Implementation of software emulation of RS485 direction handling is based on omap-serial driver. Before and after transmission RTS is set to the appropriate value.
Signed-off-by: Matwey V. Kornilov <[email protected]> --- drivers/tty/serial/8250/8250_port.c | 152 ++++++++++++++++++++++++++++++++++-- include/linux/serial_8250.h | 2 + 2 files changed, 148 insertions(+), 6 deletions(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 3f6d8a2..b863a12 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -37,6 +37,7 @@ #include <linux/slab.h> #include <linux/uaccess.h> #include <linux/pm_runtime.h> +#include <linux/timer.h> #include <asm/io.h> #include <asm/irq.h> @@ -1299,7 +1300,75 @@ static void serial8250_stop_rx(struct uart_port *port) serial8250_rpm_put(up); } -static inline void __stop_tx(struct uart_8250_port *p) +static inline void serial8250_rs485_set_rts_on_send(struct uart_8250_port *p) +{ + if (p->port.rs485.flags & SER_RS485_RTS_ON_SEND) + p->mcr |= UART_MCR_RTS; + else + p->mcr &= ~UART_MCR_RTS; + serial_out(p, UART_MCR, p->mcr); +} + +static inline void serial8250_rs485_set_rts_after_send(struct uart_8250_port *p) +{ + if (p->port.rs485.flags & SER_RS485_RTS_AFTER_SEND) + p->mcr |= UART_MCR_RTS; + else + p->mcr &= ~UART_MCR_RTS; + serial_out(p, UART_MCR, p->mcr); +} + +static __u32 serial8250_rs485_start_tx(struct uart_8250_port *p) +{ + if (p->capabilities & UART_CAP_HW485 || !(p->port.rs485.flags & SER_RS485_ENABLED)) + return 0; + + if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) + serial8250_stop_rx(&p->port); + + del_timer_sync(&p->rs485_stop_tx_timer); + + if (!!(p->port.rs485.flags & SER_RS485_RTS_ON_SEND) != !!(p->mcr & UART_MCR_RTS)) { + serial8250_rs485_set_rts_on_send(p); + return p->port.rs485.delay_rts_before_send; + } + + return 0; +} + +static inline void __do_stop_tx_rs485(struct uart_8250_port *p) +{ + serial8250_rs485_set_rts_after_send(p); + /* + * Empty the RX FIFO, we are not interested in anything + * received during the half-duplex transmission. + */ + if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) + serial8250_clear_fifos(p); +} + +static void serial8250_handle_rs485_stop_tx_timer(unsigned long arg) +{ + struct uart_8250_port *p = (struct uart_8250_port*)arg; + __do_stop_tx_rs485(p); +} + +static inline void __stop_tx_rs485(struct uart_8250_port *p) +{ + if (p->capabilities & UART_CAP_HW485 || !(p->port.rs485.flags & SER_RS485_ENABLED)) + return; + + del_timer_sync(&p->rs485_start_tx_timer); + + /* __do_stop_tx_rs485 is going to set RTS according to config AND flush RX FIFO if required */ + if (p->port.rs485.delay_rts_after_send > 0) { + mod_timer(&p->rs485_stop_tx_timer, jiffies + p->port.rs485.delay_rts_after_send * HZ / 1000); + } else { + __do_stop_tx_rs485(p); + } +} + +static inline void __do_stop_tx(struct uart_8250_port *p) { if (p->ier & UART_IER_THRI) { p->ier &= ~UART_IER_THRI; @@ -1308,6 +1377,12 @@ static inline void __stop_tx(struct uart_8250_port *p) } } +static inline void __stop_tx(struct uart_8250_port *p) +{ + __do_stop_tx(p); + __stop_tx_rs485(p); +} + static void serial8250_stop_tx(struct uart_port *port) { struct uart_8250_port *up = up_to_u8250p(port); @@ -1325,12 +1400,10 @@ static void serial8250_stop_tx(struct uart_port *port) serial8250_rpm_put(up); } -static void serial8250_start_tx(struct uart_port *port) +static inline void __start_tx(struct uart_port* port) { struct uart_8250_port *up = up_to_u8250p(port); - serial8250_rpm_get_tx(up); - if (up->dma && !up->dma->tx_dma(up)) return; @@ -1356,6 +1429,29 @@ static void serial8250_start_tx(struct uart_port *port) } } +static void serial8250_handle_rs485_start_tx_timer(unsigned long arg) +{ + struct uart_port* port = (struct uart_port*)arg; + __start_tx(port); +} + +static void serial8250_start_tx(struct uart_port *port) +{ + struct uart_8250_port *up = up_to_u8250p(port); + __u32 delay; + + serial8250_rpm_get_tx(up); + + if (timer_pending(&up->rs485_start_tx_timer)) + return; + + if ((delay = serial8250_rs485_start_tx(up))) { + mod_timer(&up->rs485_start_tx_timer, jiffies + delay * HZ / 1000); + } else { + __start_tx(port); + } +} + static void serial8250_throttle(struct uart_port *port) { port->throttle(port); @@ -1806,6 +1902,16 @@ static void serial8250_put_poll_char(struct uart_port *port, #endif /* CONFIG_CONSOLE_POLL */ +static inline void serial8250_startup_rs485(struct uart_port *port) +{ + struct uart_8250_port *up = up_to_u8250p(port); + + if (up->capabilities & UART_CAP_HW485 || !(up->port.rs485.flags & SER_RS485_ENABLED)) + return; + + serial8250_rs485_set_rts_after_send(up); +} + int serial8250_do_startup(struct uart_port *port) { struct uart_8250_port *up = up_to_u8250p(port); @@ -2044,6 +2150,8 @@ dont_test_tx_en: inb_p(icp); } retval = 0; + + serial8250_startup_rs485(port); out: serial8250_rpm_put(up); return retval; @@ -2057,12 +2165,24 @@ static int serial8250_startup(struct uart_port *port) return serial8250_do_startup(port); } +static inline void serial8250_shutdown_rs485(struct uart_port *port) +{ + struct uart_8250_port *up = up_to_u8250p(port); + + if (up->capabilities & UART_CAP_HW485 || !(up->port.rs485.flags & SER_RS485_ENABLED)) + return; + + del_timer_sync(&up->rs485_start_tx_timer); + del_timer_sync(&up->rs485_stop_tx_timer); +} + void serial8250_do_shutdown(struct uart_port *port) { struct uart_8250_port *up = up_to_u8250p(port); unsigned long flags; serial8250_rpm_get(up); + serial8250_shutdown_rs485(port); /* * Disable interrupts from this port */ @@ -2735,11 +2855,23 @@ serial8250_type(struct uart_port *port) return uart_config[type].name; } -static int serial8250_rs485_config(struct uart_port *port, - struct serial_rs485 *rs485) +static int serial8250_rs485_config(struct uart_port *port, struct serial_rs485 *rs485) { + bool need_startup = false; + + if (!(port->rs485.flags & SER_RS485_ENABLED) && (rs485->flags & SER_RS485_ENABLED)) { + need_startup = true; + } + if ((port->rs485.flags & SER_RS485_ENABLED) && !(rs485->flags & SER_RS485_ENABLED)) { + serial8250_shutdown_rs485(port); + } + port->rs485 = *rs485; port->rs485.flags |= SER_RS485_SOFTWARE; + + if (need_startup) + serial8250_startup_rs485(port); + return 0; } @@ -2807,6 +2939,14 @@ void serial8250_set_defaults(struct uart_8250_port *up) } up->port.rs485_config = serial8250_rs485_config; + init_timer(&up->rs485_stop_tx_timer); + up->rs485_stop_tx_timer.function = serial8250_handle_rs485_stop_tx_timer; + up->rs485_stop_tx_timer.data = (unsigned long)up; + up->rs485_stop_tx_timer.flags |= TIMER_IRQSAFE; + init_timer(&up->rs485_start_tx_timer); + up->rs485_start_tx_timer.function = serial8250_handle_rs485_start_tx_timer; + up->rs485_start_tx_timer.data = (unsigned long)up; + up->rs485_start_tx_timer.flags |= TIMER_IRQSAFE; } EXPORT_SYMBOL_GPL(serial8250_set_defaults); diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h index faa0e03..c4905e7 100644 --- a/include/linux/serial_8250.h +++ b/include/linux/serial_8250.h @@ -86,6 +86,8 @@ struct uart_8250_ops { struct uart_8250_port { struct uart_port port; struct timer_list timer; /* "no irq" timer */ + struct timer_list rs485_start_tx_timer; /* "rs485 start tx" timer */ + struct timer_list rs485_stop_tx_timer; /* "rs485 stop tx" timer */ struct list_head list; /* ports on this IRQ */ unsigned short capabilities; /* port capabilities */ unsigned short bugs; /* port bugs */ -- 2.6.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
