openwrt/target/linux/bcm27xx/patches-5.10/950-0031-amba_pl011-Don-t-use-DT-aliases-for-numbering.patch

From a79b4327445a827be28b9939592da8e812a19b29 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Tue, 23 Feb 2016 17:26:48 +0000
Subject: [PATCH] amba_pl011: Don't use DT aliases for numbering

The pl011 driver looks for DT aliases of the form "serial<n>",
and if found uses <n> as the device ID. This can cause
/dev/ttyAMA0 to become /dev/ttyAMA1, which is confusing if the
other serial port is provided by the 8250 driver which doesn't
use the same logic.
---
 drivers/tty/serial/amba-pl011.c | 5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -2599,7 +2599,12 @@ static int pl011_setup_port(struct devic
 	if (IS_ERR(base))
 		return PTR_ERR(base);
 
+	/* Don't use DT serial<n> aliases - it causes the device to
+	   be renumbered to ttyAMA1 if it is the second serial port in the
+	   system, even though the other one is ttyS0. The 8250 driver
+	   doesn't use this logic, so always remains ttyS0.
 	index = pl011_probe_dt_alias(index, dev);
+	*/
 
 	uap->old_cr = 0;
 	uap->port.dev = dev;