Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754415AbbLTQlX (ORCPT ); Sun, 20 Dec 2015 11:41:23 -0500 Received: from mail-yk0-f171.google.com ([209.85.160.171]:34259 "EHLO mail-yk0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753219AbbLTQlU convert rfc822-to-8bit (ORCPT ); Sun, 20 Dec 2015 11:41:20 -0500 MIME-Version: 1.0 In-Reply-To: <1449919416-1980-3-git-send-email-matwey@sai.msu.ru> References: <1449919416-1980-1-git-send-email-matwey@sai.msu.ru> <1449919416-1980-3-git-send-email-matwey@sai.msu.ru> Date: Sun, 20 Dec 2015 18:41:19 +0200 Message-ID: Subject: Re: [PATCH v5 2/3] tty: Add software emulated RS485 support for 8250 From: Andy Shevchenko To: "Matwey V. Kornilov" Cc: Greg Kroah-Hartman , Jiri Slaby , Peter Hurley , One Thousand Gnomes , "linux-kernel@vger.kernel.org" , "linux-serial@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10394 Lines: 301 On Sat, Dec 12, 2015 at 1:23 PM, Matwey V. Kornilov wrote: > 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. Just nitpick suggesting to rename both struct and field: struct uart_8250_rs485em *rs485em; (might be 'sw' suffix as well, which I like more — rs485sw) and corresponding local variables if any. > > 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 > -- With Best Regards, Andy Shevchenko -- 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/