Re: [PATCH v3 5/5] tty: Add software emulated RS485 support for 8250

Andy Shevchenko
2015-11-12T14:48:38Z

On Thu, Nov 12, 2015 at 4:33 PM, Matwey V. Kornilov <matwey@sai.msu.ru> 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.
>

One comment below.

> Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
> ---
> 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;

It seems you are using this pattern three times. What about

static inline bool is_rs485_sw_enabled(struct uart_8250_port *p)
{
return !(p->capabilities & UART_CAP_HW485) &&
(p->port.rs485.flags & SER_RS485_ENABLED);
}

> +
> + 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
>
> --
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--
With Best Regards,
Andy Shevchenko