serial: sirf: fix system hung on console log output

A corner case exists in the current driver. if an app opens the console
device, and before writing to console device, and there are huge kernel
ogs to print out, system will hang on
sirfsoc_uart_console_putchar:
while (rd_regl(port, ureg->sirfsoc_tx_fifo_status) &
	ufifo_st->ff_full(port->line))
	cpu_relax();
as in sirfsoc_uart_startup(), the driver assigns tx_fifo_op to 0 will stop
TX FIFO, this loop will be endless.

Signed-off-by: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sirfsoc_uart.c b/drivers/tty/serial/sirfsoc_uart.c
index 8d759629ffb0238bbfd455b4ccc8235787623cc5..6b1c92c1c27f5efd32518088ccb8b7d22458562a 100644 (file)
--- a/drivers/tty/serial/sirfsoc_uart.c
+++ b/drivers/tty/serial/sirfsoc_uart.c
@@ -272,6 +272,7 @@ static void sirfsoc_uart_start_tx(struct uart_port *port)
                if (sirfport->uart_reg->uart_type == SIRF_USP_UART)
                        wr_regl(port, ureg->sirfsoc_tx_rx_en, rd_regl(port,
                                ureg->sirfsoc_tx_rx_en) | SIRFUART_TX_EN);
+               wr_regl(port, ureg->sirfsoc_tx_fifo_op, SIRFUART_FIFO_STOP);
                sirfsoc_uart_pio_tx_chars(sirfport, port->fifosize);
                wr_regl(port, ureg->sirfsoc_tx_fifo_op, SIRFUART_FIFO_START);
                if (!sirfport->is_atlas7)
@@ -1117,7 +1118,6 @@ static int sirfsoc_uart_startup(struct uart_port *port)
                        SIRFSOC_USP_ENDIAN_CTRL_LSBF |
                        SIRFSOC_USP_EN);
        wr_regl(port, ureg->sirfsoc_tx_fifo_op, SIRFUART_FIFO_RESET);
-       wr_regl(port, ureg->sirfsoc_tx_fifo_op, 0);
        wr_regl(port, ureg->sirfsoc_rx_fifo_op, SIRFUART_FIFO_RESET);
        wr_regl(port, ureg->sirfsoc_rx_fifo_op, 0);
        wr_regl(port, ureg->sirfsoc_tx_fifo_ctrl, SIRFUART_FIFO_THD(port));