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Re: uboot for MIPS: need help to skip relocate uboot and start uboot fro

To: linux-mips@linux-mips.org
Subject: Re: uboot for MIPS: need help to skip relocate uboot and start uboot from RAM
From: Ray Dudu <raydudu@gmail.com>
Date: Thu, 03 Mar 2011 14:46:36 +0200
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Hi,
I'm not so familira with uboot, however, I done proprietary booter
implementation for my company. Similar functionality was required, for
different purposes actually, but it doesn't change the idea.

So in my booter code I done simple check of code location. In case when
the code detects that it is already in RAM, it skips memory/caches
initialization and self coping. Some useful pieces of code:
Supporting function.

------CUT-HERE--------
LEAF(set_ra)

        jr      ra
        nop

END(set_ra)
------CUT-HERE--------
Actually the check:
------CUT-HERE--------
        bal     set_ra      /* first get the current program counter */
        nop

        move    t0, ra

        li      t1, 0x10000000
        and     t1, t1, t0
        bne     zero, t1, 1f                /* code in ROM/flash */
        nop

        li      s3,0                    /* code in RAM */
        b       2f
        nop
1:
        /* jump to system initialization and code coping routine here */
2:
        /* continue normal boot */
------CUT-HERE--------

I suppose you can do similar in u-boot and it will be quite generic
solution. Such code can be executed from RAM and FLASH without need to
reconfigure and rebuild.


03.03.11 12:16, Pandurang Kale написав(ла):
> Hello Everyone,
> 
> We have MIPS based development board and I am trying to get the uboot up
> and running on it.
> We have a primary bootloader which check for the valid mod-image stored
> on the flash. This mod-image consist of header, uboot and linux kernel.
> Depending on the recent, active and stable imagethe primary bootloader
> first copies the uboot image. and later on we would copy the kernel
> image from uboot.
> 
> But when primary bootloader copies the uboot image to the RAM and passes
> the control to the uboot, uboot (MIPS version of start.S and
> arch/mips/lib/borad.c) tries to relocate the
> already copied image from RAM (the primary bootloader copied it to start
> of the RAM+1MB address) to top of the RAM (0x87fc0000) region thinking
> that the uboot image is stored in flash.
> 
> All I need to do is skip the uboot relocate code in MIPS version of
> uboot startup as the primary bootloader has already relocated the uboot
> from Flash to RAM and set up the stack pointer and other global data
> appropriately, which it does after relocation.
> I can see there is a switch for ARM processor,
> CONFIG_SKIP_RELOCATE_UBOOT, which skips the relocation of uboot code and
> tries to run the uboot from RAM. I
> cannot see a similar switch implemented for MIPS and didnt find any
> related thread anywhere in mailing list or on net.
> 
> Do we have similar ARM like switch to SKIP the RELOCATION? If not has
> anyone done this before?
> 
> I would really appreciate if you can guide me to overcome this issue to
> run the uboot cleanly skipping the relocation.
> 
> Thanks in advance,
> Pandu

-- 
Best regards,
RD18-UANIC


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