[U-Boot] RFC: Aligning arch initialisation sequences

[Wolfgang Denk]

Dear Albert ARIBAUD,

In message <4CE0221A.7030502 at free.fr> you wrote:
> 
> Alright, then I think we should document how we comply, or do not
> comply, with GNU EABI / AAPCS (maybe a README.arm that people could read
> up) -- and I think if there is a way to access GD both before and after
> relocation without making a register unavailable to the whole u-boot
> code, then we should use it.

By the way - it should be not difficult to use a normal extern pointer
to reference the global data; see
"arch/powerpc/include/asm/global_data.h":

194 #if 1
195 #define DECLARE_GLOBAL_DATA_PTR     register volatile gd_t *gd asm ("r2")
196 #else /* We could use plain global data, but the resulting code is bigger */
197 #define XTRN_DECLARE_GLOBAL_DATA_PTR    extern
198 #define DECLARE_GLOBAL_DATA_PTR     XTRN_DECLARE_GLOBAL_DATA_PTR \
199                                     gd_t *gd
200 #endif

When I implemented this code I tested both versions. There is not
much of a difference, except that the register based version results
in smaller code.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
You are an excellent tactician, Captain. You let your second in  com-
mand attack while you sit and watch for weakness.
	-- Khan Noonian Singh, "Space Seed", stardate 3141.9