linux-kernel - Re: [PATCH] tty: hvc: Don't enable the RISC-V SBI console by default

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Date: Wed, 14 Feb 2024 21:20:13 +0530
From: Anup Patel <anup@...infault.org>
To: Palmer Dabbelt <palmer@...osinc.com>
Cc: linux-riscv@...ts.infradead.org, Greg KH <gregkh@...uxfoundation.org>, 
	jirislaby@...nel.org, Atish Patra <atishp@...osinc.com>, ajones@...tanamicro.com, 
	apatel@...tanamicro.com, linuxppc-dev@...ts.ozlabs.org, 
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org, 
	Emil Renner Berthing <kernel@...il.dk>
Subject: Re: [PATCH] tty: hvc: Don't enable the RISC-V SBI console by default

On Wed, Feb 14, 2024 at 9:06 PM Palmer Dabbelt <palmer@...osinc.com> wrote:
>
> From: Palmer Dabbelt <palmer@...osinc.com>
>
> The new SBI console has the same problem as the old one: there's only
> one shared backing hardware and no synchronization, so the two drivers
> end up stepping on each other.  This was the same issue the old SBI-0.1
> console drivers had, but that was disabled by default when SBI-0.1 was.
>
> So just mark the new driver as nonportable.
>
> Reported-by: Emil Renner Berthing <kernel@...il.dk>
> Fixes: 88ead68e764c ("tty: Add SBI debug console support to HVC SBI driver")
> Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>

LTGM.

Reviewed-by: Anup Patel <anup@...infault.org>

Regards,
Anup

> ---
>  drivers/tty/hvc/Kconfig | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/tty/hvc/Kconfig b/drivers/tty/hvc/Kconfig
> index 6e05c5c7bca1..c2a4e88b328f 100644
> --- a/drivers/tty/hvc/Kconfig
> +++ b/drivers/tty/hvc/Kconfig
> @@ -108,13 +108,15 @@ config HVC_DCC_SERIALIZE_SMP
>
>  config HVC_RISCV_SBI
>         bool "RISC-V SBI console support"
> -       depends on RISCV_SBI
> +       depends on RISCV_SBI && NONPORTABLE
>         select HVC_DRIVER
>         help
>           This enables support for console output via RISC-V SBI calls, which
> -         is normally used only during boot to output printk.
> +         is normally used only during boot to output printk.  This driver
> +         conflicts with real console drivers and should not be enabled on
> +         systems that directly access the console.
>
> -         If you don't know what do to here, say Y.
> +         If you don't know what do to here, say N.
>
>  config HVCS
>         tristate "IBM Hypervisor Virtual Console Server support"
> --
> 2.43.0
>
>