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References: <20230914183831.587273-1-john.ogness@linutronix.de> <20230914183831.587273-12-john.ogness@linutronix.de>
In-Reply-To: <20230914183831.587273-12-john.ogness@linutronix.de>
From:   Chen-Yu Tsai <wenst@chromium.org>
Date:   Fri, 15 Sep 2023 12:07:00 +0800
Message-ID: <CAGXv+5FNSBm170z-XffkfcfQaAw4XXH3NEkonKE2s4x8ewz7WQ@mail.gmail.com>
Subject: Re: [PATCH tty v1 11/74] serial: 8250_mtk: Use port lock wrappers
To:     John Ogness <john.ogness@linutronix.de>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        linux-serial@vger.kernel.org, Petr Mladek <pmladek@suse.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-kernel@vger.kernel.org,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        Tony Lindgren <tony@atomide.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org
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On Fri, Sep 15, 2023 at 2:38=E2=80=AFAM John Ogness <john.ogness@linutronix=
.de> wrote:
>
> From: Thomas Gleixner <tglx@linutronix.de>
>
> When a serial port is used for kernel console output, then all
> modifications to the UART registers which are done from other contexts,
> e.g. getty, termios, are interference points for the kernel console.
>
> So far this has been ignored and the printk output is based on the
> principle of hope. The rework of the console infrastructure which aims to
> support threaded and atomic consoles, requires to mark sections which
> modify the UART registers as unsafe. This allows the atomic write functio=
n
> to make informed decisions and eventually to restore operational state. I=
t
> also allows to prevent the regular UART code from modifying UART register=
s
> while printk output is in progress.
>
> All modifications of UART registers are guarded by the UART port lock,
> which provides an obvious synchronization point with the console
> infrastructure.
>
> To avoid adding this functionality to all UART drivers, wrap the
> spin_[un]lock*() invocations for uart_port::lock into helper functions
> which just contain the spin_[un]lock*() invocations for now. In a
> subsequent step these helpers will gain the console synchronization
> mechanisms.
>
> Converted with coccinelle. No functional change.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Replacements look correct.

Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>