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

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Message-ID: <adf2a8f4-f675-4d27-8b46-5d80d3251b6c@sifive.com>
Date:   Tue, 21 Nov 2023 16:45:51 -0600
From:   Samuel Holland <samuel.holland@...ive.com>
To:     Anup Patel <apatel@...tanamicro.com>
Cc:     Conor Dooley <conor@...nel.org>,
        Andrew Jones <ajones@...tanamicro.com>,
        linux-riscv@...ts.infradead.org, linux-serial@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>
Subject: Re: [PATCH v4 2/5] RISC-V: Add SBI debug console helper routines

Hi Anup,

On 2023-11-17 9:38 PM, 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@...tanamicro.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;
> +}
> +
> +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;
> +}

Since every place that calls these functions will need to do the vmalloc lookup,
would it make sense to do it here, and have these take a pointer instead?

Regards,
Samuel