From: Phil Elwell <phil@raspberrypi.org>
Date: Tue, 23 Feb 2016 17:26:48 +0000 (+0000)
Subject: amba_pl011: Don't use DT aliases for numbering
X-Git-Tag: archive/raspbian/4.9.82-1+deb9u3+rpi1_jessie~5^2~399
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=5121ebea3251799f923ab249e7016a027ab3b6c9;p=linux-4.9.git

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.
---

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index c00ab22afe9e..4d7a4ca2db3f 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -2496,7 +2496,12 @@ static int pl011_setup_port(struct device *dev, struct uart_amba_port *uap,
 	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;