Commit 8d479237 authored by Lino Sanfilippo's avatar Lino Sanfilippo Committed by Greg Kroah-Hartman
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serial: amba-pl011: add RS485 support 



Add basic support for RS485: Provide a callback to configure RS485
settings. Handle the RS485 specific part in the functions
pl011_rs485_tx_start() and pl011_rs485_tx_stop() which extend the generic
start/stop callbacks.
Beside via IOCTL from userspace RS485 can be enabled by means of the
device tree property "rs485-enabled-at-boot-time".

Signed-off-by: default avatarLino Sanfilippo <LinoSanfilippo@gmx.de>
Link: https://lore.kernel.org/r/20210630225644.3744-1-LinoSanfilippo@gmx.de


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 240e126c

drivers/tty/serial/amba-pl011.c

+161 −2
Original line number Diff line number Diff line
@@ -265,6 +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 int		rs485_tx_drain_interval; /* usecs */

#ifdef CONFIG_DMA_ENGINE

	/* DMA stuff */

	bool			using_tx_dma;
@@ -275,6 +277,8 @@ struct uart_amba_port { 
#endif

};



static unsigned int pl011_tx_empty(struct uart_port *port);



static unsigned int pl011_reg_to_offset(const struct uart_amba_port *uap,

	unsigned int reg)

{
@@ -1282,6 +1286,42 @@ static inline bool pl011_dma_rx_running(struct uart_amba_port *uap) 
#define pl011_dma_flush_buffer	NULL

#endif



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)) {

		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);



	cr = pl011_read(uap, REG_CR);



	if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)

		cr &= ~UART011_CR_RTS;

	else

		cr |= UART011_CR_RTS;



	/* 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;

}



static void pl011_stop_tx(struct uart_port *port)

{

	struct uart_amba_port *uap =
@@ -1290,6 +1330,9 @@ static void pl011_stop_tx(struct uart_port *port) 
	uap->im &= ~UART011_TXIM;

	pl011_write(uap->im, uap, REG_IMSC);

	pl011_dma_tx_stop(uap);



	if ((port->rs485.flags & SER_RS485_ENABLED) && uap->rs485_tx_started)

		pl011_rs485_tx_stop(uap);

}



static bool pl011_tx_chars(struct uart_amba_port *uap, bool from_irq);
@@ -1380,6 +1423,32 @@ static bool pl011_tx_char(struct uart_amba_port *uap, unsigned char c, 
	return true;

}



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;



	/* Disable receiver if half-duplex */

	if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))

		cr &= ~UART011_CR_RXE;



	if (port->rs485.flags & SER_RS485_RTS_ON_SEND)

		cr &= ~UART011_CR_RTS;

	else

		cr |= UART011_CR_RTS;



	pl011_write(cr, uap, REG_CR);



	if (port->rs485.delay_rts_before_send)

		mdelay(port->rs485.delay_rts_before_send);



	uap->rs485_tx_started = true;

}



/* Returns true if tx interrupts have to be (kept) enabled  */

static bool pl011_tx_chars(struct uart_amba_port *uap, bool from_irq)

{
@@ -1397,6 +1466,10 @@ static bool pl011_tx_chars(struct uart_amba_port *uap, bool from_irq) 
		return false;

	}



	if ((uap->port.rs485.flags & SER_RS485_ENABLED) &&

	    !uap->rs485_tx_started)

		pl011_rs485_tx_start(uap);



	/* If we are using DMA mode, try to send some characters. */

	if (pl011_dma_tx_irq(uap))

		return true;
@@ -1542,6 +1615,9 @@ static void pl011_set_mctrl(struct uart_port *port, unsigned int mctrl) 
	    container_of(port, struct uart_amba_port, port);

	unsigned int cr;



	if (port->rs485.flags & SER_RS485_ENABLED)

		mctrl &= ~TIOCM_RTS;



	cr = pl011_read(uap, REG_CR);



#define	TIOCMBIT(tiocmbit, uartbit)		\
@@ -1763,7 +1839,17 @@ static int pl011_startup(struct uart_port *port) 


	/* restore RTS and DTR */

	cr = uap->old_cr & (UART011_CR_RTS | UART011_CR_DTR);

	cr |= UART01x_CR_UARTEN | UART011_CR_RXE | UART011_CR_TXE;

	cr |= UART01x_CR_UARTEN | UART011_CR_RXE;



	if (port->rs485.flags & SER_RS485_ENABLED) {

		if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)

			cr &= ~UART011_CR_RTS;

		else

			cr |= UART011_CR_RTS;

	} else {

		cr |= UART011_CR_TXE;

	}



	pl011_write(cr, uap, REG_CR);



	spin_unlock_irq(&uap->port.lock);
@@ -1864,6 +1950,9 @@ static void pl011_shutdown(struct uart_port *port) 


	pl011_dma_shutdown(uap);



	if ((port->rs485.flags & SER_RS485_ENABLED) && uap->rs485_tx_started)

		pl011_rs485_tx_stop(uap);



	free_irq(uap->port.irq, uap);



	pl011_disable_uart(uap);
@@ -1941,6 +2030,7 @@ 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;
@@ -1991,6 +2081,8 @@ 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);



	/*
@@ -1998,11 +2090,21 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios, 
	 */

	uart_update_timeout(port, termios->c_cflag, baud);



	/*

	 * 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);



	if (UART_ENABLE_MS(port, termios->c_cflag))

		pl011_enable_ms(port);



	if (port->rs485.flags & SER_RS485_ENABLED)

		termios->c_cflag &= ~CRTSCTS;



	/* first, disable everything */

	old_cr = pl011_read(uap, REG_CR);

	pl011_write(0, uap, REG_CR);
@@ -2124,6 +2226,41 @@ static int pl011_verify_port(struct uart_port *port, struct serial_struct *ser) 
	return ret;

}



static int pl011_rs485_config(struct uart_port *port,

			      struct serial_rs485 *rs485)

{

	struct uart_amba_port *uap =

		container_of(port, struct uart_amba_port, port);



	/* pick sane settings if the user hasn't */

	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;

	}

	/* 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;

	}



	return 0;

}



static const struct uart_ops amba_pl011_pops = {

	.tx_empty	= pl011_tx_empty,

	.set_mctrl	= pl011_set_mctrl,
@@ -2588,10 +2725,28 @@ 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)

{

	void __iomem *base;

	int ret;



	base = devm_ioremap_resource(dev, mmiobase);

	if (IS_ERR(base))
@@ -2608,6 +2763,10 @@ static int pl011_setup_port(struct device *dev, struct uart_amba_port *uap, 
	uap->port.flags = UPF_BOOT_AUTOCONF;

	uap->port.line = index;



	ret = pl011_get_rs485_mode(uap);

	if (ret)

		return ret;



	amba_ports[index] = uap;



	return 0;
@@ -2665,7 +2824,7 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id) 
	uap->port.iotype = vendor->access_32b ? UPIO_MEM32 : UPIO_MEM;

	uap->port.irq = dev->irq[0];

	uap->port.ops = &amba_pl011_pops;



	uap->port.rs485_config = pl011_rs485_config;

	snprintf(uap->type, sizeof(uap->type), "PL011 rev%u", amba_rev(dev));



	ret = pl011_setup_port(&dev->dev, uap, &dev->res, portnr);