From 934084a9d2d95d0ce98ae8d1ec3bfe81c95c678c Mon Sep 17 00:00:00 2001 From: Fabio Estevam Date: Tue, 13 Jan 2015 10:00:26 -0200 Subject: serial: imx: Fix imx_flush_buffer() When running an userspace program that does a 'tcflush(fd, TCIOFLUSH)' call we still see the last received character in the URXD register afterwards. Clear UCR2_SRST bit so that the UART FIFO is flushed properly. Since UCR2_SRST also resets some UART registers, we need to save and restore some of them. Signed-off-by: Fabio Estevam Tested-by: Fugang Duan Acked-by: Jason Liu Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/imx.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) (limited to 'drivers/tty') diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 59d9ef10b085..0eb29b1c47ac 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -1320,6 +1320,7 @@ static void imx_flush_buffer(struct uart_port *port) struct imx_port *sport = (struct imx_port *)port; struct scatterlist *sgl = &sport->tx_sgl[0]; unsigned long temp; + int i = 100, ubir, ubmr, ubrc, uts; if (!sport->dma_chan_tx) return; @@ -1334,6 +1335,31 @@ static void imx_flush_buffer(struct uart_port *port) writel(temp, sport->port.membase + UCR1); sport->dma_is_txing = false; } + + /* + * According to the Reference Manual description of the UART SRST bit: + * "Reset the transmit and receive state machines, + * all FIFOs and register USR1, USR2, UBIR, UBMR, UBRC, URXD, UTXD + * and UTS[6-3]". As we don't need to restore the old values from + * USR1, USR2, URXD, UTXD, only save/restore the other four registers + */ + ubir = readl(sport->port.membase + UBIR); + ubmr = readl(sport->port.membase + UBMR); + ubrc = readl(sport->port.membase + UBRC); + uts = readl(sport->port.membase + IMX21_UTS); + + temp = readl(sport->port.membase + UCR2); + temp &= ~UCR2_SRST; + writel(temp, sport->port.membase + UCR2); + + while (!(readl(sport->port.membase + UCR2) & UCR2_SRST) && (--i > 0)) + udelay(1); + + /* Restore the registers */ + writel(ubir, sport->port.membase + UBIR); + writel(ubmr, sport->port.membase + UBMR); + writel(ubrc, sport->port.membase + UBRC); + writel(uts, sport->port.membase + IMX21_UTS); } static void -- cgit v1.2.1