Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753969AbbLEK41 (ORCPT ); Sat, 5 Dec 2015 05:56:27 -0500 Received: from mail-lb0-f176.google.com ([209.85.217.176]:35709 "EHLO mail-lb0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753388AbbLEK4Y (ORCPT ); Sat, 5 Dec 2015 05:56:24 -0500 From: "Matwey V. Kornilov" To: gregkh@linuxfoundation.org, jslaby@suse.com, peter@hurleysoftware.com, andy.shevchenko@gmail.com, gnomes@lxorguk.ukuu.org.uk Cc: "Matwey V. Kornilov" , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org Subject: [PATCH v4 2/3] tty: Add software emulated RS485 support for 8250 Date: Sat, 5 Dec 2015 13:54:50 +0300 Message-Id: <1449312891-1846-3-git-send-email-matwey@sai.msu.ru> X-Mailer: git-send-email 2.6.3 In-Reply-To: <1449312891-1846-1-git-send-email-matwey@sai.msu.ru> References: <1449312891-1846-1-git-send-email-matwey@sai.msu.ru> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8662 Lines: 285 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. Note that before calling serial8250_em485_init the caller has to ensure that UART will interrupt when shift register empty. Otherwise, emultaion cannot be used. Both serial8250_em485_init and serial8250_em485_destroy are idempotent functions. Signed-off-by: Matwey V. Kornilov --- drivers/tty/serial/8250/8250.h | 6 ++ drivers/tty/serial/8250/8250_port.c | 161 +++++++++++++++++++++++++++++++++++- include/linux/serial_8250.h | 7 ++ 3 files changed, 170 insertions(+), 4 deletions(-) diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h index d54dcd8..a3816c6 100644 --- a/drivers/tty/serial/8250/8250.h +++ b/drivers/tty/serial/8250/8250.h @@ -117,6 +117,12 @@ static inline void serial_dl_write(struct uart_8250_port *up, int value) struct uart_8250_port *serial8250_get_port(int line); void serial8250_rpm_get(struct uart_8250_port *p); void serial8250_rpm_put(struct uart_8250_port *p); +int serial8250_em485_init(struct uart_8250_port *p); +void serial8250_em485_destroy(struct uart_8250_port *p); +static inline bool serial8250_em485_enabled(struct uart_8250_port *p) +{ + return p->rs485_emul && (p->port.rs485.flags & SER_RS485_ENABLED); +} #if defined(__alpha__) && !defined(CONFIG_PCI) /* diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 8ad0b2d..394d0d2 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -37,6 +37,7 @@ #include #include #include +#include #include #include @@ -504,6 +505,31 @@ static void serial8250_clear_fifos(struct uart_8250_port *p) } } +static inline void serial8250_em485_rts_on_send(struct uart_8250_port *p) +{ + unsigned char mcr = serial_in(p, UART_MCR); + + if (p->port.rs485.flags & SER_RS485_RTS_ON_SEND) + mcr |= UART_MCR_RTS; + else + mcr &= ~UART_MCR_RTS; + serial_out(p, UART_MCR, mcr); +} + +static inline void serial8250_em485_rts_after_send(struct uart_8250_port *p) +{ + unsigned char mcr = serial_in(p, UART_MCR); + + if (p->port.rs485.flags & SER_RS485_RTS_AFTER_SEND) + mcr |= UART_MCR_RTS; + else + mcr &= ~UART_MCR_RTS; + serial_out(p, UART_MCR, mcr); +} + +static void serial8250_em485_handle_start_tx(unsigned long arg); +static void serial8250_em485_handle_stop_tx(unsigned long arg); + void serial8250_clear_and_reinit_fifos(struct uart_8250_port *p) { serial8250_clear_fifos(p); @@ -528,6 +554,42 @@ void serial8250_rpm_put(struct uart_8250_port *p) } EXPORT_SYMBOL_GPL(serial8250_rpm_put); +int serial8250_em485_init(struct uart_8250_port *p) +{ + if (p->rs485_emul != NULL) + return 0; + + p->rs485_emul = kmalloc(sizeof(struct uart_8250_rs485_emul), GFP_KERNEL); + if (p->rs485_emul == NULL) + return -ENOMEM; + + init_timer(&p->rs485_emul->stop_tx_timer); + p->rs485_emul->stop_tx_timer.function = serial8250_em485_handle_stop_tx; + p->rs485_emul->stop_tx_timer.data = (unsigned long)p; + p->rs485_emul->stop_tx_timer.flags |= TIMER_IRQSAFE; + init_timer(&p->rs485_emul->start_tx_timer); + p->rs485_emul->start_tx_timer.function = serial8250_em485_handle_start_tx; + p->rs485_emul->start_tx_timer.data = (unsigned long)p; + p->rs485_emul->start_tx_timer.flags |= TIMER_IRQSAFE; + + serial8250_em485_rts_after_send(p); + + return 0; +} +EXPORT_SYMBOL_GPL(serial8250_em485_init); +void serial8250_em485_destroy(struct uart_8250_port *p) +{ + if (p->rs485_emul == NULL) + return; + + del_timer_sync(&p->rs485_emul->start_tx_timer); + del_timer_sync(&p->rs485_emul->stop_tx_timer); + + kfree(p->rs485_emul); + p->rs485_emul = NULL; +} +EXPORT_SYMBOL_GPL(serial8250_em485_destroy); + /* * These two wrappers ensure that enable_runtime_pm_tx() can be called more than * once and disable_runtime_pm_tx() will still disable RPM because the fifo is @@ -1293,7 +1355,61 @@ static void serial8250_stop_rx(struct uart_port *port) serial8250_rpm_put(up); } -static inline void __stop_tx(struct uart_8250_port *p) +static __u32 __start_tx_rs485(struct uart_8250_port *p) +{ + if (!serial8250_em485_enabled(p)) + return 0; + + if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) + serial8250_stop_rx(&p->port); + + del_timer_sync(&p->rs485_emul->stop_tx_timer); + + if (!!(p->port.rs485.flags & SER_RS485_RTS_ON_SEND) != !!(serial_in(p, UART_MCR) & UART_MCR_RTS)) { + serial8250_em485_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) +{ + if (!serial8250_em485_enabled(p)) + return; + + serial8250_em485_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_em485_handle_stop_tx(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 (!serial8250_em485_enabled(p)) + return; + + del_timer_sync(&p->rs485_emul->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_emul->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; @@ -1302,6 +1418,21 @@ static inline void __stop_tx(struct uart_8250_port *p) } } +static inline void __stop_tx(struct uart_8250_port *p) +{ + if (serial8250_em485_enabled(p)) { + unsigned char lsr = serial_in(p, UART_LSR); + /* To provide required timeing and allow FIFO transfer, + * __stop_tx_rs485 must be called only when both FIFO and shift register + * are empty. It is for device driver to enable interrupt on TEMT. + */ + if (!((lsr & UART_LSR_TEMT) && (lsr & UART_LSR_THRE))) + return; + } + __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); @@ -1319,12 +1450,10 @@ 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; @@ -1350,6 +1479,30 @@ static void serial8250_start_tx(struct uart_port *port) } } +static void serial8250_em485_handle_start_tx(unsigned long arg) +{ + struct uart_8250_port *p = (struct uart_8250_port *)arg; + + __start_tx(&p->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 (up->rs485_emul && timer_pending(&up->rs485_emul->start_tx_timer)) + return; + + if (up->rs485_emul && (delay = __start_tx_rs485(up))) { + mod_timer(&up->rs485_emul->start_tx_timer, jiffies + delay * HZ / 1000); + } else { + __start_tx(port); + } +} + static void serial8250_throttle(struct uart_port *port) { port->throttle(port); diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h index faa0e03..99e59fc 100644 --- a/include/linux/serial_8250.h +++ b/include/linux/serial_8250.h @@ -76,6 +76,11 @@ struct uart_8250_ops { void (*release_irq)(struct uart_8250_port *); }; +struct uart_8250_rs485_emul { + struct timer_list start_tx_timer; /* "rs485 start tx" timer */ + struct timer_list stop_tx_timer; /* "rs485 stop tx" timer */ +}; + /* * This should be used by drivers which want to register * their own 8250 ports without registering their own @@ -122,6 +127,8 @@ struct uart_8250_port { /* 8250 specific callbacks */ int (*dl_read)(struct uart_8250_port *); void (*dl_write)(struct uart_8250_port *, int); + + struct uart_8250_rs485_emul *rs485_emul; }; static inline struct uart_8250_port *up_to_u8250p(struct uart_port *up) -- 2.6.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/