mtd: bcm63xxpart: make sure CFE and NVRAM partitions are at least 64KiB

The CFE boot loader on BCM63XX platforms assumes itself and the NVRAM
partition to be 64 KiB (or erase block sized, if larger).
Ensure this assumption is also met when creating the partitions to
prevent accidential erasure of CFE or NVRAM.
Signed-off-by: NJonas Gorski <jonas.gorski@gmail.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/bcm63xxpart.c

@@ -36,6 +36,9 @@
 
 #define BCM63XX_EXTENDED_SIZE	0xBFC00000	/* Extended flash address */
 
+#define BCM63XX_MIN_CFE_SIZE	0x10000		/* always at least 64KiB */
+#define BCM63XX_MIN_NVRAM_SIZE	0x10000		/* always at least 64KiB */
+
 #define BCM63XX_CFE_MAGIC_OFFSET 0x4e0
 
 static int bcm63xx_detect_cfe(struct mtd_info *master)
@@ -74,6 +77,7 @@ static int bcm63xx_parse_cfe_partitions(struct mtd_info *master,
 	size_t retlen;
 	unsigned int rootfsaddr, kerneladdr, spareaddr;
 	unsigned int rootfslen, kernellen, sparelen, totallen;
+	unsigned int cfelen, nvramlen;
 	int namelen = 0;
 	int i;
 	char *boardid;
@@ -82,14 +86,18 @@ static int bcm63xx_parse_cfe_partitions(struct mtd_info *master,
 	if (bcm63xx_detect_cfe(master))
 		return -EINVAL;
 
+	cfelen = max_t(uint32_t, master->erasesize, BCM63XX_MIN_CFE_SIZE);
+	nvramlen = max_t(uint32_t, master->erasesize, BCM63XX_MIN_NVRAM_SIZE);
+
 	/* Allocate memory for buffer */
 	buf = vmalloc(sizeof(struct bcm_tag));
 	if (!buf)
 		return -ENOMEM;
 
 	/* Get the tag */
-	ret = master->read(master, master->erasesize, sizeof(struct bcm_tag),
-							&retlen, (void *)buf);
+	ret = master->read(master, cfelen, sizeof(struct bcm_tag), &retlen,
+			   (void *)buf);
+
 	if (retlen != sizeof(struct bcm_tag)) {
 		vfree(buf);
 		return -EIO;
@@ -106,8 +114,8 @@ static int bcm63xx_parse_cfe_partitions(struct mtd_info *master,
 
 	kerneladdr = kerneladdr - BCM63XX_EXTENDED_SIZE;
 	rootfsaddr = kerneladdr + kernellen;
-	spareaddr = roundup(totallen, master->erasesize) + master->erasesize;
-	sparelen = master->size - spareaddr - master->erasesize;
+	spareaddr = roundup(totallen, master->erasesize) + cfelen;
+	sparelen = master->size - spareaddr - nvramlen;
 	rootfslen = spareaddr - rootfsaddr;
 
 	/* Determine number of partitions */
@@ -131,7 +139,7 @@ static int bcm63xx_parse_cfe_partitions(struct mtd_info *master,
 	/* Start building partition list */
 	parts[curpart].name = "CFE";
 	parts[curpart].offset = 0;
-	parts[curpart].size = master->erasesize;
+	parts[curpart].size = cfelen;
 	curpart++;
 
 	if (kernellen > 0) {
@@ -151,8 +159,8 @@ static int bcm63xx_parse_cfe_partitions(struct mtd_info *master,
 	}
 
 	parts[curpart].name = "nvram";
-	parts[curpart].offset = master->size - master->erasesize;
-	parts[curpart].size = master->erasesize;
+	parts[curpart].offset = master->size - nvramlen;
+	parts[curpart].size = nvramlen;
 
 	/* Global partition "linux" to make easy firmware upgrade */
 	curpart++;