[PATCH v2 2/2] arm: mach-snapdrgon: misc: Simplify msm_generate_mac_addr()

[Stephan Gerhold]

The logic in msm_generate_mac_addr() was originally taken from the LK
bootloader where the serial number is a string and must be parsed first.
However, in U-Boot msm_board_serial() returns an u32 and
msm_generate_mac_addr() has quite complicated code that will first
print it as a hex string and then immediately parse it again.

What this function actually does at the end is to put the serial number
encoded as big endian (the order used for the hex string) into the u8 *mac.
Use put_unaligned_be32() to do that with bit shifts instead of going
through the string format.

This should be slightly more efficient and cleaner but does not result
in any functional difference.

Cc: Ramon Fried <rfried.dev at gmail.com>
Signed-off-by: Stephan Gerhold <stephan at gerhold.net>
---

Changes in v2:
  - Rebase on u-boot/master to fix conflict with recent changes
  - Add comment to clarify what put_unaligned_be32() does here

 arch/arm/mach-snapdragon/misc.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/arch/arm/mach-snapdragon/misc.c b/arch/arm/mach-snapdragon/misc.c
index fbd5f4d051..7d452f4529 100644
--- a/arch/arm/mach-snapdragon/misc.c
+++ b/arch/arm/mach-snapdragon/misc.c
@@ -9,6 +9,7 @@
 #include <common.h>
 #include <mmc.h>
 #include <asm/arch/misc.h>
+#include <asm/unaligned.h>
 
 /* UNSTUFF_BITS macro taken from Linux Kernel: drivers/mmc/core/sd.c */
 #define UNSTUFF_BITS(resp, start, size) \
@@ -41,16 +42,14 @@ u32 msm_board_serial(void)
 
 void msm_generate_mac_addr(u8 *mac)
 {
-	int i;
-	char sn[9];
-
-	snprintf(sn, 9, "%08x", msm_board_serial());
-
-	/* fill in the mac with serialno, use locally adminstrated pool */
+	/* use locally adminstrated pool */
 	mac[0] = 0x02;
-	mac[1] = 00;
-	for (i = 3; i >= 0; i--) {
-		mac[i + 2] = hextoul(&sn[2 * i], NULL);
-		sn[2 * i] = 0;
-	}
+	mac[1] = 0x00;
+
+	/*
+	 * Put the 32-bit serial number in the last 32-bit of the MAC address.
+	 * Use big endian order so it is consistent with the serial number
+	 * written as a hexadecimal string, e.g. 0x1234abcd -> 02:00:12:34:ab:cd
+	 */
+	put_unaligned_be32(msm_board_serial(), &mac[2]);
 }
-- 
2.32.0