[PATCH v4 2/2] arch: arm: Show the serial number from devicetree in cpuinfo

[contact@paulk.fr (Paul Kocialkowski)]

This grabs the serial number shown in cpuinfo from the serial-number devicetree
property in priority. When booting with ATAGs (and without device-tree), the
provided number is still shown instead.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
---
 arch/arm/include/asm/system_info.h |  1 +
 arch/arm/kernel/setup.c            | 23 +++++++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/system_info.h b/arch/arm/include/asm/system_info.h
index 720ea03..3860cbd40 100644
--- a/arch/arm/include/asm/system_info.h
+++ b/arch/arm/include/asm/system_info.h
@@ -17,6 +17,7 @@
 
 /* information about the system we're running on */
 extern unsigned int system_rev;
+extern const char *system_serial;
 extern unsigned int system_serial_low;
 extern unsigned int system_serial_high;
 extern unsigned int mem_fclk_21285;
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 1d60beb..b501754 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -93,6 +93,9 @@ unsigned int __atags_pointer __initdata;
 unsigned int system_rev;
 EXPORT_SYMBOL(system_rev);
 
+const char *system_serial;
+EXPORT_SYMBOL(system_serial);
+
 unsigned int system_serial_low;
 EXPORT_SYMBOL(system_serial_low);
 
@@ -821,8 +824,25 @@ arch_initcall(customize_machine);
 
 static int __init init_machine_late(void)
 {
+	struct device_node *root;
+	int ret;
+
 	if (machine_desc->init_late)
 		machine_desc->init_late();
+
+	root = of_find_node_by_path("/");
+	if (root) {
+		ret = of_property_read_string(root, "serial-number",
+					      &system_serial);
+		if (ret)
+			system_serial = NULL;
+	}
+
+	if (!system_serial)
+		system_serial = kasprintf(GFP_KERNEL, "%08x%08x",
+					  system_serial_high,
+					  system_serial_low);
+
 	return 0;
 }
 late_initcall(init_machine_late);
@@ -1091,8 +1111,7 @@ static int c_show(struct seq_file *m, void *v)
 
 	seq_printf(m, "Hardware\t: %s\n", machine_name);
 	seq_printf(m, "Revision\t: %04x\n", system_rev);
-	seq_printf(m, "Serial\t\t: %08x%08x\n",
-		   system_serial_high, system_serial_low);
+	seq_printf(m, "Serial\t\t: %s\n", system_serial);
 
 	return 0;
 }
-- 
1.9.1