[PATCH] serial: imx: Put DMA enabled UART in separate lock subclass

[Sascha Hauer]

The i.MX UART driver never uses DMA on UARTs providing the console.
Put the UART port lock in a separate subclass to avoid lockdep
complaining about possible deadlocks when the DMA driver issues
console messages under its own spinlock held.

Reported-by: Tim van der Staaij <Tim.vanderstaaij@xxxxxxxxxxxxx>
Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
---
 drivers/tty/serial/imx.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 7341d060f85cb..c30113cf5db85 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1458,8 +1458,10 @@ static int imx_uart_startup(struct uart_port *port)
 	imx_uart_writel(sport, ucr4 & ~UCR4_DREN, UCR4);
 
 	/* Can we enable the DMA support? */
-	if (!uart_console(port) && imx_uart_dma_init(sport) == 0)
+	if (!uart_console(port) && imx_uart_dma_init(sport) == 0) {
+		lockdep_set_subclass(&port->lock, 1);
 		dma_is_inited = 1;
+	}
 
 	spin_lock_irqsave(&sport->port.lock, flags);
 
-- 
2.39.2

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