Chapter 50. Using Yaffs with RedBoot

It is possible to link Yaffs into RedBoot and use it to boot an executable image stored on a NAND array.

This is done by configuring and building RedBoot largely in the normal way. You will need to add CYGPKG_FS_YAFFS and CYGPKG_IO_FILEIO to your configuration, plus their attendant dependencies.

The presence of CYGPKG_IO_FILEIO activates the fs series of RedBoot commands. The following (edited) transcript illustrates how they might be used in concert with other RedBoot commands to store an ELF image on a NAND partition, load it back and execute:

RedBoot> fs mount -d onboard/0 -t yaffs /nand
yaffs: restored from checkpoint
RedBoot> load -r -h my.tftp.ip.address -b %{freememlo} my.image
Using default protocol (TFTP)
Raw file loaded 0xa013f000-0xa01554b3, assumed entry at 0xa013f000
RedBoot> fs write /nand/myimg.elf
RedBoot> fs list /nand                                                          
   1 drwxr-xr-x  0 size      0 .
   1 drwxr-xr-x  0 size      0 ..
 262 -rw-r--r--  0 size  91316 myimg.elf
   2 drwxr-xr-x  0 size      0 lost+found
RedBoot> load -m file /nand/myimg.elf
RedBoot> go
Hello, NAND world!

Note: When you command RedBoot to execute an image, it first synchronises all mounted filesystems. Therefore, provided these filesystems support the synchronisation operation (which Yaffs does), it is not always necessary to unmount them before invoking an image.

Memory considerations under RedBoot

RedBoot traditionally has very limited requirements for memory management; the main need is for there to be free space in RAM at the correct (physical) address to load an image before jumping to it.

Introducing Yaffs brings with it not just the need to have dynamically allocatable RAM (CYGPKG_MEMALLOC), but enough to replay the filesystem journal. This must be balanced against the need for RAM to load images into.

When the CYGPKG_MEMALLOC package is present in RedBoot, by default a small (64k) heap is set up so that the maximum RAM possible is available for loading images. This is not enough to support Yaffs in any circumstances, so the following definition has been included in the yaffs.cdl file:

requires        { CYGPKG_REDBOOT implies (CYGMEM_REDBOOT_WORKSPACE_HEAP_SIZE >= 0x00014000) }

Caution

This declaration only provideds the bare minimum heap required to mount a trivial Yaffs filesystem. More will be required for all but the simplest of cases and it is recommended that you test for typical use in your environment. Refer also to the Section called Memory requirements in Chapter 49.

It is recommended that, should you wish to make a filesystem usable by RedBoot, your platform HAL should make a similar declaration in its CDL to establish an appropriate heap size. For example, the platform HAL for the EA LPC2468 OEM board - which has a 128MB NAND chip on-board - contains the following declaration:

requires        { (CYGPKG_REDBOOT && CYGPKG_FS_YAFFS) implies (CYGMEM_REDBOOT_WORKSPACE_HEAP_SIZE >= 0x20000) }

Tip: If you wish to experiment with restricted heaps to determine much memory your application actually uses under Yaffs, you may find the option CYGSEM_MEMALLOC_INVOKE_OUT_OF_MEMORY of use.

2017-02-09
Documentation license for this page: eCosPro License