Re: [PATCH v2 6/8] tty/serial: Add RISC-V SBI debug console based earlycon

[Andrew Jones]

On Thu, Oct 12, 2023 at 10:45:07AM +0530, Anup Patel wrote:
> We extend the existing RISC-V SBI earlycon support to use the new
> RISC-V SBI debug console extension.
> 
> Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> ---
>  drivers/tty/serial/Kconfig              |  2 +-
>  drivers/tty/serial/earlycon-riscv-sbi.c | 32 +++++++++++++++++++++----
>  2 files changed, 29 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index bdc568a4ab66..cec46091a716 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -87,7 +87,7 @@ config SERIAL_EARLYCON_SEMIHOST
>  
>  config SERIAL_EARLYCON_RISCV_SBI
>  	bool "Early console using RISC-V SBI"
> -	depends on RISCV_SBI_V01
> +	depends on RISCV_SBI
>  	select SERIAL_CORE
>  	select SERIAL_CORE_CONSOLE
>  	select SERIAL_EARLYCON
> diff --git a/drivers/tty/serial/earlycon-riscv-sbi.c b/drivers/tty/serial/earlycon-riscv-sbi.c
> index 27afb0b74ea7..c21cdef254e7 100644
> --- a/drivers/tty/serial/earlycon-riscv-sbi.c
> +++ b/drivers/tty/serial/earlycon-riscv-sbi.c
> @@ -15,17 +15,41 @@ static void sbi_putc(struct uart_port *port, unsigned char c)
>  	sbi_console_putchar(c);
>  }
>  
> -static void sbi_console_write(struct console *con,
> -			      const char *s, unsigned n)
> +static void sbi_0_1_console_write(struct console *con,
> +				  const char *s, unsigned int n)
>  {
>  	struct earlycon_device *dev = con->data;
>  	uart_console_write(&dev->port, s, n, sbi_putc);
>  }
>  
> +static void sbi_dbcn_console_write(struct console *con,
> +				   const char *s, unsigned int n)
> +{
> +	phys_addr_t pa = __pa(s);
> +
> +	if (IS_ENABLED(CONFIG_32BIT))
> +		sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_WRITE,
> +			  n, lower_32_bits(pa), upper_32_bits(pa), 0, 0, 0);
> +	else
> +		sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_WRITE,
> +			  n, pa, 0, 0, 0, 0);
> +}
> +
>  static int __init early_sbi_setup(struct earlycon_device *device,
>  				  const char *opt)
>  {
> -	device->con->write = sbi_console_write;
> -	return 0;
> +	int ret = 0;
> +
> +	if ((sbi_spec_version >= sbi_mk_version(2, 0)) &&
> +	    (sbi_probe_extension(SBI_EXT_DBCN) > 0)) {
> +		device->con->write = sbi_dbcn_console_write;
> +	} else {
> +		if (IS_ENABLED(CONFIG_RISCV_SBI_V01))
> +			device->con->write = sbi_0_1_console_write;
> +		else
> +			ret = -ENODEV;
> +	}
> +
> +	return ret;
>  }
>  EARLYCON_DECLARE(sbi, early_sbi_setup);
> -- 
> 2.34.1
>

Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>