[U-Boot] [PATCH v3] common/image.c: align usage of fdt_high with initrd_high

[Simon Glass]

Hi Shawn,

On Thu, Feb 9, 2012 at 10:51 AM, Shawn Guo <shawn.guo at linaro.org> wrote:
> Hi Simon,
>
> Thanks for looking at the patch.
>
> On 9 February 2012 09:37, Simon Glass <sjg at chromium.org> wrote:
> ...
>>>   fdt_high     - if set this restricts the maximum address that the
>>>                  flattened device tree will be copied into upon boot.
>>> +                 For example, if you have a system with 1 GB memory
>>> +                 at physical address 0x10000000, while Linux kernel
>>> +                 only recognizes the first 704 MB as low memory, you
>>> +                 may need to set fdt_high as 0x3C000000 to have the
>>> +                 device tree blob be copied to the maximum address
>>> +                 of the 704 MB low memory, so that Linux kernel can
>>> +                 access it during the boot procedure.
>>
>> I don't entirely understand that - 0x3c000000 is at a 768MB offset
>> into kernel space think - where does the 64MB difference come from?
>> Perhaps explain that a bit more.
>>
> All the numbers above come from the real case of Freescale i.MX6Q
> Sabrelite board:
>
> 0x2C000000 (704 MB) + 0x10000000 (physical base) = 0x3C000000

OK I see, thanks.

Regards,
Simon

>
> Regards,
> Shawn