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Commit bb029c67 authored by Paul Fulghum's avatar Paul Fulghum Committed by Linus Torvalds
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synclink_gt: fix transmit DMA stall 



Fix transmit DMA stall when write() called in window after previous
transmit DMA completes but before previous serial transmission completes.

Signed-off-by: default avatarPaul Fulghum <paulkf@microgate.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ddb437b7

drivers/char/synclink_gt.c

+46 −29
Original line number Diff line number Diff line 
/*

 * $Id: synclink_gt.c,v 4.36 2006/08/28 20:47:14 paulkf Exp $

 * $Id: synclink_gt.c,v 4.50 2007/07/25 19:29:25 paulkf Exp $

 *

 * Device driver for Microgate SyncLink GT serial adapters.

 *
@@ -93,7 +93,7 @@ 
 * module identification

 */

static char *driver_name     = "SyncLink GT";

static char *driver_version  = "$Revision: 4.36 $";

static char *driver_version  = "$Revision: 4.50 $";

static char *tty_driver_name = "synclink_gt";

static char *tty_dev_prefix  = "ttySLG";

MODULE_LICENSE("GPL");
@@ -477,6 +477,7 @@ static void tx_set_idle(struct slgt_info *info); 
static unsigned int free_tbuf_count(struct slgt_info *info);

static void reset_tbufs(struct slgt_info *info);

static void tdma_reset(struct slgt_info *info);

static void tdma_start(struct slgt_info *info);

static void tx_load(struct slgt_info *info, const char *buf, unsigned int count);



static void get_signals(struct slgt_info *info);
@@ -904,6 +905,8 @@ static int write(struct tty_struct *tty, 
		spin_lock_irqsave(&info->lock,flags);

		if (!info->tx_active)

		 	tx_start(info);

		else

			tdma_start(info);

		spin_unlock_irqrestore(&info->lock,flags);

 	}
@@ -3871,10 +3874,45 @@ static void tx_start(struct slgt_info *info) 
			slgt_irq_on(info, IRQ_TXUNDER + IRQ_TXIDLE);

			/* clear tx idle and underrun status bits */

			wr_reg16(info, SSR, (unsigned short)(IRQ_TXIDLE + IRQ_TXUNDER));

			if (info->params.mode == MGSL_MODE_HDLC)

				mod_timer(&info->tx_timer, jiffies +

						msecs_to_jiffies(5000));

		} else {

			slgt_irq_off(info, IRQ_TXDATA);

			slgt_irq_on(info, IRQ_TXIDLE);

			/* clear tx idle status bit */

			wr_reg16(info, SSR, IRQ_TXIDLE);

		}

		tdma_start(info);

		info->tx_active = 1;

	}

}



/*

 * start transmit DMA if inactive and there are unsent buffers

 */

static void tdma_start(struct slgt_info *info)

{

	unsigned int i;



			if (!(rd_reg32(info, TDCSR) & BIT0)) {

				/* tx DMA stopped, restart tx DMA */

	if (rd_reg32(info, TDCSR) & BIT0)

		return;



	/* transmit DMA inactive, check for unsent buffers */

	i = info->tbuf_start;

	while (!desc_count(info->tbufs[i])) {

		if (++i == info->tbuf_count)

			i = 0;

		if (i == info->tbuf_current)

			return;

	}

	info->tbuf_start = i;



	/* there are unsent buffers, start transmit DMA */



	/* reset needed if previous error condition */

	tdma_reset(info);



	/* set 1st descriptor address */

	wr_reg32(info, TDDAR, info->tbufs[info->tbuf_start].pdesc);

	switch(info->params.mode) {
@@ -3888,27 +3926,6 @@ static void tx_start(struct slgt_info *info) 
	}

}



			if (info->params.mode == MGSL_MODE_HDLC)

				mod_timer(&info->tx_timer, jiffies +

						msecs_to_jiffies(5000));

		} else {

			tdma_reset(info);

			/* set 1st descriptor address */

			wr_reg32(info, TDDAR, info->tbufs[info->tbuf_start].pdesc);



			slgt_irq_off(info, IRQ_TXDATA);

			slgt_irq_on(info, IRQ_TXIDLE);

			/* clear tx idle status bit */

			wr_reg16(info, SSR, IRQ_TXIDLE);



			/* enable tx DMA */

			wr_reg32(info, TDCSR, BIT0);

		}



		info->tx_active = 1;

	}

}



static void tx_stop(struct slgt_info *info)

{

	unsigned short val;
@@ -4642,8 +4659,8 @@ static unsigned int free_tbuf_count(struct slgt_info *info) 
			i=0;

	} while (i != info->tbuf_current);



	/* last buffer with zero count may be in use, assume it is */

	if (count)

	/* if tx DMA active, last zero count buffer is in use */

	if (count && (rd_reg32(info, TDCSR) & BIT0))

		--count;



	return count;