debug("%s: erase addr=0x%x len 0x%x\n", dev->name, offset, len);
 
        div_u64_rem(len, spi_flash->page_size, &rem);
-       if (rem)
+       if (rem) {
+               printf("%s: len(0x%x) isn't the multiple of page size(0x%x)\n",
+                      dev->name, len, spi_flash->page_size);
                return -EINVAL;
+       }
        div_u64_rem(offset, spi_flash->page_size, &rem);
-       if (rem)
+       if (rem) {
+               printf("%s: offset(0x%x) isn't the multiple of page size(0x%x)\n",
+                      dev->name, offset, spi_flash->page_size);
                return -EINVAL;
+       }
 
        status = spi_claim_bus(spi);
        if (status) {