serial: 8250: Fix UART_BUG_TXEN workaround
authorPeter Hurley <peter@hurleysoftware.com>
Mon, 2 Feb 2015 20:47:07 +0000 (15:47 -0500)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sat, 7 Feb 2015 10:44:55 +0000 (18:44 +0800)
commitc09babfab7ae8c7d79a5dce9d866fbb28b82dde4
treebe18492341b211fc4a1d64aaf8fb5add99e78426
parent692132b5b1c5ce97076915d4aed0c61513e18b03
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 <dick@softplc.com>
[pjh: rewrote commit log]
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/tty/serial/8250/8250_core.c