[PATCH 2/2] ARM: bcm2835: Detect system revision

[Jonathan Neuschäfer]

The Raspberry Pi bootloader provides a revision code[0] in the
devicetree, at /system/linux,revision. The downstream kernel then uses
this DT property to fill the system_rev variable, which is exposed to
userspace via the "Revision" field in /proc/cpuinfo. Some software[1]
relies on this in order to determine the Raspberry Pi model.

This patch ports the revision detection from the downstream Raspberry Pi
kernel.

[0]: https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#new-style-revision-codes
[1]: https://github.com/hzeller/rpi-rgb-led-matrix/blob/a3eea997a9254b83ab2de97ae80d83588f696387/lib/gpio.cc#L247
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@xxxxxxx>
---
 arch/arm/mach-bcm/board_bcm2835.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/arm/mach-bcm/board_bcm2835.c b/arch/arm/mach-bcm/board_bcm2835.c
index bfc556f7672039..2a7b7ba3cd6c73 100644
--- a/arch/arm/mach-bcm/board_bcm2835.c
+++ b/arch/arm/mach-bcm/board_bcm2835.c
@@ -9,6 +9,7 @@

 #include <asm/mach/arch.h>
 #include <asm/mach/map.h>
+#include <asm/system_info.h>

 #include "platsmp.h"

@@ -23,7 +24,17 @@ static const char * const bcm2835_compat[] = {
 	NULL
 };

+static void __init bcm2835_init(void)
+{
+	struct device_node *np = of_find_node_by_path("/system");
+	u32 val;
+
+	if (!of_property_read_u32(np, "linux,revision", &val))
+		system_rev = val;
+}
+
 DT_MACHINE_START(BCM2835, "BCM2835")
 	.dt_compat = bcm2835_compat,
 	.smp = smp_ops(bcm2836_smp_ops),
+	.init_machine = bcm2835_init,
 MACHINE_END

--
2.43.0