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Message-ID: <20200221212331.GA21467@makrotopia.org>
Date: Fri, 21 Feb 2020 22:23:31 +0100
From: Daniel Golle <daniel@...rotopia.org>
To: linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jslaby@...e.com>,
Petr Štetiar <ynezz@...e.cz>,
Chuanhong Guo <gch981213@...il.com>,
Piotr Dymacz <pepe2k@...il.com>
Subject: [PATCH v2] serial: ar933x_uart: add RS485 support
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@...rotopia.org>
---
v2: use bool to indicate ongoing half-duplex send, use it afterwards
to decide whether we've just been in a send operation.
drivers/tty/serial/Kconfig | 1 +
drivers/tty/serial/ar933x_uart.c | 113 +++++++++++++++++++++++++++++--
2 files changed, 108 insertions(+), 6 deletions(-)
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 52eaac21ff9f..b675924138e0 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1279,6 +1279,7 @@ 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.
diff --git a/drivers/tty/serial/ar933x_uart.c b/drivers/tty/serial/ar933x_uart.c
index ea12f10610b6..7e7f1398019f 100644
--- a/drivers/tty/serial/ar933x_uart.c
+++ b/drivers/tty/serial/ar933x_uart.c
@@ -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
--
2.25.1
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