[U-Boot] [RFC PATCH] mpc85xx: move generic corenet to cpu/mpc85xxx

[Andy Fleming]

Valentin, sorry for the dup (forgot to copy the mailing list


On Fri, May 3, 2013 at 9:02 AM, Valentin Longchamp <
valentin.longchamp at keymile.com> wrote:

> This allows to use this code on non Freescale QorIQ boards. If I am
> right, there are currently only Freescale boards with a QorIQ Soc that
> is supported by u-boot, that's why this code was located there.
>
>
Well, the problem is that it is not necessarily the case that a
non-Freescale QorIQ board will want the same LAW, TLB, and pci setup as the
Freescale boards. This code is shared on our boards because our boards
share a common infrastructure. We use the same FPGA for board management
across these boards, and the SoC architectures are similar enough that this
code can be shared. It is unlikely that non-Freescale boards need:

#ifdef PIXIS_BASE
        SET_TLB_ENTRY(0, PIXIS_BASE, PIXIS_BASE_PHYS,
                      MAS3_SW|MAS3_SR, MAS2_I|MAS2_G,
                      0, 0, BOOKE_PAGESZ_4K, 0),
#endif

There are many decisions that need to be made when making a board port
regarding the allocation of LAWs and TLBs, and those decisions are highly
influenced by the design of the board. This is an odd case where, even if
your board is nearly identical to ours, it would be better to copy the
code. We may, at some point release another board which is close enough
that we can share the code, at which point we would (carefully) modify
these files to accommodate the new board. If there are unknown other boards
consuming these settings, it's far more complicated for both parties.

TLB and LAW settings are highly specific to the board. While some of the
information is similar across boards, most of the information in those
files is how to lay out a memory map for the devices on the chip and the
board. You don't want to blindly copy ours -- you want to tailor yours to
the board you have. This is an odd case where, even if you *did* want to
copy ours, you should actually make a separate copy. We made this a shared
file because the QorIQ boards share a similar architecture. If you look
through board/freescale/ for tlb.c, you'll see that every other board in
there has its own, despite the fact that many of the SoCs are quite similar.