[U-Boot] problem detecting CFI

[wpa at fastmail.fm]

I can fix this problem not but I really don't understand how the problem
happens in the first place. I found gp got changed in relocate_code in
file start.S. 

In relocate_code "function", the $gp is adjusted to point to the new
location, but somehow before program jumps to the relocated place, $gp
was changed. But I don't know where it is changed. So I used t8 register
to save the adjusted gp, and put it back before it jump to DRAM. But I
don't know why $gp was changed in the between. Can someone give me some
idea? I did not touch any thing else in this file.

        /*
         * Fix $gp:
         *
         * New $gp = (Old $gp - CONFIG_SYS_MONITOR_BASE) + Destination
         Address
         */
        move    t6, gp
        sub     gp, CONFIG_SYS_MONITOR_BASE
        add     gp, a2          /* gp now adjusted              */
        move    t8, gp          /*  add here <=== save gp               
        */

...

        /* Jump to where we've relocated ourselves.
         */
        move    gp, t8                        /* add here <=== copy gp
        back */
        addi    t0, s2, in_ram - _start
        jr      t0
        nop




On Thu, 01 Oct 2009 18:25 -0500, wpa at fastmail.fm wrote:
> I just found something interesting -
>
> In my previous email I thought the CFI detection was running from
> DRAM, but that assumption seems to be wrong. Previously I though it
> was running from DRAM because I traced the execution using BDI into
> mips/start">cpu/mips/start.S relocate_code, it runs to the place where
> it relocates itself. To be exact, here -
>
> addi t0, s2, in_ram - start jr t0 nop
>
> I checked and found the pc register changed to pointing to a SDRAM
> location, so relocation seems to be fine. I also load the symbol-file
> to the DRAM location at that point. But afterwards if I set breakpoint
> to board_init_r, the breakpoint is not triggered.
>
> Then I realized if I keep using the same symbol-file, the breakpoint
> at board_init_r can be triggered, and at that point, I can see the PC
> is still pointing to the flash.
>
> I don't understand how can the code, which has been relocated to SDRAM
> at one point, suddenly going back to run in the flash when it calls
> board_init_r. Can someone help me?
>
> Thanks.
>
>
> On Thu, 01 Oct 2009 16:47 -0500, wpa at fastmail.fm wrote:
> > I have a working u-boot 2008.10 on a mips 32 board and am trying to
> > port it over to u-boot 2009.06. So I used buildroot 2009.08 to build
> > the tool chain for my mips32 board as well as u-boot2009.06. I also
> > copied the previous u-boot initialization code to initialize timer,
> > serial port, ram and etc from u-boot 2008.10 to 2009.06.
> >
> > Right now the problem is the new u-boot 2009.06 does not detect cfi
> > of the flash. I am pretty sure u-boot is running from SDRAM when the
> > problem happens because the address is in the range of SDRAM. Please
> > let me know if you have any suggestion - I am running out of ideas.
> > I am attaching the printout from both the working u-boot 2008.10 and
> > u-boot 2009.06 below.
> >
> > Thanks a lot.
> >
> > U-Boot 2009.06 (Sep 30 2009 - 18:41:26)
> >
> > Reset Cause: Hardware Reset DRAM:  64 MB Top of RAM usable for U-
> > Boot at: 98000000 Reserving 139k for U-Boot at: 97fdc000 Reserving
> > 4352k for malloc() at: 97b9c000 Reserving 36 Bytes for Board Info
> > at: 97b9bfdc Reserving 36 Bytes for Global Data at: 97b9bfb8
> > Reserving 128k for boot params() at: 97b7bfb8 Stack Pointer at:
> > 97b7bf98 Now running in RAM - U-Boot at: 97fdc000 flash detect cfi
> > not found flash detect cfi not found
> >
> >
> > U-Boot 2008.10 (Sep 30 2009 - 11:37:03)
> >
> > Reset Cause: Hardware Reset DRAM:  64 MB Top of RAM usable for U-
> > Boot at: 98000000 Reserving 736k for U-Boot at: 97f44000 Reserving
> > 4352k for malloc() at: 97b04000 Reserving 44 Bytes for Board Info
> > at: 97b03fd4 Reserving 36 Bytes for Global Data at: 97b03fb0
> > Reserving 128k for boot params() at: 97ae3fb0 Stack Pointer at:
> > 97ae3f98 Now running in RAM - U-Boot at: 97f44000 flash detect cfi
> > fwc addr b0000000 cmd f0 f0 8bit x 8 bit fwc addr b0000000 cmd ff ff
> > 8bit x 8 bit fwc addr b0000055 cmd 98 98 8bit x 8 bit is= cmd 51(Q)
> > addr b0000010 is= 4f 51 fwc addr b0000555 cmd 98 98 8bit x 8 bit is=
> > cmd 51(Q) addr b0000010 is= 4f 51 fwc addr b0000000 cmd f0 f0f0
> > 16bit x 8 bit fwc addr b0000000 cmd ff ffff 16bit x 8 bit fwc addr
> > b00000aa cmd 98 9898 16bit x 8 bit is= cmd 51(Q) addr b0000020 is=
> > 5151 5151 is= cmd 52(R) addr b0000022 is= 5252 5252 is= cmd 59(Y)
> > addr b0000024 is= 5959 5959 device interface is 2 found port 2 chip
> > 1 port 16 bits chip 8 bits
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