[U-Boot-Users] current simple 8260 platform as start...

[Yuli Barcohen]

>>>>> Wolfgang Denk writes:

    Wolfgang> Actually this is bad advice.  The *ADS boards have some
    Wolfgang> special features which you will not find on any other
    Wolfgang> board. Also, the implementation of the MPC8260ADS has some
    Wolfgang> serious problems which have not been fixed for ages
    Wolfgang> because the board is one of the many orphaned (i. e. not
    Wolfgang> maintained) boards.

    Rune> Like what? I'm interested because I've used the 8266ADS board
    Rune> as basis for our custom board. (Omitting some stuff like their
    Rune> PLA based boot config)

    Wolfgang> Like the fact that CFG_DEFAULT_IMMR definition in
    Wolfgang> MPC8260ADS.h will bring you nasty kernel crashes the first
    Wolfgang> time you want to boot your Linux kernel.

CFG_DEFAULT_IMMR can't cause any crash. It only tells to U-Boot
initialisation code where to find IMMR to change it to
CFG_IMMR. CFG_IMMR was unusable, it's right (its value was copied from
the board's manual just like the entire memory map), but it was fixed
long time ago by my patches.

    Wolfgang> Like the fact that there is seems to be need for a
    Wolfgang> proprietary version of jffs2_part_info() (because of a
    Wolfgang> broken flash layout?)

No, no, the flash is OK. At least, I think it's OK. I introduced JFFS2
support so I have to explain. The board provides two sources of HRCW:
the FPGA (BCSR) and the flash. Many boards have got two flashes: small
one for boot and large one for filesystem, etc. MPC826xADS/PQ2FADS has
only one, and it's flash SIMM, so 8MB, 16MB, and 32MB flash can be
supported by simple replacement of the SIMM. HRCW occupies only first
bytes of the SIMM but since flash is erased by blocks, entire block (on
4x8bit SIMM it's 256KB) wasted. I prefer to use BCSR-supplied HRCW but
didn't want to touch Motorola-provided value in the flash either. So I
burn the U-Boot at 0xFFF00000 (8MB SIMM starts at 0xFF800000). In such a
configuration, I have the range 0xFF840000-0xFFEFFFFF available for
JFFS2. Standard jffs2_part_info() allows to specify first filesystem
sector but not last. It "thinks" that the filesystem spans to the flash
end. This is the reason why proprietary version of jffs2_part_info()
appeared. Of course, different flash layout can be chosen.

    Wolfgang> Etc.

    Wolfgang> The fact alone that the board is listed under "orphaned"
    Wolfgang> should make you think.

-- 
========================================================================
 Yuli Barcohen       | Phone +972-9-765-1788 |  Software Project Leader
 yuli at arabellasw.com | Fax   +972-9-765-7494 | Arabella Software, Israel
========================================================================