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

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Date:   Fri, 26 Apr 2019 14:12:34 +0530
From:   Anup Patel <anup@...infault.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Atish Patra <atish.patra@....com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Anup Patel <Anup.Patel@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Jiri Slaby <jslaby@...e.com>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH] tty: Don't force RISCV SBI console as preferred console

On Fri, Apr 26, 2019 at 11:51 AM Christoph Hellwig <hch@...radead.org> wrote:
>
> On Thu, Apr 25, 2019 at 09:41:21PM -0700, Atish Patra wrote:
> > 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.
>
> I think the whole concept of the SBI console is a little dangerous.
> It means that for one piece of physical hardware (usually the uart)
> we have two entiries (the M-mode firmware and the OS) in control,
> which tends to rarely end well.

I think the SBI console is only useful for early SOC bringup and early
SOC debugging when most drivers are not available in upstream
kernel. It cannot (and should not) be used in production deployments.

Regards,
Anup