env_nand.c: support falling back to redundant env when writing

Without this patch, when the currently chosen environment to be written
has bad blocks, saveenv fails completely. Instead, when there is
redundant environment fall back to the other copy. Environment reading
needs no adjustment, as the fallback logic for incomplete writes applies
to this case as well.

Signed-off-by: Phil Sutter <phil.sutter@viprinet.com>

common/env_nand.c

@@ -152,72 +152,57 @@ int writeenv(size_t offset, u_char *buf)
 	return 0;
 }
 
-#ifdef CONFIG_ENV_OFFSET_REDUND
-static unsigned char env_flags;
+struct env_location {
+	const char *name;
+	const nand_erase_options_t erase_opts;
+};
 
-int saveenv(void)
+static int erase_and_write_env(const struct env_location *location,
+		u_char *env_new)
 {
-	env_t	env_new;
-	ssize_t	len;
-	char	*res;
-	int	ret = 0;
-	nand_erase_options_t nand_erase_options;
+	int ret = 0;
 
-	memset(&nand_erase_options, 0, sizeof(nand_erase_options));
-	nand_erase_options.length = CONFIG_ENV_RANGE;
-
-	if (CONFIG_ENV_RANGE < CONFIG_ENV_SIZE)
-		return 1;
-
-	res = (char *)&env_new.data;
-	len = hexport_r(&env_htab, '\0', 0, &res, ENV_SIZE, 0, NULL);
-	if (len < 0) {
-		error("Cannot export environment: errno = %d\n", errno);
-		return 1;
-	}
-	env_new.crc	= crc32(0, env_new.data, ENV_SIZE);
-	env_new.flags	= ++env_flags; /* increase the serial */
-
-	if (gd->env_valid == 1) {
-		puts("Erasing redundant NAND...\n");
-		nand_erase_options.offset = CONFIG_ENV_OFFSET_REDUND;
-		if (nand_erase_opts(&nand_info[0], &nand_erase_options))
-			return 1;
-
-		puts("Writing to redundant NAND... ");
-		ret = writeenv(CONFIG_ENV_OFFSET_REDUND, (u_char *)&env_new);
-	} else {
-		puts("Erasing NAND...\n");
-		nand_erase_options.offset = CONFIG_ENV_OFFSET;
-		if (nand_erase_opts(&nand_info[0], &nand_erase_options))
-			return 1;
-
-		puts("Writing to NAND... ");
-		ret = writeenv(CONFIG_ENV_OFFSET, (u_char *)&env_new);
-	}
-	if (ret) {
-		puts("FAILED!\n");
+	printf("Erasing %s...\n", location->name);
+	if (nand_erase_opts(&nand_info[0], &location->erase_opts))
 		return 1;
-	}
-
-	puts("done\n");
 
-	gd->env_valid = gd->env_valid == 2 ? 1 : 2;
+	printf("Writing to %s... ", location->name);
+	ret = writeenv(location->erase_opts.offset, env_new);
+	puts(ret ? "FAILED!\n" : "OK\n");
 
 	return ret;
 }
-#else /* ! CONFIG_ENV_OFFSET_REDUND */
+
+#ifdef CONFIG_ENV_OFFSET_REDUND
+static unsigned char env_flags;
+#endif
+
 int saveenv(void)
 {
 	int	ret = 0;
 	ALLOC_CACHE_ALIGN_BUFFER(env_t, env_new, 1);
 	ssize_t	len;
 	char	*res;
-	nand_erase_options_t nand_erase_options;
+	int	env_idx = 0;
+	static const struct env_location location[] = {
+		{
+			.name = "NAND",
+			.erase_opts = {
+				.length = CONFIG_ENV_RANGE,
+				.offset = CONFIG_ENV_OFFSET,
+			},
+		},
+#ifdef CONFIG_ENV_OFFSET_REDUND
+		{
+			.name = "redundant NAND",
+			.erase_opts = {
+				.length = CONFIG_ENV_RANGE,
+				.offset = CONFIG_ENV_OFFSET_REDUND,
+			},
+		},
+#endif
+	};
 
-	memset(&nand_erase_options, 0, sizeof(nand_erase_options));
-	nand_erase_options.length = CONFIG_ENV_RANGE;
-	nand_erase_options.offset = CONFIG_ENV_OFFSET;
 
 	if (CONFIG_ENV_RANGE < CONFIG_ENV_SIZE)
 		return 1;
@@ -228,22 +213,29 @@ int saveenv(void)
 		error("Cannot export environment: errno = %d\n", errno);
 		return 1;
 	}
-	env_new->crc = crc32(0, env_new->data, ENV_SIZE);
-
-	puts("Erasing Nand...\n");
-	if (nand_erase_opts(&nand_info[0], &nand_erase_options))
-		return 1;
+	env_new->crc   = crc32(0, env_new->data, ENV_SIZE);
+#ifdef CONFIG_ENV_OFFSET_REDUND
+	env_new->flags = ++env_flags; /* increase the serial */
+	env_idx = (gd->env_valid == 1);
+#endif
 
-	puts("Writing to Nand... ");
-	if (writeenv(CONFIG_ENV_OFFSET, (u_char *)env_new)) {
-		puts("FAILED!\n");
-		return 1;
+	ret = erase_and_write_env(&location[env_idx], (u_char *)env_new);
+#ifdef CONFIG_ENV_OFFSET_REDUND
+	if (!ret) {
+		/* preset other copy for next write */
+		gd->env_valid = gd->env_valid == 2 ? 1 : 2;
+		return ret;
 	}
 
-	puts("done\n");
+	env_idx = (env_idx + 1) & 1;
+	ret = erase_and_write_env(&location[env_idx], (u_char *)env_new);
+	if (!ret)
+		printf("Warning: primary env write failed,"
+				" redundancy is lost!\n");
+#endif
+
 	return ret;
 }
-#endif /* CONFIG_ENV_OFFSET_REDUND */
 #endif /* CMD_SAVEENV */
 
 int readenv(size_t offset, u_char *buf)