linux-kernel - [PATCH 4/4] MIPS: add bootargs-override property

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Date: Sun, 12 May 2024 15:25:11 +0200
From: Christian Marangi <ansuelsmth@...il.com>
To: Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
	Saravana Kannan <saravanak@...gle.com>,
	Arnd Bergmann <arnd@...db.de>,
	Helge Deller <deller@....de>,
	Javier Martinez Canillas <javierm@...hat.com>,
	Baoquan He <bhe@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jiaxun Yang <jiaxun.yang@...goat.com>,
	David Bauer <mail@...id-bauer.net>,
	Liviu Dudau <liviu@...au.co.uk>,
	Serge Semin <fancer.lancer@...il.com>,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-mips@...r.kernel.org
Cc: Christian Marangi <ansuelsmth@...il.com>
Subject: [PATCH 4/4] MIPS: add bootargs-override property

From: David Bauer <mail@...id-bauer.net>

Add support for the bootargs-override and bootargs-append property
to the chosen node similar to the one used on ipq806x or mpc85xx.

This is necessary, as the U-Boot used on some boards, notably the
Ubiquiti UniFi 6 Lite, overwrite the bootargs property of the chosen
node leading to a kernel panic on kernel loading (hardcoded root path or
other not compatible thing).

Signed-off-by: David Bauer <mail@...id-bauer.net>
[ rework and simplify implementation, add support for bootargs-append ]
Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
---
 arch/mips/kernel/setup.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 12a1a4ffb602..725e3f19f342 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -538,11 +538,23 @@ static int __init bootcmdline_scan_chosen(unsigned long node, const char *uname,
 	    (strcmp(uname, "chosen") != 0 && strcmp(uname, "chosen@0") != 0))
 		return 0;
 
-	p = of_get_flat_dt_prop(node, "bootargs", &l);
+	/*
+	 * Retrieve command line
+	 * bootargs might be hardcoded and overwrite by bootloader on
+	 * kernel load.
+	 * Check if alternative bootargs-override is present instead
+	 * first.
+	 */
+	p = of_get_flat_dt_prop(node, "bootargs-override", &l);
+	if (p == NULL || l == 0)
+		p = of_get_flat_dt_prop(node, "bootargs", &l);
 	if (p != NULL && l > 0) {
 		bootcmdline_append(p, min(l, COMMAND_LINE_SIZE));
 		*dt_bootargs = true;
 	}
+	p = of_get_flat_dt_prop(node, "bootargs-append", &l);
+	if (p != NULL && l > 0)
+		bootcmdline_append(p, min_t(int, strlen(boot_command_line) + l, COMMAND_LINE_SIZE));
 
 	return 1;
 }
-- 
2.43.0