--- zzzz-none-000/linux-3.10.107/drivers/mtd/chips/map_rom.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/drivers/mtd/chips/map_rom.c	2021-02-04 17:41:59.000000000 +0000
@@ -11,6 +11,7 @@
 #include <linux/errno.h>
 #include <linux/slab.h>
 #include <linux/init.h>
+#include <linux/of.h>
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/map.h>
 
@@ -28,6 +29,15 @@
 	.module	= THIS_MODULE
 };
 
+static unsigned int default_erasesize(struct map_info *map)
+{
+	const __be32 *erase_size = NULL;
+
+	erase_size = of_get_property(map->device_node, "erase-size", NULL);
+
+	return !erase_size ? map->size : be32_to_cpu(*erase_size);
+}
+
 static struct mtd_info *map_rom_probe(struct map_info *map)
 {
 	struct mtd_info *mtd;
@@ -47,8 +57,9 @@
 	mtd->_sync = maprom_nop;
 	mtd->_erase = maprom_erase;
 	mtd->flags = MTD_CAP_ROM;
-	mtd->erasesize = map->size;
+	mtd->erasesize = default_erasesize(map);
 	mtd->writesize = 1;
+	mtd->writebufsize = 1;
 
 	__module_get(THIS_MODULE);
 	return mtd;