[OpenPower-Firmware] SBE questions

[Marty E. Plummer]

Hello.

So, I'm doing some preliminary work on the idea of a coreboot port for
p9 (specifically the talos ii based systems) and have a few questions I
can't seem to find a definitive answer for.

>From the bmc, I'm able to dump 8 eeprom images over i2c; it appears that
these are combined in some way to produce the 'real' image that executes,
but I'm unsure as to how this goes.

According to aspeed-bmc-opp-talos.dts there are two i2c busses hooked up
to the cpu-internal eeproms. i2c0 and i2c1 both have four i2c addresses
which hook up to a dumpable eeprom file in sysfs, addresses 0x54-0x57.
Each eeprom file dumped from sysfs is 32k in size, but what documentation
I have seen says that the seeprom is 64k in size, so I'm unsure what's
the correct combination (if any) of these files.

Further, using the p9_xip_tool report function against a dumped seeprom
image returns an error I'm not sure how to resolve:

```
p9_xip_tool 1-0054.eeprom -iv report                                                                                                  
Image section type : 0x00 "XIP image"
Magic number       : 0x584950205345504d "XIP SEPM"
Header version     : 0x3e
Link Address       : 0xffb0cc1a00000000
L1 Loader Address  : 0x00ff8002
L2 Loader Address  : 0x0000ffff
Kernel Address     : 0x000000ff
Image size         : 0x00000000 (0)
Normalized         : Yes
TOC Sorted         : Yes
Build Date         : 02/44/0000
Build Time         : 00:00
Build User         :
Build Host         : 1c2b4
Build Tag          : 

Section Table      :

    Name            Align   DD   Start        End          Size

   .header          0       0    0x00000000                0x00000000 (0)
   .fixed           0       0    0x0000015c   0xb301015b   0xb3010000 (-1291780096)
   .fixedtoc        0       0    0x00220000   0x016a07ff   0x01480800 (21497856)
   .toc             8       0    0x00000000                0x00000000 (0)
   .strings         0       4    0x00000000   0xf3ffffff   0xf4000000 (-201326592)
   .loader_text     0       0    0x000b0000                0x00000000 (0)
   .pibrepr_data    0       0    0x00000000   0x00020041   0x00020042 (131138)
   .text            0       0    0x04000000   0x33ffffff   0x30000000 (805306368)
   .data            5       72   0x00000800                0x00000000 (0)
   .base            0       0    0x01b1f004   0x01b1f0e5   0x000000e2 (226)
   .baseloader      0       0    0x00000000   0x0007ffff   0x00080000 (524288)
   .overrides       0       0    0x38730001   0x3f3e0400   0x06cb0400 (113968128)
   .rings           8       0    0x02be0800   0x02c11850   0x00031051 (200785)
   .overlays        0       8    0x00000000   0xf3ffffff   0xf4000000 (-201326592)
   .hbbl            45      68   0x004f0003   0x11670002   0x11180000 (286785536)

TOC Report

p9_xip_image.C:354 : Returning error code 1 : P9_XIP_IMAGE_ERROR
Header version mismatch; Expecting 9, found 62

ERROR: In command(): Command failed : P9_XIP_IMAGE_ERROR
```

As you can see, the 'Build Date' and 'Build Host' fields both appear to
be 'junk' data, and the header version also appears to be wrong somehow.
(this is executed against the eeprom on bus 0, address 0x54; the one on
bus 1 seems to be more or less the same). I realize the actual SBE image
written to the SEEPROMs is dynamically assembled at runtime, prior to the
write. Perhaps this impacts the header version above?

Overall the SBE code is a bit too verbose with too many layers of
indirection for me to easily make sense of by itself so I've been more
or less brought to instead doing RE work against the final binary, using
the source as a reference, so any help anyone could provide here would
be a great help.

Regards,
Marty