[U-Boot] RFC: Aligning arch initialisation sequences

[Graeme Russ]

On 15/11/10 00:46, Reinhard Meyer wrote:
> Dear Wolfgang Denk,
> 
> To make it crystal clear now, and put the complete context:
> 
> That simple change would rid us of all alignment concerns:
> Setting stack to end of initial storage will certainly
> be aligned, and the auto_gd will be aligned as the
> toolchain deems necessary.
> 
> We would not need GENERATED_GBL_DATA_SIZE anymore.
> 
> The auto_gd space on stack will be valid even into the call
> to relocate_code.
> 
>> void board_init_f (ulong bootflag)
>> {
>> 	bd_t *bd;
>> 	init_fnc_t **init_fnc_ptr;
>> 	gd_t *id;
>> 	ulong addr, addr_sp;
>> +	gd_t auto_gd;
>>
>> 	/* Pointer is writable since we allocated a register for it */
>> -	gd = (gd_t *) (CONFIG_SYS_INIT_SP_ADDR);
>> +	gd =&auto_gd;
>> 	/* compiler optimization barrier needed for GCC>= 3.4 */
>> /* Q: why is that needed anyway ??? */
>> 	__asm__ __volatile__("": : :"memory");
>>
>> 	memset ((void*)gd, 0, sizeof (gd_t));
>> ....
>> 	debug ("relocation Offset is: %08lx\n", gd->reloc_off);
>> 	memcpy (id, (void *)gd, sizeof (gd_t));
>>
>> 	relocate_code (addr_sp, id, addr);
>>
>> 	/* NOTREACHED - relocate_code() does not return */
>> }
>>
>> This, and setting CONFIG_SYS_INIT_SP_ADDR to an aligned value in
>> initial storage (SRAM, pinned down Cache, or other) removes alot
>> of the headache about making stuff aligned.
>>
> 
> This three line change DOES NOT propose any different method
> of handling gd other then it is currently done.
> 
> It is ONLY a more elegant way to allocate the pre-relocation
> storage for gd.

On the proviso that gd is not needed _BEFORE_ board_init_f()

Regards,

Graeme