sunxi: On newer SoCs use words 1-3 instead of just word 3 from the SID

It seems that bytes 13-14 of the SID / bytes 1-2 from word 3 of the SID
are always 0 on H3 making it a poor candidate to use as source for the
serialnr / mac-address, and the other non constant words (1 and 2) also
have quite a few bits which are the same for some boards,

This commits switches to using the crc32 of words 1 - 3 to get a
more unique value for the mac-address / serialnr.

Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Corentin LABBE <clabbe.montjoie@gmail.com>
Cc: Amit Singh Tomar <amittomer25@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>

board/sunxi/board.c

@@ -27,6 +27,7 @@
 #endif
 #include <asm/gpio.h>
 #include <asm/io.h>
+#include <crc.h>
 #include <environment.h>
 #include <libfdt.h>
 #include <nand.h>
@@ -622,7 +623,24 @@ static void setup_environment(const void *fdt)
 	int i, ret;
 
 	ret = sunxi_get_sid(sid);
-	if (ret == 0 && sid[0] != 0 && sid[3] != 0) {
+	if (ret == 0 && sid[0] != 0) {
+		/*
+		 * The single words 1 - 3 of the SID have quite a few bits
+		 * which are the same on many models, so we take a crc32
+		 * of all 3 words, to get a more unique value.
+		 *
+		 * Note we only do this on newer SoCs as we cannot change
+		 * the algorithm on older SoCs since those have been using
+		 * fixed mac-addresses based on only using word 3 for a
+		 * long time and changing a fixed mac-address with an
+		 * u-boot update is not good.
+		 */
+#if !defined(CONFIG_MACH_SUN4I) && !defined(CONFIG_MACH_SUN5I) && \
+    !defined(CONFIG_MACH_SUN6I) && !defined(CONFIG_MACH_SUN7I) && \
+    !defined(CONFIG_MACH_SUN8I_A23) && !defined(CONFIG_MACH_SUN8I_A33)
+		sid[3] = crc32(0, (unsigned char *)&sid[1], 12);
+#endif
+
 		/* Ensure the NIC specific bytes of the mac are not all 0 */
 		if ((sid[3] & 0xffffff) == 0)
 			sid[3] |= 0x800000;