[PATCH v5 5/8] lib: sbi: Implement SBI debug console extension

[Andrew Jones <ajones@ventanamicro.com>]

On Fri, Jan 13, 2023 at 05:11:07PM +0530, Anup Patel wrote:
> We implement SBI debug console extension as one of the replacement
> SBI extensions. This extension is only available when OpenSBI platform
> provides a console device to generic library.
> 
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> Reviewed-by: Atish Patra <atishp@rivosinc.com>
> Reviewed-by: Xiang W <wxjstz@126.com>
> Reviewed-by: Bin Meng <bmeng@tinylab.org>
> ---
>  lib/sbi/Kconfig          |  4 +++
>  lib/sbi/objects.mk       |  3 ++
>  lib/sbi/sbi_ecall_dbcn.c | 72 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 79 insertions(+)
>  create mode 100644 lib/sbi/sbi_ecall_dbcn.c
> 
> diff --git a/lib/sbi/Kconfig b/lib/sbi/Kconfig
> index df74bba..ef6728b 100644
> --- a/lib/sbi/Kconfig
> +++ b/lib/sbi/Kconfig
> @@ -26,6 +26,10 @@ config SBI_ECALL_PMU
>  	bool "Performance Monitoring Unit extension"
>  	default y
>  
> +config SBI_ECALL_DBCN
> +	bool "Debug Console extension"
> +	default y
> +
>  config SBI_ECALL_LEGACY
>  	bool "SBI v0.1 legacy extensions"
>  	default y
> diff --git a/lib/sbi/objects.mk b/lib/sbi/objects.mk
> index c774ebb..319f38d 100644
> --- a/lib/sbi/objects.mk
> +++ b/lib/sbi/objects.mk
> @@ -37,6 +37,9 @@ libsbi-objs-$(CONFIG_SBI_ECALL_SRST) += sbi_ecall_srst.o
>  carray-sbi_ecall_exts-$(CONFIG_SBI_ECALL_PMU) += ecall_pmu
>  libsbi-objs-$(CONFIG_SBI_ECALL_PMU) += sbi_ecall_pmu.o
>  
> +carray-sbi_ecall_exts-$(CONFIG_SBI_ECALL_DBCN) += ecall_dbcn
> +libsbi-objs-$(CONFIG_SBI_ECALL_DBCN) += sbi_ecall_dbcn.o
> +
>  carray-sbi_ecall_exts-$(CONFIG_SBI_ECALL_LEGACY) += ecall_legacy
>  libsbi-objs-$(CONFIG_SBI_ECALL_LEGACY) += sbi_ecall_legacy.o
>  
> diff --git a/lib/sbi/sbi_ecall_dbcn.c b/lib/sbi/sbi_ecall_dbcn.c
> new file mode 100644
> index 0000000..bfa40e9
> --- /dev/null
> +++ b/lib/sbi/sbi_ecall_dbcn.c
> @@ -0,0 +1,72 @@
> +/*
> + * SPDX-License-Identifier: BSD-2-Clause
> + *
> + * Copyright (c) 2022 Ventana Micro Systems Inc.
> + *
> + * Authors:
> + *   Anup Patel <apatel@ventanamicro.com>
> + */
> +
> +#include <sbi/sbi_console.h>
> +#include <sbi/sbi_domain.h>
> +#include <sbi/sbi_error.h>
> +#include <sbi/sbi_ecall.h>
> +#include <sbi/sbi_ecall_interface.h>
> +#include <sbi/sbi_trap.h>
> +#include <sbi/riscv_asm.h>
> +
> +static int sbi_ecall_dbcn_handler(unsigned long extid, unsigned long funcid,
> +				  const struct sbi_trap_regs *regs,
> +				  unsigned long *out_val,
> +				  struct sbi_trap_info *out_trap)
> +{
> +	ulong smode = (csr_read(CSR_MSTATUS) & MSTATUS_MPP) >>
> +			MSTATUS_MPP_SHIFT;
> +
> +	switch (funcid) {
> +	case SBI_EXT_DBCN_CONSOLE_WRITE:
> +	case SBI_EXT_DBCN_CONSOLE_READ:
> +		/*
> +		 * On RV32, the M-mode can only access the first 4GB of
> +		 * the physical address space because M-mode does not have
> +		 * MMU to access full 34-bit physical address space.
> +		 *
> +		 * Based on above, we simply fail if the upper 32bits of
> +		 * the physical address (i.e. a2 register) is non-zero on
> +		 * RV32.
> +		 */
> +#if __riscv_xlen == 32
> +		if (regs->a2)
> +			return SBI_ERR_FAILED;

The spec drafts says SBI_ERR_FAILED is only for I/O errors. I think
we should extend the spec draft to point this situation out and return
SBI_ERR_INVALID_ADDRESS.

> +#endif
> +		if (!sbi_domain_check_addr_range(sbi_domain_thishart_ptr(),
> +					regs->a1, regs->a0, smode,
> +					SBI_DOMAIN_READ|SBI_DOMAIN_WRITE))
> +			return SBI_EINVALID_ADDR;

The spec draft says this should be SBI_ERR_INVALID_PARAM

> +		if (funcid == SBI_EXT_DBCN_CONSOLE_WRITE)
> +			sbi_nputs((const char *)regs->a1, regs->a0);
> +		else
> +			*out_val = sbi_ngets((char *)regs->a1, regs->a0);
> +		return 0;
> +	case SBI_EXT_DBCN_CONSOLE_WRITE_BYTE:
> +		sbi_putc(regs->a0);
> +		return 0;
> +	default:
> +		break;
> +	}
> +
> +	return SBI_ENOTSUPP;
> +}
> +
> +static int sbi_ecall_dbcn_probe(unsigned long extid, unsigned long *out_val)
> +{
> +	*out_val = (sbi_console_get_device()) ? 1 : 0;

nit: Unnecessary ()

> +	return 0;
> +}
> +
> +struct sbi_ecall_extension ecall_dbcn = {
> +	.extid_start = SBI_EXT_DBCN,
> +	.extid_end = SBI_EXT_DBCN,
> +	.handle = sbi_ecall_dbcn_handler,
> +	.probe = sbi_ecall_dbcn_probe,
> +};
> -- 
> 2.34.1
> 
>

Thanks,
drew