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serial: ar933x_uart: add RS485 support

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Emulate half-duplex operation and use mctrl_gpio to add support for
RS485 tranceiver with transmit/receive switch hooked to RTS GPIO line.
This is needed to make use of the RS485 port found on Teltonika RUT955.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://lore.kernel.org/r/20200221212331.GA21467@makrotopia.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Daniel Golle 2020-02-21 22:23:31 +01:00 committed by Greg Kroah-Hartman
parent 9fa3c4b1fa
commit 9be1064fe5
2 changed files with 108 additions and 6 deletions
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1
drivers/tty/serial/Kconfig
View File

@ -1269,6 +1269,7 @@ config SERIAL_AR933X
tristate "AR933X serial port support"
depends on HAVE_CLK && ATH79
select SERIAL_CORE
select SERIAL_MCTRL_GPIO if GPIOLIB
help
If you have an Atheros AR933X SOC based board and want to use the
built-in UART of the SoC, say Y to this option.

113
drivers/tty/serial/ar933x_uart.c
View File

@ -13,6 +13,7 @@
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_platform.h>
@ -29,6 +30,8 @@
#include <asm/mach-ath79/ar933x_uart.h>
#include "serial_mctrl_gpio.h"
#define DRIVER_NAME "ar933x-uart"
#define AR933X_UART_MAX_SCALE 0xff
@ -47,6 +50,8 @@ struct ar933x_uart_port {
unsigned int min_baud;
unsigned int max_baud;
struct clk *clk;
struct mctrl_gpios *gpios;
struct gpio_desc *rts_gpiod;
};
static inline unsigned int ar933x_uart_read(struct ar933x_uart_port *up,
@ -100,6 +105,18 @@ static inline void ar933x_uart_stop_tx_interrupt(struct ar933x_uart_port *up)
ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
}
static inline void ar933x_uart_start_rx_interrupt(struct ar933x_uart_port *up)
{
up->ier |= AR933X_UART_INT_RX_VALID;
ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
}
static inline void ar933x_uart_stop_rx_interrupt(struct ar933x_uart_port *up)
{
up->ier &= ~AR933X_UART_INT_RX_VALID;
ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
}
static inline void ar933x_uart_putc(struct ar933x_uart_port *up, int ch)
{
unsigned int rdata;
@ -125,11 +142,21 @@ static unsigned int ar933x_uart_tx_empty(struct uart_port *port)
static unsigned int ar933x_uart_get_mctrl(struct uart_port *port)
{
return TIOCM_CAR;
struct ar933x_uart_port *up =
container_of(port, struct ar933x_uart_port, port);
int ret = TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
mctrl_gpio_get(up->gpios, &ret);
return ret;
}
static void ar933x_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
struct ar933x_uart_port *up =
container_of(port, struct ar933x_uart_port, port);
mctrl_gpio_set(up->gpios, mctrl);
}
static void ar933x_uart_start_tx(struct uart_port *port)
@ -140,6 +167,37 @@ static void ar933x_uart_start_tx(struct uart_port *port)
ar933x_uart_start_tx_interrupt(up);
}
static void ar933x_uart_wait_tx_complete(struct ar933x_uart_port *up)
{
unsigned int status;
unsigned int timeout = 60000;
/* Wait up to 60ms for the character(s) to be sent. */
do {
status = ar933x_uart_read(up, AR933X_UART_CS_REG);
if (--timeout == 0)
break;
udelay(1);
} while (status & AR933X_UART_CS_TX_BUSY);
if (timeout == 0)
dev_err(up->port.dev, "waiting for TX timed out\n");
}
static void ar933x_uart_rx_flush(struct ar933x_uart_port *up)
{
unsigned int status;
/* clear RX_VALID interrupt */
ar933x_uart_write(up, AR933X_UART_INT_REG, AR933X_UART_INT_RX_VALID);
/* remove characters from the RX FIFO */
do {
ar933x_uart_write(up, AR933X_UART_DATA_REG, AR933X_UART_DATA_RX_CSR);
status = ar933x_uart_read(up, AR933X_UART_DATA_REG);
} while (status & AR933X_UART_DATA_RX_CSR);
}
static void ar933x_uart_stop_tx(struct uart_port *port)
{
struct ar933x_uart_port *up =
@ -153,8 +211,7 @@ static void ar933x_uart_stop_rx(struct uart_port *port)
struct ar933x_uart_port *up =
container_of(port, struct ar933x_uart_port, port);
up->ier &= ~AR933X_UART_INT_RX_VALID;
ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
ar933x_uart_stop_rx_interrupt(up);
}
static void ar933x_uart_break_ctl(struct uart_port *port, int break_state)
@ -336,11 +393,20 @@ static void ar933x_uart_rx_chars(struct ar933x_uart_port *up)
static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)
{
struct circ_buf *xmit = &up->port.state->xmit;
struct serial_rs485 *rs485conf = &up->port.rs485;
int count;
bool half_duplex_send = false;
if (uart_tx_stopped(&up->port))
return;
if ((rs485conf->flags & SER_RS485_ENABLED) &&
(up->port.x_char || !uart_circ_empty(xmit))) {
ar933x_uart_stop_rx_interrupt(up);
gpiod_set_value(up->rts_gpiod, !!(rs485conf->flags & SER_RS485_RTS_ON_SEND));
half_duplex_send = true;
}
count = up->port.fifosize;
do {
unsigned int rdata;
@ -368,8 +434,14 @@ static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(&up->port);
if (!uart_circ_empty(xmit))
if (!uart_circ_empty(xmit)) {
ar933x_uart_start_tx_interrupt(up);
} else if (half_duplex_send) {
ar933x_uart_wait_tx_complete(up);
ar933x_uart_rx_flush(up);
ar933x_uart_start_rx_interrupt(up);
gpiod_set_value(up->rts_gpiod, !!(rs485conf->flags & SER_RS485_RTS_AFTER_SEND));
}
}
static irqreturn_t ar933x_uart_interrupt(int irq, void *dev_id)
@ -427,8 +499,7 @@ static int ar933x_uart_startup(struct uart_port *port)
AR933X_UART_CS_TX_READY_ORIDE | AR933X_UART_CS_RX_READY_ORIDE);
/* Enable RX interrupts */
up->ier = AR933X_UART_INT_RX_VALID;
ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
ar933x_uart_start_rx_interrupt(up);
spin_unlock_irqrestore(&up->port.lock, flags);
@ -511,6 +582,21 @@ static const struct uart_ops ar933x_uart_ops = {
.verify_port = ar933x_uart_verify_port,
};
static int ar933x_config_rs485(struct uart_port *port,
struct serial_rs485 *rs485conf)
{
struct ar933x_uart_port *up =
container_of(port, struct ar933x_uart_port, port);
if ((rs485conf->flags & SER_RS485_ENABLED) &&
!up->rts_gpiod) {
dev_err(port->dev, "RS485 needs rts-gpio\n");
return 1;
}
port->rs485 = *rs485conf;
return 0;
}
#ifdef CONFIG_SERIAL_AR933X_CONSOLE
static struct ar933x_uart_port *
ar933x_console_ports[CONFIG_SERIAL_AR933X_NR_UARTS];
@ -680,6 +766,8 @@ static int ar933x_uart_probe(struct platform_device *pdev)
goto err_disable_clk;
}
uart_get_rs485_mode(&pdev->dev, &port->rs485);
port->mapbase = mem_res->start;
port->line = id;
port->irq = irq_res->start;
@ -690,6 +778,7 @@ static int ar933x_uart_probe(struct platform_device *pdev)
port->regshift = 2;
port->fifosize = AR933X_UART_FIFO_SIZE;
port->ops = &ar933x_uart_ops;
port->rs485_config = ar933x_config_rs485;
baud = ar933x_uart_get_baud(port->uartclk, AR933X_UART_MAX_SCALE, 1);
up->min_baud = max_t(unsigned int, baud, AR933X_UART_MIN_BAUD);
@ -697,6 +786,18 @@ static int ar933x_uart_probe(struct platform_device *pdev)
baud = ar933x_uart_get_baud(port->uartclk, 0, AR933X_UART_MAX_STEP);
up->max_baud = min_t(unsigned int, baud, AR933X_UART_MAX_BAUD);
up->gpios = mctrl_gpio_init(port, 0);
if (IS_ERR(up->gpios) && PTR_ERR(up->gpios) != -ENOSYS)
return PTR_ERR(up->gpios);
up->rts_gpiod = mctrl_gpio_to_gpiod(up->gpios, UART_GPIO_RTS);
if ((port->rs485.flags & SER_RS485_ENABLED) &&
!up->rts_gpiod) {
dev_err(&pdev->dev, "lacking rts-gpio, disabling RS485\n");
port->rs485.flags &= ~SER_RS485_ENABLED;
}
#ifdef CONFIG_SERIAL_AR933X_CONSOLE
ar933x_console_ports[up->port.line] = up;
#endif