change boot requirements [Was: make PHYS_OFFSET determined at run time (unfinished)]

[u.kleine-koenig@pengutronix.de (Uwe Kleine-König)]

Hello,

On Fri, Jan 22, 2010 at 12:58:31PM +0100, Uwe Kleine-K?nig wrote:
> just a short status report:  The code seems to work OK if PHYS_OFFSET is
> determined correctly.
> 
> The problem is when it does not.  Currently I place arch/arm/boot/Image
> at 0xa1008000[1] with PHYS_OFFSET being 0xa0000000.  Then
> arch/arm/boot/head.S guesses PHYS_OFFSET to be 0xa1000000 resulting
> __va(bank->start) of my only bank to be 0xbf000000.  And so this bank is
> discarded by sanity_check_meminfo as 0xbf000000 overlaps the vmalloc
> region.
> 
> So how to proceed?  These possiblities come to (my) mind:
> 
>  - parse the atag list to better guess phys_offset
>    (both zImage and Image would need to do that)
>  - require that zImage and Image are placed such that the guess is done
>    right (which is stupid for zImage as then the decompressor needs to
>    move the decompressed image)
>  - require the bootloader to pass phys_offset (r3?)
>  - make the ram mapping non-linear
>  - don't discard the whole bank, only the addresses overlaping the
>    vmalloc region
> 
> Anything else?  Preferences?  Thoughts?
I'd like to go forward here and if I don't hear anything here I'll start
requiring that the bootloader sets r3=PHYS_OFFSET as this seems the most
robust solution to me.

Best regards
Uwe

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Pengutronix e.K.                              | Uwe Kleine-K?nig            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |