[U-Boot] QSPI XIP boot on am437x

[Albert ARIBAUD <albert.u.boot@aribaud.net>]

Hello Vignesh,

On Tue, 10 Nov 2015 14:29:54 +0530, Vignesh R <vigneshr@ti.com> wrote:
> Hi,
> 
> With commit 7ae8350f67eea("ti: armv7: Move SPL SDRAM init to the right
> place, drop unused CONFIG_SPL_STACK") QSPI XIP boot appears to be broken
> on AM437x SK EVM.
> 
> Following UART initialization code (as indicated by TODO) causes the XIP
> boot failure.
> 
> 
> In arch/arm/cpu/armv7/am33xx/board.c:
> @@ -275,9 +275,9 @@ void s_init(void)
>  #if defined(CONFIG_NOR_BOOT) || defined(CONFIG_QSPI_BOOT)
>         /* TODO: This does not work, gd is not available yet */
>        gd->baudrate = CONFIG_BAUDRATE;
>        serial_init();
>        gd->have_console = 1;
>  #endif
> 
> 
> I was able to boot successfully from QSPI by commenting out the above code.
> But, could you suggest me what needs to be done as part of TODO in order
> to get QSPI XIP boot working?

Can't answer specifically on am437x, but basically, the problem you
have here may be that the code is running in a C runtime environment in
which only the global data is writable. This global data is a struct
global_data (see include/asm-generic/global_data.h) which is supposed
to be pointed to by the variable GD.

Can you detail the failure you are encountering?

Typically, GD is set up from within function board_init_f_mem(), before
calling board_init_f(), or from arch/arm/lib/crt0.S.

So all depends on whether s_init() is executed before or after
board_init_f_mem().

If s_init() runs before board_init_f_mem(), then you must move it to
run after board_init_f_mem(). :)

If s_init() runs after board_init_f_mem() and you still have the issue,
then your problem would be that gd is badly initialized. Is your board
built for Thumb with a recent compiler, by any chance? I any case, can
you test the value of gd when reaching the gd->baudrate line above?

> Thanks!

NP.

> Regards
> Vignesh

Amicalement,
-- 
Albert.