[U-Boot-Users] U-Boot and MPC857T?

[Gunnar Larisch <la@Softing.com>]

Hello!

On Wed, Jul 02, 2003 at 08:36:24AM +0200, Steven Scholz wrote:
> Wolfgang Denk wrote:
> >In message <3F014BE5.3080906@imc-berlin.de> you wrote:
> >
> >>has someone patched U-Boot to "support" the MPC857T?

Sorry, I am still using PPCBoot V1.6 and made a quick hack for some performance
tests.

> >>
> >>AFAIK it's basicly a MPC855T. So the only change would be to avoid a 
> >>boot message like:
> >>
> >>CPU:   unknown MPC855 (0x07000003) at 80 MHz: 4 kB I-Cache 4 kB 
> >>D-Cache FEC present
> >
> >
> >All  you  need  to  do  is  extend  the  list  of  types  defined  in
> >"cpu/mpc8xx/cpu.c" - a patch is welcome.
> 
> I'd love to present a patch.

Hope, this helps for a good patch.

> Could you please give me a pointer where to find information about the 
> values of
> 
> k = (immr << 16) | *((ushort *) & immap->im_cpm.cp_dparam[0xB0]);
> 
> ?
> I couldn't find some.

I couldn't neither. I patched the orginal check_CPU function for MPC855
and inserted a call like this:
+  case 0x07000003:
+       return (check_CPU_MPC857_HACK(clock, pvr, immr));
+       break;

so function check_CPU_MPC857_HACK is almost a copy of check_CPU.
the main differences in compare to check_CPU was this:
+  char  pre = 'X';
+  char *mid = "xx";
+  char *suf;
...
+  switch(k) {
+  case 0x07000003: mid = "T"; suf = "B"; m = 1; break;
+  default:                     suf = NULL;     break;
+  }
...
+  if (suf)
+       printf ("%cPC857%sZPnn%s", pre, mid, suf);
+  else
+       printf ("unknown MPC857 (0x%08x)", k);
+
+  printf(" at %s MHz:", strmhz(buf, clock));

> Is it possible to find out if it's a 855, 857 or 860 at runtime?

This would be really nice, that is the reason why I first tried the hack like
above, but we would have to modify some part of the macro concept.

> So that we don't have to rely on DEFINES?
> 
> FAIK MPC855T and MPC857T are basicly the same. So could put both on my 
> board without actually changing the firmware.
> Would be nice if u-boot could figure out which one is actually present.

I also thought to that, but it is not so easy, because of at least the
following Macros showed below.

We have our board with a MPC855T 50 MHz and two prototypes with a MPC857T 100
MHz. The CPU-Clock cannot be detected automatically. We need at
least the following differences:

#elif defined(CONFIG_100MHz)   /* for 100 MHz  = "50 MHz" |= SCCR_EBDF01 */
#define CFG_SCCR       (SCCR_TBS     | SCCR_EBDF01 | \
                        SCCR_COM00   | SCCR_DFSYNC00 | SCCR_DFBRG00  | \
                        SCCR_DFNL000 | SCCR_DFNH000  | SCCR_DFLCD000 | \
                        SCCR_RTSEL   | SCCR_DFALCD00)
#define CFG_PLPRCR ( (4-1)<<PLPRCR_MF_SHIFT | PLPRCR_TEXPS | PLPRCR_TMIST )
#define CONFIG_8xx_GCLK_FREQ    100000000
#else                  /* up to 50 MHz we use a 1:1 clock (CLKOUT=GCLK2) */
#define CFG_SCCR       (SCCR_TBS     | \
                        SCCR_COM00   | SCCR_DFSYNC00 | SCCR_DFBRG00  | \
                        SCCR_DFNL000 | SCCR_DFNH000  | SCCR_DFLCD000 | \
                        SCCR_RTSEL   | SCCR_DFALCD00)
#define CFG_PLPRCR ( (2-1)<<PLPRCR_MF_SHIFT | PLPRCR_TEXPS | PLPRCR_TMIST )
#define CONFIG_8xx_GCLK_FREQ     50000000
#endif /* CONFIG_...MHz */

also CFG_MAMR_PTA should be modified.

Best regards,

Gunnar Larisch
-- 
Gunnar Larisch
Dipl.-Ing.
Development
Softing AG
Richard-Reitzner-Allee 6
85540 Haar