serial: pl011: UPSTAT_AUTORTS requires .throttle/unthrottle

The driver must provide throttle and unthrottle in uart_ops when it
sets UPSTAT_AUTORTS. Add them using existing stop_rx &
enable_interrupts functions.

Fixes: 2a76fa2 (serial: pl011: Adopt generic flag to store auto RTS status)
Cc: stable <stable@kernel.org>
Cc: Lukas Wunner <lukas@wunner.de>
Reported-by: Nuno Gonçalves <nunojpg@gmail.com>
Tested-by: Nuno Gonçalves <nunojpg@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220614075637.8558-1-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: ij-intel

drivers/tty/serial/amba-pl011.c

@@ -1367,6 +1367,15 @@ static void pl011_stop_rx(struct uart_port *port)
 	pl011_dma_rx_stop(uap);
 }
 
+static void pl011_throttle_rx(struct uart_port *port)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+	pl011_stop_rx(port);
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
 static void pl011_enable_ms(struct uart_port *port)
 {
 	struct uart_amba_port *uap =
@@ -1788,9 +1797,10 @@ static int pl011_allocate_irq(struct uart_amba_port *uap)
  */
 static void pl011_enable_interrupts(struct uart_amba_port *uap)
 {
+	unsigned long flags;
 	unsigned int i;
 
-	spin_lock_irq(&uap->port.lock);
+	spin_lock_irqsave(&uap->port.lock, flags);
 
 	/* Clear out any spuriously appearing RX interrupts */
 	pl011_write(UART011_RTIS | UART011_RXIS, uap, REG_ICR);
@@ -1812,7 +1822,14 @@ static void pl011_enable_interrupts(struct uart_amba_port *uap)
 	if (!pl011_dma_rx_running(uap))
 		uap->im |= UART011_RXIM;
 	pl011_write(uap->im, uap, REG_IMSC);
-	spin_unlock_irq(&uap->port.lock);
+	spin_unlock_irqrestore(&uap->port.lock, flags);
+}
+
+static void pl011_unthrottle_rx(struct uart_port *port)
+{
+	struct uart_amba_port *uap = container_of(port, struct uart_amba_port, port);
+
+	pl011_enable_interrupts(uap);
 }
 
 static int pl011_startup(struct uart_port *port)
@@ -2225,6 +2242,8 @@ static const struct uart_ops amba_pl011_pops = {
 	.stop_tx	= pl011_stop_tx,
 	.start_tx	= pl011_start_tx,
 	.stop_rx	= pl011_stop_rx,
+	.throttle	= pl011_throttle_rx,
+	.unthrottle	= pl011_unthrottle_rx,
 	.enable_ms	= pl011_enable_ms,
 	.break_ctl	= pl011_break_ctl,
 	.startup	= pl011_startup,