linux-kernel - RE: [PATCH 05/14] serial: tegra: flush the RX fifo on frame error

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Date:   Tue, 27 Aug 2019 09:29:41 +0000
From:   Krishna Yarlagadda <kyarlagadda@...dia.com>
To:     Thierry Reding <thierry.reding@...il.com>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        "Laxman Dewangan" <ldewangan@...dia.com>,
        "jslaby@...e.com" <jslaby@...e.com>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Shardar Mohammed" <smohammed@...dia.com>
Subject: RE: [PATCH 05/14] serial: tegra: flush the RX fifo on frame error

> -----Original Message-----
> From: Thierry Reding <thierry.reding@...il.com>
> Sent: Tuesday, August 13, 2019 3:19 PM
> To: Krishna Yarlagadda <kyarlagadda@...dia.com>
> Cc: gregkh@...uxfoundation.org; robh+dt@...nel.org;
> mark.rutland@....com; Jonathan Hunter <jonathanh@...dia.com>; Laxman
> Dewangan <ldewangan@...dia.com>; jslaby@...e.com; linux-
> serial@...r.kernel.org; devicetree@...r.kernel.org; linux-
> tegra@...r.kernel.org; linux-kernel@...r.kernel.org; Shardar Mohammed
> <smohammed@...dia.com>
> Subject: Re: [PATCH 05/14] serial: tegra: flush the RX fifo on frame error
> 
> On Mon, Aug 12, 2019 at 04:58:14PM +0530, Krishna Yarlagadda wrote:
> > From: Shardar Shariff Md <smohammed@...dia.com>
> >
> > FIFO reset/flush code implemented now does not follow programming
> > guidelines. RTS line has to be turned off while flushing fifos to
> > avoid new transfers. Also check LSR bits UART_LSR_TEMT and
> UART_LSR_DR
> > to confirm fifos are flushed.
> 
> You use inconsistent spelling for FIFO here.
Will fix in next version and take care of this in all patches

> 
> > Signed-off-by: Shardar Shariff Md <smohammed@...dia.com>
> > Signed-off-by: Krishna Yarlagadda <kyarlagadda@...dia.com>
> > ---
> >  drivers/tty/serial/serial-tegra.c | 15 +++++++++++++++
> >  1 file changed, 15 insertions(+)
> >
> > diff --git a/drivers/tty/serial/serial-tegra.c
> > b/drivers/tty/serial/serial-tegra.c
> > index ae7225c..f6a3f4e 100644
> > --- a/drivers/tty/serial/serial-tegra.c
> > +++ b/drivers/tty/serial/serial-tegra.c
> > @@ -266,6 +266,10 @@ static void tegra_uart_wait_sym_time(struct
> > tegra_uart_port *tup,  static void tegra_uart_fifo_reset(struct
> > tegra_uart_port *tup, u8 fcr_bits)  {
> >  	unsigned long fcr = tup->fcr_shadow;
> > +	unsigned int lsr, tmout = 10000;
> > +
> > +	if (tup->rts_active)
> > +		set_rts(tup, false);
> >
> >  	if (tup->cdata->allow_txfifo_reset_fifo_mode) {
> >  		fcr |= fcr_bits & (UART_FCR_CLEAR_RCVR |
> UART_FCR_CLEAR_XMIT); @@
> > -289,6 +293,17 @@ static void tegra_uart_fifo_reset(struct tegra_uart_port
> *tup, u8 fcr_bits)
> >  	 * to propagate, otherwise data could be lost.
> >  	 */
> >  	tegra_uart_wait_cycle_time(tup, 32);
> > +
> > +	do {
> > +		lsr = tegra_uart_read(tup, UART_LSR);
> > +		if (lsr | UART_LSR_TEMT)
> > +			if (!(lsr & UART_LSR_DR))
> 
> Can't both of these go on the same line?
> 
> Thierry
> 
They can be. Will fix in next version
KY

> > +				break;
> > +		udelay(1);
> > +	} while (--tmout);
> > +
> > +	if (tup->rts_active)
> > +		set_rts(tup, true);
> >  }
> >
> >  static int tegra_set_baudrate(struct tegra_uart_port *tup, unsigned
> > int baud)
> > --
> > 2.7.4
> >