[U-Boot] passing info from SPL to U-Boot

[Heiko Schocher]

Hello Simon, Tom,

I am just stumbeld on an am437x basd board over the problem to pass
the bootmode from SPL to U-Boot. On am437x the bootmode info get
overwritten from SPL stack, and I need this info in U-Boot.

Hack would be to move SPL stack to another address, but we loose
than 0xa000 size for stack ... I do not want to go this way..

I thought gd info is passed from SPL to U-Boot, but this is not the case!

Looking into

...
  75         bic     r0, r0, #7      /* 8-byte alignment for ABI compliance */
  76         mov     sp, r0
  77         bl      board_init_f_alloc_reserve
  78         mov     sp, r0
  79         /* set up gd here, outside any C code */
  80         mov     r9, r0
  81         bl      board_init_f_init_reserve

and common/init/board_init.c:

  99 void board_init_f_init_reserve(ulong base)
100 {
101         struct global_data *gd_ptr;
102
103         /*
104          * clear GD entirely and set it up.
105          * Use gd_ptr, as gd may not be properly set yet.
106          */
107
108         gd_ptr = (struct global_data *)base;
109         /* zero the area */
110         memset(gd_ptr, '\0', sizeof(*gd));
111         /* set GD unless architecture did it already */
112 #if !defined(CONFIG_ARM)
113         arch_setup_gd(gd_ptr);
114 #endif

gd is always initialized with zeros, no chance for passing infos from
SPL to U-Boot...

I really thought, that gd_t was intentionally designed for passing data
between different U-Boot states, but looking into gd_t definiton in
include/asm-generic/global_data.h it is a big ifdef mess and not useable
as an "API" between TPL/SPL and U-Boot ...

I thought also, that SPL detects for example ramsize and than passes
this info to U-Boot ...

But Ok, I found "common/init/handoff.c" which seems now the way to go, but:

./common/board_f.c

  281 static int setup_spl_handoff(void)
  282 {
  283 #if CONFIG_IS_ENABLED(HANDOFF)
  284         gd->spl_handoff = bloblist_find(BLOBLISTT_SPL_HANDOFF,
  285                                         sizeof(struct spl_handoff));
  286         debug("Found SPL hand-off info %p\n", gd->spl_handoff);
  287 #endif
  288
  289         return 0;
  290 }

There is gd->spl_handoff used ... how could this work at least on arm,
if gd is set to zeros on init ?

Do I miss something obvious?

bye,
Heiko
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