Commit eb56b7ed authored Oct 11, 2013 by Huang Shijie Committed by Greg Kroah-Hartman Oct 16, 2013

serial: imx: implement the flush_buffer hook



The current driver does not implement the flush_buffer hook for
uart_ops. When we enable the DMA for the driver, and test it with Bluetooth,
we may meet the following bug for TX:

    [1] User application may call the flush operation at any time.
        The uart_flush_buffer() calls the uart_circ_clear() to set
        the xmit->head and xmit->tail with 0.

    [2] The TX DMA callback can be called at any time too.
        The dma_tx_call() will update the xmit->tail.

    If [2] occurs just after the [1], we will get the wrong xmit->tail.

This patch implements the flush_buffer hook to fix this issue.

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

parent fa2b5ea0

drivers/tty/serial/imx.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -1303,6 +1303,16 @@ static void imx_shutdown(struct uart_port *port)
		clk_disable_unprepare(sport->clk_ipg);
		}

		static void imx_flush_buffer(struct uart_port *port)
		{
		struct imx_port sport = (struct imx_port )port;

		if (sport->dma_is_enabled) {
		sport->tx_bytes = 0;
		dmaengine_terminate_all(sport->dma_chan_tx);
		}
		}

		static void
		imx_set_termios(struct uart_port port, struct ktermios termios,
		struct ktermios *old)
		@@ -1623,6 +1633,7 @@ static struct uart_ops imx_pops = {
		.break_ctl = imx_break_ctl,
		.startup = imx_startup,
		.shutdown = imx_shutdown,
		.flush_buffer = imx_flush_buffer,
		.set_termios = imx_set_termios,
		.type = imx_type,
		.release_port = imx_release_port,