On 03/02/11 18:01, Aneesh V wrote: > Hello Graeme, > > On Thursday 03 February 2011 02:31 AM, Graeme Russ wrote: > [snip ..] >>> Yes. These are variables that otherwise would go to BSS. I do this >>> because I need them before SDRAM initialization. One of this is the gd >>> structure. I allocate gd structure in .data that is in IRAM. >>> Why I need gd before SDRAM? Because I try to initialize serial console >>> as early as possible and this code has some reference to gd. >>> >> >> Which is a perfectly normal scenario and the way things have always been. >> There should have been no need to shuffle gd around because of console >> initialisation. >> >> And as I understand it, gd itself does not get statically 'allocated' in >> the u-boot image per-se (i.e. not in .data and not in .bss) - Only the >> pointer to it is allocated. In most arches, this pointer is itself not >> in .data or .bss but rather in a fixed reserved register. In the new x86 >> (final patches coming soon), the pointer is allocated in .data with a >> preset initialised value pointing into Cache-As-RAM (i.e. IRAM). Prior to >> relocation, the gd pointer variable points to somewhere in IRAM / CAR and >> after relocation, gd gets copied into the heap and the gd pointer adjusted >> to point to the new permanent copy. > > Please note that SPL starts executing from IRAM and not > FLASH (copied there by ROM code). So we have .data available > immediately. Actually we do not need gd except to reuse some code from > u-boot that uses it. Declaring gd as a static variable was just a > convenience decision.
Ah, silly me - I missed the fact this was SPL. Makes more sense now :) > > If I were to allocate it separately I would have to allocate it in the > same IRAM and I may end up reserving more space than needed to allow > for future expansion. IRAM space is at a premium. So, declaring it as a > static variable helps in allocating only as much space as is needed. > Makes sense Regards, Graeme _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
