[U-Boot] 4K padding of ARM DT blob

[Yehuda Yitschak]

Hey Simon 

Thanks for the clarification 

Just out of curiosity, how can the padding help modify the FDT in u-boot ?

Yehuda 

> -----Original Message-----
> From: sjg at google.com [mailto:sjg at google.com] On Behalf Of Simon Glass
> Sent: Wednesday, March 11, 2015 21:01
> To: Masahiro Yamada
> Cc: Tom Rini; Yehuda Yitschak; u-boot at lists.denx.de; Hanna Hawa
> Subject: Re: [U-Boot] 4K padding of ARM DT blob
> 
> Hi,
> 
> On 10 March 2015 at 23:48, Masahiro Yamada
> <yamada.masahiro at socionext.com> wrote:
> > Hi Yehuda, Tom, Simon,
> >
> >
> >
> > 2015-03-07 0:12 GMT+09:00 Tom Rini <trini at konsulko.com>:
> >> On Thu, Mar 05, 2015 at 06:20:35PM +0000, Yehuda Yitschak wrote:
> >>> Hey Tom
> >>>
> >>> In arch/arm/dts/Makfile: line 56
> >>> "DTC_FLAGS += -R 4 -p 0x1000"
> >>>
> >>> this tell the dtc tool to add a 4K padding to the device tree blob.
> >>>
> >>> i can't figure out why this is needed.
> >>> Its creating a 4KB penalty on the dtb file so i guess it has some
> justification.
> >>
> >> That's interesting and I don't see a corresponding thing in the kernel.
> >> Masahiro?  This dates back to the introduction of the Makefile and
> >> that's you in the git log, thanks!
> >
> > Not me!
> > I just converted the Makefile into Kbuild style.
> >
> >
> > The option "-R 4 -p 0x1000" was introduced by:
> >
> > commit bbb0b128c3956ac549471addc314702fbe0ace63
> > Author: Simon Glass <sjg at chromium.org>
> > Date:   Sat Oct 15 05:48:21 2011 +0000
> >
> >     fdt: Add support for embedded device tree (CONFIG_OF_EMBED)
> >
> >
> > Simon,
> > Looks like the 4K padding was introduced by you.
> > Can you explain why?
> 
> I think at the time perhaps we were thinking of modifying the FDT in early U-
> Boot init, but that did not happen. I think it can be dropped.
> Using my time machine I just sent a patch to do this a few weeks ago:
> 
> http://patchwork.ozlabs.org/patch/444847/
> 
> Regards,
> Simon