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

Michal Simek michal.simek at xilinx.com
Wed Mar 4 07:44:07 CET 2020

On 04. 03. 20 3:47, Simon Glass wrote:
> Hi Michal,
> On Mon, 2 Mar 2020 at 23:52, Michal Simek <michal.simek at 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 at 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 at 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 at 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?



More information about the U-Boot mailing list