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

[Heiko Schocher]

Hello Simon, Tom,

Am 12.03.2019 um 09:21 schrieb 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?

Sorry for being so stupid, with:

common/board_f.c

  853 #ifdef CONFIG_BLOBLIST
  854         bloblist_init,
  855 #endif
  856         setup_spl_handoff,

and common/bloblist.c

216 int bloblist_init(void)
217 {
218         bool expected;
219         int ret = -ENOENT;
220
221         /**
222          * Wed expect to find an existing bloblist in the first phase of U-Boot
223          * that runs
224          */
225         expected = !u_boot_first_phase();
226         if (expected)
227                 ret = bloblist_check(CONFIG_BLOBLIST_ADDR,
228                                      CONFIG_BLOBLIST_SIZE);

gd->spl_handoff gets setup through bloblist_find() ...

But beside sandbox there is no current user currently, or?

$ grep -lr BLOBLIST_ADDR .
./test/bloblist.c
./include/bloblist.h
./common/bloblist.c
./common/Kconfig
./board/sandbox/README.sandbox
$

bye,
Heiko
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