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Commit 934084a9 authored by Fabio Estevam's avatar Fabio Estevam Committed by Greg Kroah-Hartman
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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: default avatarFabio Estevam <fabio.estevam@freescale.com>
Tested-by: default avatarFugang Duan <B38611@freescale.com>
Acked-by: default avatarJason Liu <r64343@freecale.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent bfc2e07f

drivers/tty/serial/imx.c

+26 −0
Original line number Diff line number Diff line
@@ -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