Fix/revpi 1644/mainline rs485 support

drivers/tty/serial/amba-pl011.c

@@ -41,7 +41,6 @@
 #include <linux/sizes.h>
 #include <linux/io.h>
 #include <linux/acpi.h>
-#include <linux/gpio/consumer.h>
 
 #include "amba-pl011.h"
 
@@ -266,8 +265,8 @@ struct uart_amba_port {
 	unsigned int		old_cr;		/* state during shutdown */
 	unsigned int		fixed_baud;	/* vendor-set fixed baud rate */
 	char			type[12];
-	bool 			rs485_tx_started;
-	unsigned long		rs485_tx_drain_interval; /* average tx queue drain time in usecs */
+	bool			rs485_tx_started;
+	unsigned int		rs485_tx_drain_interval; /* usecs */
 #ifdef CONFIG_DMA_ENGINE
 	/* DMA stuff */
 	bool			using_tx_dma;
@@ -1289,14 +1288,23 @@ static inline bool pl011_dma_rx_running(struct uart_amba_port *uap)
 #define pl011_dma_flush_buffer	NULL
 #endif
 
-static int pl011_rs485_tx_stop(struct uart_amba_port *uap)
+static void pl011_rs485_tx_stop(struct uart_amba_port *uap)
 {
 	struct uart_port *port = &uap->port;
+	int i = 0;
 	u32 cr;
 
-	/* wait until hardware tx queue is empty */
-	while (!pl011_tx_empty(port))
+	/* Wait until hardware tx queue is empty */
+	while (!pl011_tx_empty(port)) {
+		if (i == port->fifosize) {
+			dev_warn(port->dev,
+				 "timeout while draining hardware tx queue\n");
+			break;
+		}
+
 		udelay(uap->rs485_tx_drain_interval);
+		i++;
+	}
 
 	if (port->rs485.delay_rts_after_send)
 		mdelay(port->rs485.delay_rts_after_send);
@@ -1308,13 +1316,12 @@ static int pl011_rs485_tx_stop(struct uart_amba_port *uap)
 	else
 		cr |= UART011_CR_RTS;
 
-	cr &= ~UART011_CR_TXE;		/* disable transmitter */
-	cr |= UART011_CR_RXE;		/* enable receiver */
+	/* Disable the transmitter and reenable the transceiver */
+	cr &= ~UART011_CR_TXE;
+	cr |= UART011_CR_RXE;
 	pl011_write(cr, uap, REG_CR);
 
 	uap->rs485_tx_started = false;
-
-	return 0;
 }
 
 static void pl011_stop_tx(struct uart_port *port)
@@ -1449,17 +1456,18 @@ static void pl011_rs485_tx_start(struct uart_amba_port *uap)
 	struct uart_port *port = &uap->port;
 	u32 cr;
 
+	/* Enable transmitter */
 	cr = pl011_read(uap, REG_CR);
-	cr |= UART011_CR_TXE;		/* re-enable transmitter */
+	cr |= UART011_CR_TXE;
 
+	/* Disable receiver if half-duplex */
 	if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))
-		cr &= ~UART011_CR_RXE;	/* disable receiver if half-duplex */
+		cr &= ~UART011_CR_RXE;
 
-	if (port->rs485.flags & SER_RS485_RTS_ON_SEND) {
+	if (port->rs485.flags & SER_RS485_RTS_ON_SEND)
 		cr &= ~UART011_CR_RTS;
-	} else {
+	else
 		cr |= UART011_CR_RTS;
-	}
 
 	pl011_write(cr, uap, REG_CR);
 
@@ -2071,6 +2079,7 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios,
 	unsigned int lcr_h, old_cr;
 	unsigned long flags;
 	unsigned int baud, quot, clkdiv;
+	unsigned int bits;
 
 	if (uap->vendor->oversampling)
 		clkdiv = 8;
@@ -2121,18 +2130,21 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios,
 	if (uap->fifosize > 1)
 		lcr_h |= UART01x_LCRH_FEN;
 
+	bits = tty_get_frame_size(termios->c_cflag);
+
 	spin_lock_irqsave(&port->lock, flags);
 
 	/*
 	 * Update the per-port timeout.
 	 */
 	uart_update_timeout(port, termios->c_cflag, baud);
-	/* Calculate the approximated maximum time it takes to drain the tx
-	   hardware queue with the given baud rate. Then use the half of this
-	   time to get the approximated time for the average case and use this
-	   as the poll interval when waiting for the queue to empty. */
-	uap->rs485_tx_drain_interval = jiffies_to_usecs(port->timeout) /
-				       uap->fifosize / 2;
+
+	/*
+	 * Calculate the approximated time it takes to transmit one character
+	 * with the given baud rate. We use this as the poll interval when we
+	 * wait for the tx queue to empty.
+	 */
+	uap->rs485_tx_drain_interval = (bits * 1000 * 1000) / baud;
 
 	pl011_setup_status_masks(port, termios);
 
@@ -2268,37 +2280,33 @@ static int pl011_rs485_config(struct uart_port *port,
 {
 	struct uart_amba_port *uap =
 		container_of(port, struct uart_amba_port, port);
-	bool terminate = false;
 
 	/* pick sane settings if the user hasn't */
-	if (!!(rs485->flags & SER_RS485_RTS_ON_SEND) ==
-	    !!(rs485->flags & SER_RS485_RTS_AFTER_SEND)) {
+	if (!(rs485->flags & SER_RS485_RTS_ON_SEND) ==
+	    !(rs485->flags & SER_RS485_RTS_AFTER_SEND)) {
 		rs485->flags |= SER_RS485_RTS_ON_SEND;
 		rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
 	}
-
-	rs485->delay_rts_before_send = min(rs485->delay_rts_before_send, 1000U);
-	rs485->delay_rts_after_send = min(rs485->delay_rts_after_send, 1000U);
+	/* clamp the delays to [0, 100ms] */
+	rs485->delay_rts_before_send = min(rs485->delay_rts_before_send, 100U);
+	rs485->delay_rts_after_send = min(rs485->delay_rts_after_send, 100U);
 	memset(rs485->padding, 0, sizeof(rs485->padding));
 
 	if (port->rs485.flags & SER_RS485_ENABLED)
 		pl011_rs485_tx_stop(uap);
 
 	/* Set new configuration */
 	port->rs485 = *rs485;
+
 	/* Make sure auto RTS is disabled */
 	if (port->rs485.flags & SER_RS485_ENABLED) {
 		u32 cr = pl011_read(uap, REG_CR);
+
 		cr &= ~UART011_CR_RTSEN;
 		pl011_write(cr, uap, REG_CR);
-
 		port->status &= ~UPSTAT_AUTORTS;
-		terminate = !!(rs485->flags & SER_RS485_TERMINATE_BUS);
 	}
 
-	if (port->rs485_term_gpio)
-		gpiod_set_value_cansleep(port->rs485_term_gpio, terminate);
-
 	return 0;
 }
 
@@ -2791,6 +2799,23 @@ static int pl011_find_free_port(void)
 	return -EBUSY;
 }
 
+static int pl011_get_rs485_mode(struct uart_amba_port *uap)
+{
+	struct uart_port *port = &uap->port;
+	struct serial_rs485 *rs485 = &port->rs485;
+	int ret;
+
+	ret = uart_get_rs485_mode(port);
+	if (ret)
+		return ret;
+
+	/* clamp the delays to [0, 100ms] */
+	rs485->delay_rts_before_send = min(rs485->delay_rts_before_send, 100U);
+	rs485->delay_rts_after_send = min(rs485->delay_rts_after_send, 100U);
+
+	return 0;
+}
+
 static int pl011_setup_port(struct device *dev, struct uart_amba_port *uap,
 			    struct resource *mmiobase, int index)
 {
@@ -2817,7 +2842,7 @@ static int pl011_setup_port(struct device *dev, struct uart_amba_port *uap,
 	uap->port.flags = UPF_BOOT_AUTOCONF;
 	uap->port.line = index;
 
-	ret = uart_get_rs485_mode(&uap->port);
+	ret = pl011_get_rs485_mode(uap);
 	if (ret)
 		return ret;
 

drivers/tty/serial/serial_core.c

@@ -334,39 +334,15 @@ void
 uart_update_timeout(struct uart_port *port, unsigned int cflag,
 		    unsigned int baud)
 {
-	unsigned int bits;
+	unsigned int size;
 
-	/* byte size and parity */
-	switch (cflag & CSIZE) {
-	case CS5:
-		bits = 7;
-		break;
-	case CS6:
-		bits = 8;
-		break;
-	case CS7:
-		bits = 9;
-		break;
-	default:
-		bits = 10;
-		break; /* CS8 */
-	}
-
-	if (cflag & CSTOPB)
-		bits++;
-	if (cflag & PARENB)
-		bits++;
-
-	/*
-	 * The total number of bits to be transmitted in the fifo.
-	 */
-	bits = bits * port->fifosize;
+	size = tty_get_frame_size(cflag) * port->fifosize;
 
 	/*
 	 * Figure the timeout to send the above number of bits.
 	 * Add .02 seconds of slop
 	 */
-	port->timeout = (HZ * bits) / baud + HZ/50;
+	port->timeout = (HZ * size) / baud + HZ/50;
 }
 
 EXPORT_SYMBOL(uart_update_timeout);

drivers/tty/tty_ioctl.c

@@ -300,6 +300,51 @@ int tty_termios_hw_change(const struct ktermios *a, const struct ktermios *b)
 }
 EXPORT_SYMBOL(tty_termios_hw_change);
 
+/**
+ *	tty_get_char_size	-	get size of a character
+ *	@cflag: termios cflag value
+ *
+ *	Get the size (in bits) of a character depending on @cflag's %CSIZE
+ *	setting.
+ */
+unsigned char tty_get_char_size(unsigned int cflag)
+{
+	switch (cflag & CSIZE) {
+	case CS5:
+		return 5;
+	case CS6:
+		return 6;
+	case CS7:
+		return 7;
+	case CS8:
+	default:
+		return 8;
+	}
+}
+EXPORT_SYMBOL_GPL(tty_get_char_size);
+
+/**
+ *	tty_get_frame_size	-	get size of a frame
+ *	@cflag: termios cflag value
+ *
+ *	Get the size (in bits) of a frame depending on @cflag's %CSIZE, %CSTOPB,
+ *	and %PARENB setting. The result is a sum of character size, start and
+ *	stop bits -- one bit each -- second stop bit (if set), and parity bit
+ *	(if set).
+ */
+unsigned char tty_get_frame_size(unsigned int cflag)
+{
+	unsigned char bits = 2 + tty_get_char_size(cflag);
+
+	if (cflag & CSTOPB)
+		bits++;
+	if (cflag & PARENB)
+		bits++;
+
+	return bits;
+}
+EXPORT_SYMBOL_GPL(tty_get_frame_size);
+
 /**
  *	tty_set_termios		-	update termios values
  *	@tty: tty to update

include/linux/tty.h

@@ -540,6 +540,9 @@ static inline speed_t tty_get_baud_rate(struct tty_struct *tty)
 	return tty_termios_baud_rate(&tty->termios);
 }
 
+unsigned char tty_get_char_size(unsigned int cflag);
+unsigned char tty_get_frame_size(unsigned int cflag);
+
 extern void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old);
 extern int tty_termios_hw_change(const struct ktermios *a, const struct ktermios *b);
 extern int tty_set_termios(struct tty_struct *tty, struct ktermios *kt);