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Date:   Fri, 15 Sep 2023 22:21:22 +0200
From:   Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To:     John Ogness <john.ogness@linutronix.de>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Marek Vasut <marex@denx.de>, Petr Mladek <pmladek@suse.com>,
        Fabio Estevam <festevam@gmail.com>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Rob Herring <robh@kernel.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Tom Rix <trix@redhat.com>, linux-kernel@vger.kernel.org,
        Sergey Organov <sorganov@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        linux-serial@vger.kernel.org,
        Ilpo =?utf-8?B?SsOkcnZpbmVu?= <ilpo.jarvinen@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Shawn Guo <shawnguo@kernel.org>,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH tty v1 29/74] serial: imx: Use port lock wrappers
Message-ID: <20230915202122.ulgy4fdxpsxmecbo@pengutronix.de>
References: <20230914183831.587273-1-john.ogness@linutronix.de>
 <20230914183831.587273-30-john.ogness@linutronix.de>
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On Thu, Sep 14, 2023 at 08:43:46PM +0206, John Ogness wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
>=20
> 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.
>=20
> 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 function
> to make informed decisions and eventually to restore operational state. It
> also allows to prevent the regular UART code from modifying UART registers
> while printk output is in progress.
>=20
> All modifications of UART registers are guarded by the UART port lock,
> which provides an obvious synchronization point with the console
> infrastructure.
>=20
> 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.
>=20
> Converted with coccinelle. No functional change.
>=20
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

This lacks a Signed-off line by John.

Otherwise looks fine to me.

Best regards
Uwe

--=20
Pengutronix e.K.                           | Uwe Kleine-K=F6nig            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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