Hi Sean, On Thu, Sep 22, 2022 at 10:35 PM Sean Anderson <sean.ander...@seco.com> wrote: > > > > On 9/19/22 7:49 AM, Kautuk Consul wrote: > > 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-spec.adoc > > > > Signed-off-by: Anup Patel <apa...@ventanamicro.com> > > Signed-off-by: Kautuk Consul <kcon...@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 | 6 +++--- > > 5 files changed, 41 insertions(+), 3 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)) { > > Hm, shouldn't we check to see if this is actually a semihosting > breakpoint? This involves reading the prior and posterior > instructions, which might be a bit too much. Alternatively, we > could only take this trap if semihosting_enabled(), which would > limit any suppression of spurious breakpoints to one instruction. >
Agreed. Will read the prior and posterior instructions in v5 and send this out. Thanks. > > + /* 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..eed3a231d9 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 > > @@ -108,8 +108,8 @@ 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 > > + depends on SPL_SEMIHOSTING && (ARM64 || RISCV) > > + select ARMV8_SPL_EXCEPTION_VECTORS if ARM64 > > default y > > help > > Normally, if U-Boot makes a semihosting call and no debugger is > > > > The rest looks fine. > > --Sean