Re: [PATCH] tty: Don't force RISCV SBI console as preferred console

[Atish Patra]

On 4/25/19 6:35 AM, Anup Patel wrote:
> The Linux kernel will auto-disables all boot consoles whenever it
> gets a preferred real console.
>
> Currently on RISC-V systems, if we have a real console which is not
> RISCV SBI console then boot consoles (such as earlycon=sbi) are not
> auto-disabled when a real console (ttyS0 or ttySIF0) is available.
> This results in duplicate prints at boot-time after kernel starts
> using real console (i.e. ttyS0 or ttySIF0) if "earlycon=" kernel
> parameter was passed by bootloader.
>
> The reason for above issue is that RISCV SBI console always adds
> itself as preferred console which is causing other real consoles
> to be not used as preferred console.

Do we even need HVC_SBI console to be enabled by default? Disabling 
CONFIG_HVC_RISCV_SBI seems to be fine while running in QEMU.

If we don't need it, I suggest we should remove the config option from 
defconfig in addition to this patch.

Regards,
Atish
> Ideally "console=" kernel parameter passed by bootloaders should
> be the one selecting a preferred real console.
>
> This patch fixes above issue by not forcing RISCV SBI console as
> preferred console.
>
> Fixes: afa6b1ccfad5 ("tty: New RISC-V SBI console driver")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Anup Patel <anup.patel@xxxxxxx>
> ---
>   drivers/tty/hvc/hvc_riscv_sbi.c | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/drivers/tty/hvc/hvc_riscv_sbi.c b/drivers/tty/hvc/hvc_riscv_sbi.c
> index 75155bde2b88..31f53fa77e4a 100644
> --- a/drivers/tty/hvc/hvc_riscv_sbi.c
> +++ b/drivers/tty/hvc/hvc_riscv_sbi.c
> @@ -53,7 +53,6 @@ device_initcall(hvc_sbi_init);
>   static int __init hvc_sbi_console_init(void)
>   {
>   	hvc_instantiate(0, 0, &hvc_sbi_ops);
> -	add_preferred_console("hvc", 0, NULL);
>   
>   	return 0;
>   }