Hi Albert,
Thanks for your response. Albert ARIBAUD wrote:
Hi Vamsi, Thanks for your response. Sorry for not mentioning the file name. its here uboot/arch/arm/cpu/arm920t/at91rm9200/lowlevel_init.S and also in uboot/board/samsung/smdk2410/lowlevel_init.S. My doubt is that as of now no relocation happened and the code is still being executed from flash rite, why would TEXT_BASE required in fetching the values from flash. This really confuses me.
Let me tell my understanding about. When the system starts u-boot.bin resides in the flash and starts executing start.S(by figuring out the entry point from u-boot.lds). And from u-boot.lds, the text section starts at 0x0000000 and other sections follow it. I really dont understand here the necessity of considering TEXT_BASE for writing SMRDATA values into registers as there is no RAM in the picture yet. This is the I would greatly appreciate a little detailed response.
Thanks very much.
Le 22/01/2011 05:18, krrish53 a écrit :
Hello everybody, I have a question pertaining to almost every lowlevel_init.S. The code goes like
/*make r0 relative the current location so that it*/ /*reads SMRDATA out of flash rather than memory*/ ldr r0,=SMRDATA ldr r1,_TEXT_BASE sub r10,r0,r1
I couldn't relate the code to comments made ahead of that(how does TEXT_BASE
- addrof(SMRDATA) yield the location of SMRDATA in flash. I totally dint
get it. Please enlighten me. I greatly appreciate any response.
It would be easier if you gave the precise source code origin, filename and location of the code you're mentioning. I took the u-boot-arm current master branch, and could not exactly find any occurrence of "sub r10, r0, r1" so I looked for an appraoching sequence, and found e.g. arch/arm/cpu/arm926ejs/at91/lowlevel_init.S, line 63. Is this what you meant?
/* memory control configuration */ /* this isn't very elegant, but what the heck */ ldr r0, =SMRDATA ldr r1, _MTEXT_BASE sub r0, r0, r1 add r2, r0, #80
If so, the code does not compute TEXT_BASE - SMRDATA, rather the reverse : SMRDATA - TEXT_BASE, .i.e. the relative address of SMRDATA with respect to the image start (depending on START_FROM_MEM, in Flash or physical RAM). I assume #80 is an absolute base address of the actual SMRDATA, but I'm no at91 specialist.
Thanks, Vamsi
Amicalement,
Albert. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot