linux-kernel - Re: [PATCH v2 1/2] serial: imx: fix detach/attach of serial console

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Date:   Wed, 20 Oct 2021 22:54:26 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Francesco Dolcini <francesco.dolcini@...adex.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Stefan Agner <stefan@...er.ch>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH v2 1/2] serial: imx: fix detach/attach of serial console

On Wed, Oct 20, 2021 at 10:27 PM Francesco Dolcini
<francesco.dolcini@...adex.com> wrote:
>
> From: Stefan Agner <stefan@...er.ch>
>
> If the device used as a serial console gets detached/attached at runtime,
> register_console() will try to call imx_uart_setup_console(), but this
> is not possible since it is marked as __init.

Thank you for fixing this!

> For instance
>
>   # cat /sys/devices/virtual/tty/console/active
>   tty1 ttymxc0
>   # echo -n N > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console
>   # echo -n Y > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console

Can we leave only something like below in the commit message?

> [   73.167005] Unable to handle kernel paging request at virtual address c154d928
> [   73.168304] Internal error: Oops: 8000000d [#1] SMP ARM
> [   73.168522] CPU: 0 PID: 536 Comm: sh Not tainted 5.15.0-rc6-00056-g3968ddcf05fb #3
  ...
> [   73.168791] PC is at imx_uart_console_setup+0x0/0x238
> [   73.168927] LR is at try_enable_new_console+0x98/0x124
  ...
> [   73.173826] [<c0196f44>] (try_enable_new_console) from [<c01984a8>] (register_console+0x10c/0x2ec)
> [   73.174053] [<c01984a8>] (register_console) from [<c06e2c90>] (console_store+0x14c/0x168)
> [   73.174262] [<c06e2c90>] (console_store) from [<c0383718>] (kernfs_fop_write_iter+0x110/0x1cc)

> A similar issue could be triggered unbinding/binding the serial console

on unbinding/binding

> device [*].
>
> Drop __init so that imx_uart_setup_console() can be safely called at
> runtime.
>
> [*] https://lore.kernel.org/all/20181114174940.7865-3-stefan@agner.ch/

Make it Link: tag?

> Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console")
> Signed-off-by: Stefan Agner <stefan@...er.ch>
> Signed-off-by: Francesco Dolcini <francesco.dolcini@...adex.com>

With above nit-picks addressed, FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

-- 
With Best Regards,
Andy Shevchenko