Commit 1ce43e58 authored Oct 11, 2013 by Huang Shijie Committed by Greg Kroah-Hartman Oct 16, 2013

serial: imx: check the DMA for imx_tx_empty



Assume the following situation:

  If the DMA is enabled, and the a TX DMA operation is working,
But we have not issued the TX DMA operation (or we have issued the
TX DMA operation with dma_async_issue_pending(), but the DMA has not
started to move the data from the memory to the TXFIFO).

At this time, we may get the wrong status of the transmitter when we
call the imx_tx_empty. In such situation, only check the USR2_TXDC
does not enough for us.

This patch checks the DMA's situation, and return 0 when the TX DMA is
working.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent eb56b7ed

drivers/tty/serial/imx.c

+8 −1

Original line number	Diff line number	Diff line
		@@ -795,8 +795,15 @@ static irqreturn_t imx_int(int irq, void *dev_id)
		static unsigned int imx_tx_empty(struct uart_port *port)
		{
		struct imx_port sport = (struct imx_port )port;
		unsigned int ret;

		return (readl(sport->port.membase + USR2) & USR2_TXDC) ? TIOCSER_TEMT : 0;
		ret = (readl(sport->port.membase + USR2) & USR2_TXDC) ? TIOCSER_TEMT : 0;

		/* If the TX DMA is working, return 0. */
		if (sport->dma_is_enabled && sport->dma_is_txing)
		ret = 0;

		return ret;
		}

		/*

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