From: Peter Hurley Date: Mon, 2 Feb 2015 20:47:07 +0000 (-0500) Subject: serial: 8250: Fix UART_BUG_TXEN workaround X-Git-Tag: v4.0-rc1~81^2 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=c09babfab7ae8c7d79a5dce9d866fbb28b82dde4;p=linux.git serial: 8250: Fix UART_BUG_TXEN workaround UARTs which do not trigger THRE interrupt if the fifo is already empty when the interrupt is enabled need tx primed manually. These UARTs are identified by the UART_BUG_TXEN flag to enable the required workaround. However, the current workaround is broken; if the fifo is already empty but the shifter is still transmitting, then serial8250_tx_chars() will not be called but no further THRE interrupt will occur, and tx will stall. The appropriate check is for fifo empty (THRE), not transmitter empty (TEMT). Signed-off-by: Dick Hollenbeck [pjh: rewrote commit log] Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 46ae9fda68b6..e3b9570a1eff 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -1388,7 +1388,7 @@ static void serial8250_start_tx(struct uart_port *port) unsigned char lsr; lsr = serial_in(up, UART_LSR); up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS; - if (lsr & UART_LSR_TEMT) + if (lsr & UART_LSR_THRE) serial8250_tx_chars(up); } }