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Commit 6e0a5de2 authored by Rafael Gago's avatar Rafael Gago Committed by Greg Kroah-Hartman
Browse files

serial: 8250: Use hrtimers for rs485 delays 



Previously the timers where based on the classic timers, giving a too
coarse resolution on systems with configs of less than 1000 HZ.

This patch changes the rs485 timers to hrtimers.

Signed-off-by: default avatarRafael Gago Castano <rgc@hms.se>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent a6845e1e

drivers/tty/serial/8250/8250_port.c

+40 −23
Original line number Diff line number Diff line
@@ -37,7 +37,7 @@ 
#include <linux/slab.h>

#include <linux/uaccess.h>

#include <linux/pm_runtime.h>

#include <linux/timer.h>

#include <linux/ktime.h>



#include <asm/io.h>

#include <asm/irq.h>
@@ -553,8 +553,8 @@ static inline void serial8250_em485_rts_after_send(struct uart_8250_port *p) 
	serial8250_out_MCR(p, mcr);

}



static void serial8250_em485_handle_start_tx(unsigned long arg);

static void serial8250_em485_handle_stop_tx(unsigned long arg);

static enum hrtimer_restart serial8250_em485_handle_start_tx(struct hrtimer *t);

static enum hrtimer_restart serial8250_em485_handle_stop_tx(struct hrtimer *t);



void serial8250_clear_and_reinit_fifos(struct uart_8250_port *p)

{
@@ -609,12 +609,14 @@ int serial8250_em485_init(struct uart_8250_port *p) 
	if (!p->em485)

		return -ENOMEM;



	setup_timer(&p->em485->stop_tx_timer,

		serial8250_em485_handle_stop_tx, (unsigned long)p);

	setup_timer(&p->em485->start_tx_timer,

		serial8250_em485_handle_start_tx, (unsigned long)p);

	hrtimer_init(&p->em485->stop_tx_timer, CLOCK_MONOTONIC,

		     HRTIMER_MODE_REL);

	hrtimer_init(&p->em485->start_tx_timer, CLOCK_MONOTONIC,

		     HRTIMER_MODE_REL);

	p->em485->stop_tx_timer.function = &serial8250_em485_handle_stop_tx;

	p->em485->start_tx_timer.function = &serial8250_em485_handle_start_tx;

	p->em485->port = p;

	p->em485->active_timer = NULL;



	serial8250_em485_rts_after_send(p);



	return 0;
@@ -639,8 +641,8 @@ void serial8250_em485_destroy(struct uart_8250_port *p) 
	if (!p->em485)

		return;



	del_timer(&p->em485->start_tx_timer);

	del_timer(&p->em485->stop_tx_timer);

	hrtimer_cancel(&p->em485->start_tx_timer);

	hrtimer_cancel(&p->em485->stop_tx_timer);



	kfree(p->em485);

	p->em485 = NULL;
@@ -1435,12 +1437,13 @@ static void __do_stop_tx_rs485(struct uart_8250_port *p) 
		serial_port_out(&p->port, UART_IER, p->ier);

	}

}



static void serial8250_em485_handle_stop_tx(unsigned long arg)

static enum hrtimer_restart serial8250_em485_handle_stop_tx(struct hrtimer *t)

{

	struct uart_8250_port *p = (struct uart_8250_port *)arg;

	struct uart_8250_em485 *em485 = p->em485;

	struct uart_8250_em485 *em485;

	struct uart_8250_port *p;

	unsigned long flags;

	em485 = container_of(t, struct uart_8250_em485, stop_tx_timer);

	p = em485->port;



	serial8250_rpm_get(p);

	spin_lock_irqsave(&p->port.lock, flags);
@@ -1451,6 +1454,16 @@ static void serial8250_em485_handle_stop_tx(unsigned long arg) 
	}

	spin_unlock_irqrestore(&p->port.lock, flags);

	serial8250_rpm_put(p);

	return HRTIMER_NORESTART;

}



static void start_hrtimer_ms(struct hrtimer *hrt, unsigned long msec)

{

	long sec = msec / 1000;

	long nsec = (msec % 1000) * 1000000;

	ktime_t t = ktime_set(sec, nsec);



	hrtimer_start(hrt, t, HRTIMER_MODE_REL);

}



static void __stop_tx_rs485(struct uart_8250_port *p)
@@ -1463,8 +1476,8 @@ static void __stop_tx_rs485(struct uart_8250_port *p) 
	 */

	if (p->port.rs485.delay_rts_after_send > 0) {

		em485->active_timer = &em485->stop_tx_timer;

		mod_timer(&em485->stop_tx_timer, jiffies +

			p->port.rs485.delay_rts_after_send * HZ / 1000);

		start_hrtimer_ms(&em485->stop_tx_timer,

				   p->port.rs485.delay_rts_after_send);

	} else {

		__do_stop_tx_rs485(p);

	}
@@ -1494,8 +1507,8 @@ static inline void __stop_tx(struct uart_8250_port *p) 
		if ((lsr & BOTH_EMPTY) != BOTH_EMPTY)

			return;



		del_timer(&em485->start_tx_timer);

		em485->active_timer = NULL;

		hrtimer_cancel(&em485->start_tx_timer);



		__stop_tx_rs485(p);

	}
@@ -1558,8 +1571,9 @@ static inline void start_tx_rs485(struct uart_port *port) 
	if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX))

		serial8250_stop_rx(&up->port);



	del_timer(&em485->stop_tx_timer);

	em485->active_timer = NULL;

	if (hrtimer_is_queued(&em485->stop_tx_timer))

		hrtimer_cancel(&em485->stop_tx_timer);



	mcr = serial8250_in_MCR(up);

	if (!!(up->port.rs485.flags & SER_RS485_RTS_ON_SEND) !=
@@ -1572,8 +1586,8 @@ static inline void start_tx_rs485(struct uart_port *port) 


		if (up->port.rs485.delay_rts_before_send > 0) {

			em485->active_timer = &em485->start_tx_timer;

			mod_timer(&em485->start_tx_timer, jiffies +

				up->port.rs485.delay_rts_before_send * HZ / 1000);

			start_hrtimer_ms(&em485->start_tx_timer,

					 up->port.rs485.delay_rts_before_send);

			return;

		}

	}
@@ -1581,11 +1595,13 @@ static inline void start_tx_rs485(struct uart_port *port) 
	__start_tx(port);

}



static void serial8250_em485_handle_start_tx(unsigned long arg)

static enum hrtimer_restart serial8250_em485_handle_start_tx(struct hrtimer *t)

{

	struct uart_8250_port *p = (struct uart_8250_port *)arg;

	struct uart_8250_em485 *em485 = p->em485;

	struct uart_8250_em485 *em485;

	struct uart_8250_port *p;

	unsigned long flags;

	em485 = container_of(t, struct uart_8250_em485, start_tx_timer);

	p = em485->port;



	spin_lock_irqsave(&p->port.lock, flags);

	if (em485 &&
@@ -1594,6 +1610,7 @@ static void serial8250_em485_handle_start_tx(unsigned long arg) 
		em485->active_timer = NULL;

	}

	spin_unlock_irqrestore(&p->port.lock, flags);

	return HRTIMER_NORESTART;

}



static void serial8250_start_tx(struct uart_port *port)

include/linux/serial_8250.h

+4 −3
Original line number Diff line number Diff line
@@ -80,9 +80,10 @@ struct uart_8250_ops { 
};



struct uart_8250_em485 {

	struct timer_list	start_tx_timer; /* "rs485 start tx" timer */

	struct timer_list	stop_tx_timer;  /* "rs485 stop tx" timer */

	struct timer_list	*active_timer;  /* pointer to active timer */

	struct hrtimer		start_tx_timer; /* "rs485 start tx" timer */

	struct hrtimer		stop_tx_timer;  /* "rs485 stop tx" timer */

	struct hrtimer		*active_timer;  /* pointer to active timer */

	struct uart_8250_port	*port;          /* for hrtimer callbacks */

};



/*