[PATCH 1/7] mxser: restore baud rate if its setting fails

[PATCH 1/7] mxser: restore baud rate if its setting fails

[Jiri Slaby]

If a user tries to set a too high rate, it fails due to check in
mxser_set_baud(). But the high rate remains set in termios, so the user
might think everything went smooth. Restore the baud rate from the
old_termios if this happens, so that user knows nothing was changed in
fact.

It used to behave the correct way many years ago, but somehow the
restoration vanished with commit 1c45607ad3eb (Char: mxser, remove it)
-- the commit removed mxser's older clone.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/tty/mxser.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index 1216f3985e18..b9cc41782ce1 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -559,14 +559,20 @@ static void mxser_handle_cts(struct tty_struct *tty, struct mxser_port *info,
  * This routine is called to set the UART divisor registers to match
  * the specified baud rate for a serial port.
  */
-static void mxser_change_speed(struct tty_struct *tty)
+static void mxser_change_speed(struct tty_struct *tty, struct ktermios *old_termios)
 {
 	struct mxser_port *info = tty->driver_data;
 	unsigned cflag, cval, fcr;
 
 	cflag = tty->termios.c_cflag;
 
-	mxser_set_baud(tty, tty_get_baud_rate(tty));
+	if (mxser_set_baud(tty, tty_get_baud_rate(tty))) {
+		/* Use previous rate on a failure */
+		if (old_termios) {
+			speed_t baud = tty_termios_baud_rate(old_termios);
+			tty_encode_baud_rate(tty, baud, baud);
+		}
+	}
 
 	/* byte size and parity */
 	switch (cflag & CSIZE) {
@@ -791,7 +797,7 @@ static int mxser_activate(struct tty_port *port, struct tty_struct *tty)
 	/*
 	 * and set the speed of the serial port
 	 */
-	mxser_change_speed(tty);
+	mxser_change_speed(tty, NULL);
 	spin_unlock_irqrestore(&info->slock, flags);
 
 	return 0;
@@ -1119,7 +1125,7 @@ static int mxser_set_serial_info(struct tty_struct *tty,
 	if (tty_port_initialized(port)) {
 		if (old_speed != (port->flags & ASYNC_SPD_MASK)) {
 			spin_lock_irqsave(&info->slock, sl_flags);
-			mxser_change_speed(tty);
+			mxser_change_speed(tty, NULL);
 			spin_unlock_irqrestore(&info->slock, sl_flags);
 		}
 	} else {
@@ -1425,7 +1431,7 @@ static void mxser_set_termios(struct tty_struct *tty, struct ktermios *old_termi
 	unsigned long flags;
 
 	spin_lock_irqsave(&info->slock, flags);
-	mxser_change_speed(tty);
+	mxser_change_speed(tty, old_termios);
 	spin_unlock_irqrestore(&info->slock, flags);
 
 	if ((old_termios->c_cflag & CRTSCTS) && !C_CRTSCTS(tty)) {
-- 
2.33.0

[PATCH 2/7] mxser: simplify condition in mxser_receive_chars_new

[Jiri Slaby]

mxser_receive_chars_old() is used whenever MOXA_MUST_LSR_RERR is set in
status no matter the HW ID (the last 'if'). So there is no need for
another check of MOXA_MUST_LSR_RERR _with_ hwid == MOXA_MUST_MU860_HWID
(the third 'if').  Hence remove this subcase. That allows us to check
status on a single line with both UART_LSR_BRK_ERROR_BITS (from the
second 'if') and MOXA_MUST_LSR_RERR (the last 'if').

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/tty/mxser.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index b9cc41782ce1..f907de56e08b 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -1550,11 +1550,7 @@ static bool mxser_receive_chars_new(struct tty_struct *tty,
 
 	if (hwid == MOXA_OTHER_UART)
 		return false;
-	if (status & UART_LSR_BRK_ERROR_BITS)
-		return false;
-	if (hwid == MOXA_MUST_MU860_HWID && (status & MOXA_MUST_LSR_RERR))
-		return false;
-	if (status & MOXA_MUST_LSR_RERR)
+	if (status & (UART_LSR_BRK_ERROR_BITS | MOXA_MUST_LSR_RERR))
 		return false;
 
 	gdl = inb(port->ioaddr + MOXA_MUST_GDL_REGISTER);
-- 
2.33.0

[PATCH 3/7] mxser: make mxser_port::ldisc_stop_rx a bool

[Jiri Slaby]

It's used only as a yes-no variable, so make it a bool and switch the
set values appropriately.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/tty/mxser.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index f907de56e08b..309acf3f1ec3 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -250,7 +250,7 @@ struct mxser_port {
 	u8 IER;			/* Interrupt Enable Register */
 	u8 MCR;			/* Modem control register */
 
-	unsigned char ldisc_stop_rx;
+	bool ldisc_stop_rx;
 
 	struct async_icount icount; /* kernel counters for 4 input interrupts */
 	unsigned int timeout;
@@ -1341,7 +1341,7 @@ static void mxser_stoprx(struct tty_struct *tty)
 {
 	struct mxser_port *info = tty->driver_data;
 
-	info->ldisc_stop_rx = 1;
+	info->ldisc_stop_rx = true;
 	if (I_IXOFF(tty)) {
 		if (info->board->must_hwid) {
 			info->IER &= ~MOXA_MUST_RECV_ISR;
@@ -1374,7 +1374,7 @@ static void mxser_unthrottle(struct tty_struct *tty)
 	struct mxser_port *info = tty->driver_data;
 
 	/* startrx */
-	info->ldisc_stop_rx = 0;
+	info->ldisc_stop_rx = false;
 	if (I_IXOFF(tty)) {
 		if (info->x_char)
 			info->x_char = 0;
@@ -1849,7 +1849,7 @@ static void mxser_initbrd(struct mxser_board *brd, bool high_baud)
 		tty_port_init(&info->port);
 		info->port.ops = &mxser_port_ops;
 		info->board = brd;
-		info->ldisc_stop_rx = 0;
+		info->ldisc_stop_rx = false;
 
 		/* Enhance mode enabled here */
 		if (brd->must_hwid != MOXA_OTHER_UART)
-- 
2.33.0

[PATCH 4/7] mxser: simplify FCR computation in mxser_change_speed()

[Jiri Slaby]

Provided FIFO is always enabled for MUST chips, move its FCR setting out
of PORT_8250/PORT_16450 special case in mxser_change_speed(). Now, we
can pre-set fcr to zero and invert the condition of the 'if'.

This makes the code more readable (no functional change intended).

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/tty/mxser.c | 47 +++++++++++++++++++--------------------------
 1 file changed, 20 insertions(+), 27 deletions(-)

diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index 309acf3f1ec3..c194a96bb14e 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -600,33 +600,26 @@ static void mxser_change_speed(struct tty_struct *tty, struct ktermios *old_term
 	if (cflag & CMSPAR)
 		cval |= UART_LCR_SPAR;
 
-	if ((info->type == PORT_8250) || (info->type == PORT_16450)) {
-		if (info->board->must_hwid) {
-			fcr = UART_FCR_ENABLE_FIFO;
-			fcr |= MOXA_MUST_FCR_GDA_MODE_ENABLE;
-			mxser_set_must_fifo_value(info);
-		} else
-			fcr = 0;
-	} else {
-		fcr = UART_FCR_ENABLE_FIFO;
-		if (info->board->must_hwid) {
-			fcr |= MOXA_MUST_FCR_GDA_MODE_ENABLE;
-			mxser_set_must_fifo_value(info);
-		} else {
-			switch (info->rx_high_water) {
-			case 1:
-				fcr |= UART_FCR_TRIGGER_1;
-				break;
-			case 4:
-				fcr |= UART_FCR_TRIGGER_4;
-				break;
-			case 8:
-				fcr |= UART_FCR_TRIGGER_8;
-				break;
-			default:
-				fcr |= UART_FCR_TRIGGER_14;
-				break;
-			}
+	fcr = 0;
+	if (info->board->must_hwid) {
+		fcr |= UART_FCR_ENABLE_FIFO |
+			MOXA_MUST_FCR_GDA_MODE_ENABLE;
+		mxser_set_must_fifo_value(info);
+	} else if (info->type != PORT_8250 && info->type != PORT_16450) {
+		fcr |= UART_FCR_ENABLE_FIFO;
+		switch (info->rx_high_water) {
+		case 1:
+			fcr |= UART_FCR_TRIGGER_1;
+			break;
+		case 4:
+			fcr |= UART_FCR_TRIGGER_4;
+			break;
+		case 8:
+			fcr |= UART_FCR_TRIGGER_8;
+			break;
+		default:
+			fcr |= UART_FCR_TRIGGER_14;
+			break;
 		}
 	}
 
-- 
2.33.0

[PATCH 5/7] mxser: move FIFO clearing to mxser_disable_and_clear_FIFO()

[Jiri Slaby]

This code is used on two places, make a helper for disabling and
clearing FIFOs. And demangle the too complicated 'if' by using a local
variable.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/tty/mxser.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index c194a96bb14e..6913a1caa6f0 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -706,6 +706,16 @@ static void mxser_check_modem_status(struct tty_struct *tty,
 		mxser_handle_cts(tty, port, status);
 }
 
+static void mxser_disable_and_clear_FIFO(struct mxser_port *info)
+{
+	u8 fcr = UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT;
+
+	if (info->board->must_hwid)
+		fcr |= MOXA_MUST_FCR_GDA_MODE_ENABLE;
+
+	outb(fcr, info->ioaddr + UART_FCR);
+}
+
 static int mxser_activate(struct tty_port *port, struct tty_struct *tty)
 {
 	struct mxser_port *info = container_of(port, struct mxser_port, port);
@@ -730,13 +740,7 @@ static int mxser_activate(struct tty_port *port, struct tty_struct *tty)
 	 * Clear the FIFO buffers and disable them
 	 * (they will be reenabled in mxser_change_speed())
 	 */
-	if (info->board->must_hwid)
-		outb((UART_FCR_CLEAR_RCVR |
-			UART_FCR_CLEAR_XMIT |
-			MOXA_MUST_FCR_GDA_MODE_ENABLE), info->ioaddr + UART_FCR);
-	else
-		outb((UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT),
-			info->ioaddr + UART_FCR);
+	mxser_disable_and_clear_FIFO(info);
 
 	/*
 	 * At this point there's no way the LSR could still be 0xFF;
@@ -824,13 +828,7 @@ static void mxser_shutdown_port(struct tty_port *port)
 	outb(0x00, info->ioaddr + UART_IER);
 
 	/* clear Rx/Tx FIFO's */
-	if (info->board->must_hwid)
-		outb(UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT |
-				MOXA_MUST_FCR_GDA_MODE_ENABLE,
-				info->ioaddr + UART_FCR);
-	else
-		outb(UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
-			info->ioaddr + UART_FCR);
+	mxser_disable_and_clear_FIFO(info);
 
 	/* read data port to reset things */
 	(void) inb(info->ioaddr + UART_RX);
-- 
2.33.0

[PATCH 6/7] mxser: don't read from UART_FCR

[Jiri Slaby]

The UART_FCR register is write-only. When reading it, one gets contents
of (read-only) UART_IIR instead as they are shared. This mistake was
performed in mxser_flush_buffer() to clear FIFOs.

Actually FCR handling throughout the driver is completely broken. On
many places, it respects neither mu860 settings, nor FIFO (16450 vs
16550) setting. This patch doesn't help to fix this, it actually does
the same. We will introduce a mxser_port::FCR in the next patch to fix
this issue.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/tty/mxser.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index 6913a1caa6f0..4ce21cdb1ea5 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -859,17 +859,14 @@ static int mxser_open(struct tty_struct *tty, struct file *filp)
 static void mxser_flush_buffer(struct tty_struct *tty)
 {
 	struct mxser_port *info = tty->driver_data;
-	char fcr;
 	unsigned long flags;
 
 
 	spin_lock_irqsave(&info->slock, flags);
 	info->xmit_cnt = info->xmit_head = info->xmit_tail = 0;
 
-	fcr = inb(info->ioaddr + UART_FCR);
-	outb((fcr | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT),
+	outb(UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
 		info->ioaddr + UART_FCR);
-	outb(fcr, info->ioaddr + UART_FCR);
 
 	spin_unlock_irqrestore(&info->slock, flags);
 
-- 
2.33.0

[PATCH 7/7] mxser: store FCR state in mxser_port::FCR

[Jiri Slaby]

We force the FCR contents on many places in the code instead of writing
what was actually set in mxser_change_speed() (by ->activate() or
->set_serial_info()).

So introduce mxser_port::FCR to hold the proper contents and bitwise-OR
the value to what needs to be set on all those locations. That is,
clearing RX and/or TX FIFOs. Those flags are self-clearing, so no need
to set them to mxser_port::FCR.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/tty/mxser.c | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index 4ce21cdb1ea5..93a95a135a71 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -249,6 +249,7 @@ struct mxser_port {
 	unsigned char x_char;	/* xon/xoff character */
 	u8 IER;			/* Interrupt Enable Register */
 	u8 MCR;			/* Modem control register */
+	u8 FCR;			/* FIFO control register */
 
 	bool ldisc_stop_rx;
 
@@ -562,7 +563,7 @@ static void mxser_handle_cts(struct tty_struct *tty, struct mxser_port *info,
 static void mxser_change_speed(struct tty_struct *tty, struct ktermios *old_termios)
 {
 	struct mxser_port *info = tty->driver_data;
-	unsigned cflag, cval, fcr;
+	unsigned cflag, cval;
 
 	cflag = tty->termios.c_cflag;
 
@@ -600,25 +601,25 @@ static void mxser_change_speed(struct tty_struct *tty, struct ktermios *old_term
 	if (cflag & CMSPAR)
 		cval |= UART_LCR_SPAR;
 
-	fcr = 0;
+	info->FCR = 0;
 	if (info->board->must_hwid) {
-		fcr |= UART_FCR_ENABLE_FIFO |
+		info->FCR |= UART_FCR_ENABLE_FIFO |
 			MOXA_MUST_FCR_GDA_MODE_ENABLE;
 		mxser_set_must_fifo_value(info);
 	} else if (info->type != PORT_8250 && info->type != PORT_16450) {
-		fcr |= UART_FCR_ENABLE_FIFO;
+		info->FCR |= UART_FCR_ENABLE_FIFO;
 		switch (info->rx_high_water) {
 		case 1:
-			fcr |= UART_FCR_TRIGGER_1;
+			info->FCR |= UART_FCR_TRIGGER_1;
 			break;
 		case 4:
-			fcr |= UART_FCR_TRIGGER_4;
+			info->FCR |= UART_FCR_TRIGGER_4;
 			break;
 		case 8:
-			fcr |= UART_FCR_TRIGGER_8;
+			info->FCR |= UART_FCR_TRIGGER_8;
 			break;
 		default:
-			fcr |= UART_FCR_TRIGGER_14;
+			info->FCR |= UART_FCR_TRIGGER_14;
 			break;
 		}
 	}
@@ -679,7 +680,7 @@ static void mxser_change_speed(struct tty_struct *tty, struct ktermios *old_term
 	}
 
 
-	outb(fcr, info->ioaddr + UART_FCR);	/* set fcr */
+	outb(info->FCR, info->ioaddr + UART_FCR);
 	outb(cval, info->ioaddr + UART_LCR);
 }
 
@@ -865,7 +866,7 @@ static void mxser_flush_buffer(struct tty_struct *tty)
 	spin_lock_irqsave(&info->slock, flags);
 	info->xmit_cnt = info->xmit_head = info->xmit_tail = 0;
 
-	outb(UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
+	outb(info->FCR | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
 		info->ioaddr + UART_FCR);
 
 	spin_unlock_irqrestore(&info->slock, flags);
@@ -1572,8 +1573,7 @@ static u8 mxser_receive_chars_old(struct tty_struct *tty,
 
 		ch = inb(port->ioaddr + UART_RX);
 		if (hwid && (status & UART_LSR_OE))
-			outb(UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR |
-					MOXA_MUST_FCR_GDA_MODE_ENABLE,
+			outb(port->FCR | UART_FCR_CLEAR_RCVR,
 					port->ioaddr + UART_FCR);
 		status &= port->read_status_mask;
 		if (status & port->ignore_status_mask) {
@@ -1685,8 +1685,7 @@ static bool mxser_port_isr(struct mxser_port *port)
 	tty = tty_port_tty_get(&port->port);
 	if (!tty || port->closing || !tty_port_initialized(&port->port)) {
 		status = inb(port->ioaddr + UART_LSR);
-		outb(MOXA_MUST_FCR_GDA_MODE_ENABLE | UART_FCR_ENABLE_FIFO |
-				UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
+		outb(port->FCR | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
 				port->ioaddr + UART_FCR);
 		inb(port->ioaddr + UART_MSR);
 
-- 
2.33.0