[PATCH 1/2] Makefile: Add environment variable DEVICE_TREE to header

From: Simon Glass <sjg@chromium.org>
To: u-boot@lists.denx.de
Subject: [PATCH 1/2] Makefile: Add environment variable DEVICE_TREE to header
Date: Wed, 4 Mar 2020 10:51:27 -0700	[thread overview]
Message-ID: <CAPnjgZ2ye-V02tx0C6Sc5=gPXb3fd105V1HVAAXrVuRVOnxAhA@mail.gmail.com> (raw)
In-Reply-To: <f9599076-dfa0-8cd5-53f7-d6fa11c099cb@xilinx.com>

Hi Michal,

On Tue, 3 Mar 2020 at 23:44, Michal Simek <michal.simek@xilinx.com> wrote:
>
> On 04. 03. 20 3:47, Simon Glass wrote:
> > Hi Michal,
> >
> > On Mon, 2 Mar 2020 at 23:52, Michal Simek <michal.simek@xilinx.com> wrote:
> >>
> >> On 02. 03. 20 20:47, Simon Glass wrote:
> >>> Hi Michal,
> >>>
> >>> On Fri, 28 Feb 2020 at 04:03, Michal Simek <michal.simek@xilinx.com> wrote:
> >>>>
> >>>> On 26. 02. 20 16:33, Simon Glass wrote:
> >>>>> Hi Michal,
> >>>>>
> >>>>> On Tue, 18 Feb 2020 at 09:02, Michal Simek <michal.simek@xilinx.com> wrote:
> >>>>>>
> >>>>>> Users have option to overwrite default device tree
> >>>>>> (CONFIG_DEFAULT_DEVICE_TREE) via environment variable DEVICE_TREE.
> >>>>>>
> >>>>>> Feature has been added long time ago by commit 74de8c9a1672
> >>>>>> ("dts/Makefile: Build the user specified dts") for a little bit different
> >>>>>> reason.
> >>>>>>
> >>>>>> But this variable can be also used for different purpose like choosing
> >>>>>> proper configuration from FIT image in SPL.
> >>>>>> And this is the functionality I would like to use on Xilinx Zynq devices
> >>>>>> that current u-boot.img can be composed in the same way based on OF_LIST
> >>>>>> and different configuration is taken based on platform specific SPL.
> >>>>>> SPL requires low level ps7_init_gpl configuration that's why different
> >>>>>> boards require different SPL with fixed board_fit_config_name_match().
> >>>>>>
> >>>>>> Signed-off-by: Michal Simek <michal.simek@xilinx.com>
> >>>>>> ---
> >>>>>>
> >>>>>> I have done it in this way but maybe there is any smarter way how this can
> >>>>>> be done. Also macro name can change if you want.
> >>>>>
> >>>>> Can you please add a bit of documentation to doc/README.fdt-control ?
> >>>>
> >>>> This feature is cover by documentation in this file already. What
> >>>> exactly do you think that should be added?
> >>>>
> >>>
> >>> Then I suppose I am confused as to what this patch does. I thought it
> >>> was allowing U-Boot to pass the DT to Linux, which wasn't previously
> >>> supported?
> >>
> >> Just a note this is also not supported and would be good to have support
> >> for it.
> >>
> >> The patch is putting device tree name as macro to header and I am using
> >> this value just in zynq SPL to choose proper dtb file from u-boot.img.
> >>
> >> On ZynqMP generic platform I am using mkimage_fit_atf.sh script to
> >> automatically fill default configuration.
> >> https://gitlab.denx.de/u-boot/u-boot/blob/master/arch/arm/mach-zynqmp/mkimage_fit_atf.sh#L94
> >> And I didn't want to create different u-boot.img/itb for Zynq that's why
> >> SPL has device tree built it directly in SPL.
> >>
> >> As I said maybe there is smarter way how to do it but this was the one I
> >> used.
> >> In our case SPL another way could be to put filename from ps7_init_*
> >> files and save it as variable and use it.
> >
> > OK I see. So are you using OF_CONTROL for SPL?
>
> Yes.

OK ta.

Reviewed-by: Simon Glass <sjg@chromium.org>

Regards,
Simon