[U-Boot] [PATCH] POST: Added ECC memory test for mpc83xx.

[Kim Phillips]

On Thu, 8 Apr 2010 09:49:08 +0300
Michael Zaidman <michael.zaidman at gmail.com> wrote:

> On Wed, Apr 7, 2010 at 7:01 PM, Joakim Tjernlund
> <joakim.tjernlund at transmode.se> wrote:
> >>
> >> On Wed, Apr 7, 2010 at 6:10 PM, Timur Tabi <timur.tabi at gmail.com> wrote:
> >> > On Wed, Apr 7, 2010 at 9:47 AM, Michael Zaidman
> >> > <michael.zaidman at gmail.com> wrote:
> >> >
> >> >> The version #2 of the patch is located here
> >> >> http://lists.denx.de/pipermail/u-boot/2010-April/069579.html
> >> >
> >> > What is ppcDWstore(), and why do you use it sometimes instead of
> >> > __raw_writel()?  I see the code for ppcDWstore:
> >> >
> >> >        .globl  ppcDWstore
> >> > ppcDWstore:
> >> >        lfd     1, 0(r4)
> >> >        stfd    1, 0(r3)
> >> >        blr
> >> >
> >> > I just don't understand why it exists.
> >> >
> >>
> >> This is the fastest way to copy 64 bit words.
> >
> > hmm, not all boards have a FPU(8xx and 832x). How are lfd and stfd handled
> > there?
> >
> >  Jocke
> >
> The ppcDWstore/ ppcDWload code is mpc83xx specific, so the mpc8xx is
> not relevant here. The e300c1 and e300c3 have FPU while e300c2 has

right (which also suggests it's badly named (at least since the advent
of the e300c2)).

> not. The lfd/stfd instructions load/store data from/to memory to/from
> FPRs. It looks like these instructions are performed by Load/Store
> Unit and rather require FPRs presence than FPU.  The block diagram of
> the e300c2 core in the e300coreRM (Rev3, 12/2006) specifies FPR File
> and its connection to the Load/Store Unit. On other hand the
> "1.3.1.1.2 Floating-Point Registers (FPRs)" chapter says that FPRs are
> not included in the e300c2 core. Can someone clarify this?

The documentation is confusing: the e300c2 has its FPU chopped off -
the FP registers are simply not there.

this is a good catch by Jocke - it would be best if generic 83xx code
didn't depend on the ppcDW* accessors.

Kim