Re: [PATCH v4 2/5] RISC-V: Add SBI debug console helper routines

Andrew Jones
2023-11-20T08:05:34Z

On Sat, Nov 18, 2023 at 09:08:56AM +0530, Anup Patel wrote:
> Let us provide SBI debug console helper routines which can be
> shared by serial/earlycon-riscv-sbi.c and hvc/hvc_riscv_sbi.c.
>
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> ---
> arch/riscv/include/asm/sbi.h | 5 +++++
> arch/riscv/kernel/sbi.c | 43 ++++++++++++++++++++++++++++++++++++
> 2 files changed, 48 insertions(+)
>
> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> index 66f3933c14f6..ee7aef5f6233 100644
> --- a/arch/riscv/include/asm/sbi.h
> +++ b/arch/riscv/include/asm/sbi.h
> @@ -334,6 +334,11 @@ static inline unsigned long sbi_mk_version(unsigned long major,
> }
>
> int sbi_err_map_linux_errno(int err);
> +
> +extern bool sbi_debug_console_available;
> +int sbi_debug_console_write(unsigned int num_bytes, phys_addr_t base_addr);
> +int sbi_debug_console_read(unsigned int num_bytes, phys_addr_t base_addr);
> +
> #else /* CONFIG_RISCV_SBI */
> static inline int sbi_remote_fence_i(const struct cpumask *cpu_mask) { return -1; }
> static inline void sbi_init(void) {}
> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> index 5a62ed1da453..73a9c22c3945 100644
> --- a/arch/riscv/kernel/sbi.c
> +++ b/arch/riscv/kernel/sbi.c
> @@ -571,6 +571,44 @@ long sbi_get_mimpid(void)
> }
> EXPORT_SYMBOL_GPL(sbi_get_mimpid);
>
> +bool sbi_debug_console_available;
> +
> +int sbi_debug_console_write(unsigned int num_bytes, phys_addr_t base_addr)
> +{
> + struct sbiret ret;
> +
> + if (!sbi_debug_console_available)
> + return -EOPNOTSUPP;
> +
> + if (IS_ENABLED(CONFIG_32BIT))
> + ret = sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_WRITE,
> + num_bytes, lower_32_bits(base_addr),
> + upper_32_bits(base_addr), 0, 0, 0);
> + else
> + ret = sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_WRITE,
> + num_bytes, base_addr, 0, 0, 0, 0);
> +
> + return ret.error ? sbi_err_map_linux_errno(ret.error) : ret.value;

We can't get perfect mappings, but I wonder if we can do better than
returning ENOTSUPP for "Failed to write the byte due to I/O errors."

How about

if (ret.error == SBI_ERR_FAILURE)
return -EIO;

return ret.error ? sbi_err_map_linux_errno(ret.error) : ret.value;

> +}
> +
> +int sbi_debug_console_read(unsigned int num_bytes, phys_addr_t base_addr)
> +{
> + struct sbiret ret;
> +
> + if (!sbi_debug_console_available)
> + return -EOPNOTSUPP;
> +
> + if (IS_ENABLED(CONFIG_32BIT))
> + ret = sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_READ,
> + num_bytes, lower_32_bits(base_addr),
> + upper_32_bits(base_addr), 0, 0, 0);
> + else
> + ret = sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_READ,
> + num_bytes, base_addr, 0, 0, 0, 0);
> +
> + return ret.error ? sbi_err_map_linux_errno(ret.error) : ret.value;

Same comment as above.

> +}
> +
> void __init sbi_init(void)
> {
> int ret;
> @@ -612,6 +650,11 @@ void __init sbi_init(void)
> sbi_srst_reboot_nb.priority = 192;
> register_restart_handler(&sbi_srst_reboot_nb);
> }
> + if ((sbi_spec_version >= sbi_mk_version(2, 0)) &&
> + (sbi_probe_extension(SBI_EXT_DBCN) > 0)) {
> + pr_info("SBI DBCN extension detected\n");
> + sbi_debug_console_available = true;
> + }
> } else {
> __sbi_set_timer = __sbi_set_timer_v01;
> __sbi_send_ipi = __sbi_send_ipi_v01;
> --
> 2.34.1
>

Otherwise,

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

Thanks,
drew