make PHYS_OFFSET determined at run time (unfinished)

[Ben Dooks]

On Wed, Jan 20, 2010 at 09:26:41AM +1300, Ryan Mallon wrote:
> Uwe Kleine-König wrote:
> > Hello,
> > 
> > I'm looking into making PHYS_OFFSET determined at run time.  I saw a
> > patch for it that already made it a few times on the list[1].
> > 
> > I'm not yet done, but first want to announce that I look into that to
> > prevent duplicate work---so if you intended to do the same let's look
> > together---and to post some clean up patches that are the result up to
> > now of my digging in the boot code.
> > 
> > I will send now three patches in reply to this mail, and later hopefully
> > more.
> > 
> > Best regards
> > Uwe
> > 
> > [1] e.g. http://thread.gmane.org/gmane.linux.ports.arm.kernel/53793/
> > 
> 
> One of the problems that got brought up previously was the 'make uImage'
> can end up generating unbootable images with runtime PHYS_OFFSET. The
> older format uImage's (pre 1.3.3) encode a load address (zrealaddr), so
> uImage's need to have a fixed load address encoded.
> 
> As I stated in the previous thread, this is _not_ a kernel issue,
> however it is no good having a kernel which contains support for two
> boards which boot from different address and then generating a uImage
> which can only boot on one of them without warning the user about this
> problem. Otherwise you are going to start getting "I did make uImage and
> my board won't boot" problems.
> 
> There are a few solutions to this problem:
> 1) Drop uImage make support and require users generate them manually.
> 2) Have a uImage offset config option to allow uImage users to specify
> what they want the load address to be. See:
> http://thread.gmane.org/gmane.linux.ports.arm.kernel/53151/focus=53230
> 3) Print an error if "make uImage" is run for a kernel which has more
> than one boot address (possible?)
> 4) Use FIT U-Boot images. This is supported from U-Boot 1.3.3 onwards,
> however a number of people are still using older U-Boots.

Or of course, boot zImages. I belive u-boot has support for zImage.
> 
> ~Ryan
> 
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> 
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-- 
-- 
Ben

Q:      What's a light-year?
A:      One-third less calories than a regular year.