Dear 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()
At least on ARM, board_init_f() is the first C function called after basic SoC initialisation in ASM.
And may patch does not move the point of availability of gd at all.
Best Regards, Reinhard