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From:   Sherry Sun <sherry.sun@nxp.com>
To:     =?iso-8859-1?Q?Ilpo_J=E4rvinen?= <ilpo.jarvinen@linux.intel.com>
CC:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Lukas Wunner <lukas@wunner.de>,
        linux-serial <linux-serial@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        dl-linux-imx <linux-imx@nxp.com>
Subject: RE: [PATCH] Revert "serial: fsl_lpuart: Reset prior to registration"
Thread-Topic: [PATCH] Revert "serial: fsl_lpuart: Reset prior to registration"
Thread-Index: AQHY0+EeaAH9c/DrIUi1YG5YmLZWk632OyYAgAAB3mA=
Date:   Thu, 29 Sep 2022 11:10:22 +0000
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 <1265873d-28f9-d39c-5cce-858dbed1e8e8@linux.intel.com>
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>=20
> > This reverts commit 60f361722ad2ae5ee667d0b0545d40c42f754daf.
> >
> > commit 60f361722ad2 ("serial: fsl_lpuart: Reset prior to
> > registration") causes the lpuart console cannot work any more. Since
> > the console is registered in the uart_add_one_port(), the driver
> > cannot identify the console port before call uart_add_one_port(),
> > which causes all the uart ports including the console port will be glob=
al
> reset.
> > So need to revert this patch to avoid breaking the lpuart console.
> >
> > Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
> > ---
> >  drivers/tty/serial/fsl_lpuart.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/tty/serial/fsl_lpuart.c
> > b/drivers/tty/serial/fsl_lpuart.c index 67fa113f77d4..7da46557fcb3
> > 100644
> > --- a/drivers/tty/serial/fsl_lpuart.c
> > +++ b/drivers/tty/serial/fsl_lpuart.c
> > @@ -2722,10 +2722,6 @@ static int lpuart_probe(struct platform_device
> *pdev)
> >  		handler =3D lpuart_int;
> >  	}
> >
> > -	ret =3D lpuart_global_reset(sport);
> > -	if (ret)
> > -		goto failed_reset;
> > -
>=20
> So the problem with this being so early is uart_console() in
> lpuart_global_reset() that doesn't detect a console because sport->cons i=
s
> not yet assigned? Couldn't that be worked around differently?
>=20
> Or is there something else in addition to that I'm missing?
>=20
Hi Ilpo,

Yes, the root cause of the console cannot work after apply the commit 60f36=
1722ad2 ("serial: fsl_lpuart: Reset prior to registration") is lpuart_globa=
l_reset() cannot identify the console port, so reset all uart ports.

Actually I've been thinking about any other workaround all afternoon, seems=
 no other good options to me till now. And after a further check, I think t=
he original patch is not needed, as uart_add_one_port() won't open the tty =
device, it should be safe to global reset the non-console ports after uart_=
add_one_port().

Best Regards
Sherry