u-boot nand flash boot debug on t2080

[sophie_yang_a]

Hi Experts:

Here is uboot booting related issue want to check with you.

Thanks a lot for your time!!

Background:

After DDR can be init successfully in init script(we use on-chip mem not DIMM, we add some GPIO operation before/after enbale DDR) , we go ahead to burn u-boot into Nand Flash and try to boot/debug u-boot from Nand Flash.

Question Description:
Under the description of T2080 datasheet and uboot source codes, after power-on reset, the processor starts at 0xfffffffc and the code is first executed in the last 4K page(0xfffff000-0xffffffff) in flash, but when we do some test, we found the real process looks like:
1) after power-on, looks the first 8K data will be copied to SRAM(IFC) by PBL, and then setting PLL etc. parameter based on RCW.
2) because we need to boot from NAND, so PBI will also be needed, PBL will run the PBI instruction to copy codes from SRAM(IFC) to SRAM(CPC)
3) for temporarily inited TLB only can access 4k bytes mem, so the codes will do some more init on LAW and TLB to get ability to access the rest of the memory space, the switch to ram to run the rest uboot codes

And under the guide of AN4876, we try to debug u-boot with the following steps:
1, burn u-boot-with-spl-pbl.bin(QorIQ-SDK-V2.0-20160527-yocto/build_t2080rdb-64b/tmp/work/t2080rdb_64b-fsl-linux/u-boot-qoriq/2016.01+fslgit-r0/git/T2080RDB_NAND_config) into flash

2, run u-boot.elf image after connect to target via USB TAP,  do reset let it go into resetvec, then do single step let it run into start.S one by one.

But on my side, after reset operation, it will stop at 0xfffffffc, if go forward(step out), it will hang in 0x700, can not go further any more.

It means there is no correct instruction in 0xfffffffc, checked in u-boot's link script(arch/powerpc/cpu/mpc85xx/u-boot-nand_spl.lds), I found:
/*******************************************************/
SECTIONS
{
        . = 0xfff00000;
        .text : {
                *(.text*)
        }

.......
        .resetvec ADDR(.text) + RESET_VECTOR_OFFSET : {
                KEEP(*(.resetvec))
        } = 0xffff
.......
#define RESET_VECTOR_OFFSET 0x1ffc /* IFC has 8K sram */
#elif defined(CONFIG_FSL_ELBC)
#define RESET_VECTOR_OFFSET 0xffc /* LBC has 4k sram */
/*******************************************************/
There is no setting in 0xfffffffc.

And checked via readelf tool, I found the .text was put into 0x201000:
/**********************************************/
Section Headers:
  [Nr] Name
       Type            Addr     Off    Size   ES   Lk Inf Al
       Flags
  [ 0]
       NULL            00000000 000000 000000 00   0   0  0
       [00000000]:
  [ 1] .text
       PROGBITS        00201000 011000 067f1c 00   0   0 4096
       [00000006]: ALLOC, EXEC
/**********************************************/

So, currently, looks our u-boot still not get into start.S(arch/powerpc/cpu/mpc85xx/start.S), befor start.S, the running env should be setup by hardware setting(PBL,RCW), to boot from NAND, if we miss some important operation?

And do you have some comments about our understanding on the nand flash booting sequnce of t2080?

BTW, if DDR was inited in hardware init script(which was done by codewarrior), disable DDR init in u-boot will be okay when debugging?

[addiyi]

You could try to debug uboot for entry point using this https://community.nxp.com/docs/DOC-100403 

Adrian

[liujianbo]

Hi  Adrian:

Thanks for your suggestion!

When I try to debug u-boot under the guide of this doc, looks it did not run into the codes of start.S in u-boot, it stop at 0x700, it should jump to here for it did not fetch valid instruction in 0xffff_fffc.

So I doubt: I use the wrong uboot image(it include rcw, pbl, uboot) for nand flash boot, there(0xffff_fffc) should be a jump instruction, but from the uboot image, the jump instruction(4bff f004) is not located in this address, do I need some further config before build a nand flash boot image from sdk 2.0?

/************************************************************/

002a8f0: 0000 0000 4bff f004 0913 8000 0000 0000  ....K...........
002a900: 0913 80c0 0000 0000 0813 8040 6e1d 37a4  ...........@n.7.

/************************************************************/

[addiyi]

In CodeWarrior try to import and use uboot spl image.

[liujianbo]

Hi Stoica:

Thanks for your suggestion, after burn u-boot-with-spl-pbl.bin into nand flash,  and debug it with u-boot-spl elf file, it worked! It can debug start.S codes.

But u-boot-spl is only a lite version, if I want to debug into a completely u-boot, which elf image should I use?

Thanks a lot for your time!!

[addiyi]

Uboot spl image is used for first stage to initialize the hardware. You can use this image to debug the uboot code before relocation. After that, you should use the Uboot image, set a hardware breakpoint to a simbol after relocation and continue debugging.