[PATCH 2/2] serial: 8250_mtk: honor DT serial aliases

[Carlo Caione]

The Genio board DTs provide serial aliases for all enabled UARTs, but
the MTK 8250 driver still registered every port with the default line
number. If uart0 deferred and another UART probed first, the 8250 core
could still assign ttyS0 to the wrong port despite the DT aliases.

Read the serial alias during OF probe and seed uart.port.line before
registering the port so the 8250 core reserves the requested ttyS slot.

Signed-off-by: Carlo Caione <ccaione at baylibre.com>
---
 drivers/tty/serial/8250/8250_mtk.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
index e6a56cf54ae0..841d64f6a707 100644
--- a/drivers/tty/serial/8250/8250_mtk.c
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -8,6 +8,7 @@
 #include <linux/clk.h>
 #include <linux/io.h>
 #include <linux/module.h>
+#include <linux/of.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
 #include <linux/pinctrl/consumer.h>
@@ -521,7 +522,7 @@ static int mtk8250_probe(struct platform_device *pdev)
 	struct uart_8250_port uart = {};
 	struct mtk8250_data *data;
 	struct resource *regs;
-	int irq, err;
+	int irq, err, line;
 	struct fwnode_handle *fwnode = dev_fwnode(&pdev->dev);
 
 	irq = platform_get_irq(pdev, 0);
@@ -575,6 +576,10 @@ static int mtk8250_probe(struct platform_device *pdev)
 #endif
 
 	if (is_of_node(fwnode)) {
+		line = of_alias_get_id(pdev->dev.of_node, "serial");
+		if (line >= 0)
+			uart.port.line = line;
+
 		/* Disable Rate Fix function */
 		writel(0x0, uart.port.membase +
 			(MTK_UART_RATE_FIX << uart.port.regshift));

-- 
2.55.0