From 7d25ca02c11d60137c936991edb488b44208877f Mon Sep 17 00:00:00 2001
From: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Date: Wed, 11 Jan 2017 16:43:38 +0200
Subject: [PATCH 224/255] serial: sh-sci: Remove manual break debouncing

The sh-sci driver implements manual break debouncing for a few SH
platforms by reading the value of the RX pin port register. This feature
is optional and the driver considers all negative or zero values of the
platform data port_reg field as invalid. As the four platforms that set
the field to a register address all use an address higher than
0x7fffffff, the driver will always consider the value as invalid and
never perform debouncing. The feature is unused, remove it.

Debouncing could be implemented properly in the future using the pinctrl
and GPIO APIs if desired.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit d5cb1319a91d4f1328b1c70b82c5899acd96af85)
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
---
 drivers/tty/serial/sh-sci.c |  124 ++------------------------------------------
 include/linux/serial_sci.h  |    5 -
 2 files changed, 7 insertions(+), 122 deletions(-)

--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -125,10 +125,6 @@ struct sci_port {
 	resource_size_t		reg_size;
 	struct mctrl_gpios	*gpios;
 
-	/* Break timer */
-	struct timer_list	break_timer;
-	int			break_flag;
-
 	/* Clocks */
 	struct clk		*clks[SCI_NUM_CLKS];
 	unsigned long		clk_rates[SCI_NUM_CLKS];
@@ -517,14 +513,6 @@ static void sci_port_disable(struct sci_
 	if (!sci_port->port.dev)
 		return;
 
-	/* Cancel the break timer to ensure that the timer handler will not try
-	 * to access the hardware with clocks and power disabled. Reset the
-	 * break flag to make the break debouncing state machine ready for the
-	 * next break.
-	 */
-	del_timer_sync(&sci_port->break_timer);
-	sci_port->break_flag = 0;
-
 	for (i = SCI_NUM_CLKS; i-- > 0; )
 		clk_disable_unprepare(sci_port->clks[i]);
 
@@ -751,20 +739,6 @@ static int sci_rxfill(struct uart_port *
 	return (serial_port_in(port, SCxSR) & SCxSR_RDxF(port)) != 0;
 }
 
-/*
- * SCI helper for checking the state of the muxed port/RXD pins.
- */
-static inline int sci_rxd_in(struct uart_port *port)
-{
-	struct sci_port *s = to_sci_port(port);
-
-	if (s->cfg->port_reg <= 0)
-		return 1;
-
-	/* Cast for ARM damage */
-	return !!__raw_readb((void __iomem *)(uintptr_t)s->cfg->port_reg);
-}
-
 /* ********************************************************************** *
  *                   the interrupt related routines                       *
  * ********************************************************************** */
@@ -832,7 +806,6 @@ static void sci_transmit_chars(struct ua
 
 static void sci_receive_chars(struct uart_port *port)
 {
-	struct sci_port *sci_port = to_sci_port(port);
 	struct tty_port *tport = &port->state->port;
 	int i, count, copied = 0;
 	unsigned short status;
@@ -852,8 +825,7 @@ static void sci_receive_chars(struct uar
 
 		if (port->type == PORT_SCI) {
 			char c = serial_port_in(port, SCxRDR);
-			if (uart_handle_sysrq_char(port, c) ||
-			    sci_port->break_flag)
+			if (uart_handle_sysrq_char(port, c))
 				count = 0;
 			else
 				tty_insert_flip_char(tport, c, TTY_NORMAL);
@@ -862,25 +834,6 @@ static void sci_receive_chars(struct uar
 				char c = serial_port_in(port, SCxRDR);
 
 				status = serial_port_in(port, SCxSR);
-#if defined(CONFIG_CPU_SH3)
-				/* Skip "chars" during break */
-				if (sci_port->break_flag) {
-					if ((c == 0) &&
-					    (status & SCxSR_FER(port))) {
-						count--; i--;
-						continue;
-					}
-
-					/* Nonzero => end-of-break */
-					dev_dbg(port->dev, "debounce<%02x>\n", c);
-					sci_port->break_flag = 0;
-
-					if (STEPFN(c)) {
-						count--; i--;
-						continue;
-					}
-				}
-#endif /* CONFIG_CPU_SH3 */
 				if (uart_handle_sysrq_char(port, c)) {
 					count--; i--;
 					continue;
@@ -918,37 +871,6 @@ static void sci_receive_chars(struct uar
 	}
 }
 
-#define SCI_BREAK_JIFFIES (HZ/20)
-
-/*
- * The sci generates interrupts during the break,
- * 1 per millisecond or so during the break period, for 9600 baud.
- * So dont bother disabling interrupts.
- * But dont want more than 1 break event.
- * Use a kernel timer to periodically poll the rx line until
- * the break is finished.
- */
-static inline void sci_schedule_break_timer(struct sci_port *port)
-{
-	mod_timer(&port->break_timer, jiffies + SCI_BREAK_JIFFIES);
-}
-
-/* Ensure that two consecutive samples find the break over. */
-static void sci_break_timer(unsigned long data)
-{
-	struct sci_port *port = (struct sci_port *)data;
-
-	if (sci_rxd_in(&port->port) == 0) {
-		port->break_flag = 1;
-		sci_schedule_break_timer(port);
-	} else if (port->break_flag == 1) {
-		/* break is over. */
-		port->break_flag = 2;
-		sci_schedule_break_timer(port);
-	} else
-		port->break_flag = 0;
-}
-
 static int sci_handle_errors(struct uart_port *port)
 {
 	int copied = 0;
@@ -968,35 +890,13 @@ static int sci_handle_errors(struct uart
 	}
 
 	if (status & SCxSR_FER(port)) {
-		if (sci_rxd_in(port) == 0) {
-			/* Notify of BREAK */
-			struct sci_port *sci_port = to_sci_port(port);
-
-			if (!sci_port->break_flag) {
-				port->icount.brk++;
-
-				sci_port->break_flag = 1;
-				sci_schedule_break_timer(sci_port);
-
-				/* Do sysrq handling. */
-				if (uart_handle_break(port))
-					return 0;
-
-				dev_dbg(port->dev, "BREAK detected\n");
-
-				if (tty_insert_flip_char(tport, 0, TTY_BREAK))
-					copied++;
-			}
-
-		} else {
-			/* frame error */
-			port->icount.frame++;
+		/* frame error */
+		port->icount.frame++;
 
-			if (tty_insert_flip_char(tport, 0, TTY_FRAME))
-				copied++;
+		if (tty_insert_flip_char(tport, 0, TTY_FRAME))
+			copied++;
 
-			dev_notice(port->dev, "frame error\n");
-		}
+		dev_notice(port->dev, "frame error\n");
 	}
 
 	if (status & SCxSR_PER(port)) {
@@ -1049,17 +949,11 @@ static int sci_handle_breaks(struct uart
 	int copied = 0;
 	unsigned short status = serial_port_in(port, SCxSR);
 	struct tty_port *tport = &port->state->port;
-	struct sci_port *s = to_sci_port(port);
 
 	if (uart_handle_break(port))
 		return 0;
 
-	if (!s->break_flag && status & SCxSR_BRK(port)) {
-#if defined(CONFIG_CPU_SH3)
-		/* Debounce break */
-		s->break_flag = 1;
-#endif
-
+	if (status & SCxSR_BRK(port)) {
 		port->icount.brk++;
 
 		/* Notify of BREAK */
@@ -2683,10 +2577,6 @@ static int sci_init_single(struct platfo
 		pm_runtime_enable(&dev->dev);
 	}
 
-	sci_port->break_timer.data = (unsigned long)sci_port;
-	sci_port->break_timer.function = sci_break_timer;
-	init_timer(&sci_port->break_timer);
-
 	port->type		= p->type;
 	port->flags		= UPF_FIXED_PORT | UPF_BOOT_AUTOCONF | p->flags;
 	port->regshift		= p->regshift;
--- a/include/linux/serial_sci.h
+++ b/include/linux/serial_sci.h
@@ -9,8 +9,6 @@
  * Generic header for SuperH (H)SCI(F) (used by sh/sh64 and related parts)
  */
 
-#define SCIx_NOT_SUPPORTED	(-1)
-
 /* Serial Control Register (@ = not supported by all parts) */
 #define SCSCR_TIE	BIT(7)	/* Transmit Interrupt Enable */
 #define SCSCR_RIE	BIT(6)	/* Receive Interrupt Enable */
@@ -41,8 +39,6 @@ enum {
 	SCIx_NR_REGTYPES,
 };
 
-struct device;
-
 struct plat_sci_port_ops {
 	void (*init_pins)(struct uart_port *, unsigned int cflag);
 };
@@ -66,7 +62,6 @@ struct plat_sci_port {
 	/*
 	 * Platform overrides if necessary, defaults otherwise.
 	 */
-	int		port_reg;
 	unsigned char	regshift;
 	unsigned char	regtype;