Revert "serial: stm32: Merge hard IRQ and threaded IRQ handling into single IRQ handler"

This reverts commit f24771b as it is
reported to break the build.

Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/202301200130.ttBiTzfO-lkp@intel.com
Fixes: f24771b ("serial: stm32: Merge hard IRQ and threaded IRQ handling into single IRQ handler")
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Valentin Caron <valentin.caron@foss.st.com> # V3
Cc: Marek Vasut <marex@denx.de>
Cc: Johan Hovold <johan@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: gregkh

drivers/tty/serial/stm32-usart.c

@@ -797,9 +797,23 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr)
 		spin_unlock(&port->lock);
 	}
 
+	if (stm32_usart_rx_dma_enabled(port))
+		return IRQ_WAKE_THREAD;
+	else
+		return IRQ_HANDLED;
+}
+
+static irqreturn_t stm32_usart_threaded_interrupt(int irq, void *ptr)
+{
+	struct uart_port *port = ptr;
+	struct tty_port *tport = &port->state->port;
+	struct stm32_port *stm32_port = to_stm32_port(port);
+	unsigned int size;
+	unsigned long flags;
+
 	/* Receiver timeout irq for DMA RX */
-	if (stm32_usart_rx_dma_enabled(port) && !stm32_port->throttled) {
-		spin_lock(&port->lock);
+	if (!stm32_port->throttled) {
+		spin_lock_irqsave(&port->lock, flags);
 		size = stm32_usart_receive_chars(port, false);
 		uart_unlock_and_check_sysrq_irqrestore(port, flags);
 		if (size)
@@ -1001,8 +1015,10 @@ static int stm32_usart_startup(struct uart_port *port)
 	u32 val;
 	int ret;
 
-	ret = request_irq(port->irq, stm32_usart_interrupt,
-			  IRQF_NO_SUSPEND, name, port);
+	ret = request_threaded_irq(port->irq, stm32_usart_interrupt,
+				   stm32_usart_threaded_interrupt,
+				   IRQF_ONESHOT | IRQF_NO_SUSPEND,
+				   name, port);
 	if (ret)
 		return ret;
 
@@ -1585,6 +1601,13 @@ static int stm32_usart_of_dma_rx_probe(struct stm32_port *stm32port,
 	struct dma_slave_config config;
 	int ret;
 
+	/*
+	 * Using DMA and threaded handler for the console could lead to
+	 * deadlocks.
+	 */
+	if (uart_console(port))
+		return -ENODEV;
+
 	stm32port->rx_buf = dma_alloc_coherent(dev, RX_BUF_L,
 					       &stm32port->rx_dma_buf,
 					       GFP_KERNEL);