if U-Boot makes a semihosting call and no debugger is @@ -109,7 +109,7 @@ config SPL_SEMIHOSTING config SPL_SEMIHOSTING_FALLBACK bool "Recover gracefully when semihosting fails in SPL" depends on SPL_SEMIHOSTING && ARM64 - select ARMV8_SPL_EXCEPTION_VECTORS + select ARMV8_SPL_EXCEPTION_VECTORS if ARM64 default y help Normally, if U-Boot makes a semihosting call and no debugger is