tty: serial: qcom_geni_serial: Fix UART hang

If a serial console write occured while a UART transmit command was
waiting for a done signal then no further data would be sent until
something new kicked the system into gear. If there is already data
waiting in the circular buffer we must re-enable the tx watermark so we
receive the expected interrupts.
Signed-off-by: Ryan Case <ryandcase@chromium.org>
Reviewed-by: Evan Green <evgreen@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/qcom_geni_serial.c

@@ -440,6 +440,7 @@ static void qcom_geni_serial_console_write(struct console *co, const char *s,
 	bool locked = true;
 	unsigned long flags;
 	u32 geni_status;
+	u32 irq_en;
 
 	WARN_ON(co->index < 0 || co->index >= GENI_UART_CONS_PORTS);
 
@@ -474,6 +475,13 @@ static void qcom_geni_serial_console_write(struct console *co, const char *s,
 		 * has been sent, in which case we need to look for done first.
 		 */
 		qcom_geni_serial_poll_tx_done(uport);
+
+		if (uart_circ_chars_pending(&uport->state->xmit)) {
+			irq_en = readl_relaxed(uport->membase +
+					SE_GENI_M_IRQ_EN);
+			writel_relaxed(irq_en | M_TX_FIFO_WATERMARK_EN,
+					uport->membase + SE_GENI_M_IRQ_EN);
+		}
 	}
 
 	__qcom_geni_serial_console_write(uport, s, count);