From: Huang Shijie Date: Fri, 11 Oct 2013 10:30:59 +0000 (+0800) Subject: serial: imx: check the DMA for imx_tx_empty X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=1ce43e58d4d57acc9782d97270ec70a91a177abc;p=linux-beck.git 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 Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 708ba899258d..c6c3b160dac7 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -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; } /*