[U-Boot] [PATCH] image: Don't relocate ramdisk to highmem

[Wolfgang Denk]

Dear Thierry Reding,

In message <20130711190849.GA17212 at dhcp-172-17-186-34.nvidia.com> you wrote:
> 
> > This depends a lot on a number of things.  For example, you should be
> > able to use a ramdisk in NOR flash directly, i. e. without loading it
> > to RAM first - especially if it;s a comprtessed ramdis image, and the
> > Kernel will copy/uncompress it anyway.  Depending on your memory map
> > the address range of the NOR flash may be way outside (and above) that
> > of the system RAM.  Are you sure your changes will not break any such
> > usage?
> 
> As far as I can tell, the only place where initrd_high is used is to
> allocate an area from RAM that's used to relocate the ramdisk to. In
> case where the ramdisk is directly in NOR and isn't supposed to be
> copied anyway, this code should never be run.

Agreed.  I'm not sure this is what's happening currently, though.

> So maybe one other alternative would be to check whether the current
> location of the ramdisk is within the low memory area and only relocate
> otherwise. Does that match your expectation?

Appears to make sense, indeed.  But I have to admit that I'm not deep
enough into the details of this code at the moment to make a qualified
statement.

> > ...because default behaviour was do do nothing. Now you do something,
> > so this should be documented.
>
> The default behaviour was to not restrict loading to high memory at all,
> which is what the comment said:
>
> 	/* not set, no restrictions to load high */
> 	initrd_high = ~0;
>
> The patch that I posted changes the above to this:
>
> 	/* make sure to put ramdisk in low memory */
> 	initrd_high = getenv_bootm_low() + getenv_bootm_mapsize();
>
> Doesn't that accurately describe the change?

I think this shouldbe added to the function header (too).

Best regards,

Wolfgang Denk

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