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From:   Raviteja Narayanam <rna@xilinx.com>
To:     Maarten Brock <m.brock@vanmierlo.com>
CC:     "linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
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        "linux-serial-owner@vger.kernel.org" 
        <linux-serial-owner@vger.kernel.org>
Subject: RE: [PATCH] serial: uartps: Wait for tx_empty in console setup
Thread-Topic: [PATCH] serial: uartps: Wait for tx_empty in console setup
Thread-Index: AQHWDP0l3OgsBXnKvUufxZn7tcNQPqhvYOQAgADmX/A=
Date:   Thu, 9 Apr 2020 05:39:18 +0000
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Hi Maarten,

Thanks for the review.

> -----Original Message-----
> From: linux-serial-owner@vger.kernel.org <linux-serial-
> owner@vger.kernel.org> On Behalf Of Maarten Brock
> Sent: Wednesday, April 8, 2020 9:21 PM
> To: Raviteja Narayanam <rna@xilinx.com>
> Cc: linux-serial@vger.kernel.org; gregkh@linuxfoundation.org;
> jslaby@suse.com; Michal Simek <michals@xilinx.com>; linux-arm-
> kernel@lists.infradead.org; linux-kernel@vger.kernel.org; git <git@xilinx=
.com>;
> linux-serial-owner@vger.kernel.org
> Subject: Re: [PATCH] serial: uartps: Wait for tx_empty in console setup
>=20
> On 2020-04-07 18:53, Raviteja Narayanam wrote:
> > On some platforms, the log is corrupted while console is being
> > registered. It is observed that when set_termios is called, there are
> > still some bytes in the FIFO to be transmitted.
> >
> > So, wait for tx_empty inside cdns_uart_console_setup before calling
> > set_termios.
> >
> > Signed-off-by: Raviteja Narayanam <raviteja.narayanam@xilinx.com>
> > ---
> >  drivers/tty/serial/xilinx_uartps.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/tty/serial/xilinx_uartps.c
> > b/drivers/tty/serial/xilinx_uartps.c
> > index 6b26f76..23468ff 100644
> > --- a/drivers/tty/serial/xilinx_uartps.c
> > +++ b/drivers/tty/serial/xilinx_uartps.c
> > @@ -1260,6 +1260,8 @@ static int cdns_uart_console_setup(struct
> > console *co, char *options)
> >  	int bits =3D 8;
> >  	int parity =3D 'n';
> >  	int flow =3D 'n';
> > +	unsigned long time_out =3D jiffies + usecs_to_jiffies(TX_TIMEOUT);
> > +	int status;
> >
> >  	if (!port->membase) {
> >  		pr_debug("console on " CDNS_UART_TTY_NAME "%i not
> present\n", @@
> > -1270,6 +1272,14 @@ static int cdns_uart_console_setup(struct console
> > *co, char *options)
> >  	if (options)
> >  		uart_parse_options(options, &baud, &parity, &bits, &flow);
> >
> > +	/* Wait for tx_empty before setting up the console */
> > +	while (time_before(jiffies, time_out)) {
> > +		status =3D cdns_uart_tx_empty(port);
> > +		if (status =3D=3D TIOCSER_TEMT)
> > +			break;
> > +		cpu_relax();
> > +	}
> > +
> >  	return uart_set_options(port, co, baud, parity, bits, flow);  }
> > #endif /* CONFIG_SERIAL_XILINX_PS_UART_CONSOLE */
>=20
> You could do without the status variable. You could even combine the whil=
e
> and if conditions.
>=20
> And while you're at it, you might as well also rewrite the lines
> 1236-1238 to also use cdns_uart_tx_empty() for clarity.

Will send v2, addressing these.
>=20
> Maarten

Regards,
Raviteja N