[U-Boot] FDT howto

[Jagan Teki]

Hi Simon,

On Sun, Feb 24, 2013 at 11:50 PM, Simon Glass <sjg at chromium.org> wrote:
> Hi,
>
> On Sun, Feb 24, 2013 at 9:55 AM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>> Hi Simon,
>>
>> On Sun, Feb 24, 2013 at 11:18 PM, Simon Glass <sjg at chromium.org> wrote:
>>> Hi Jegan,
>>>
>>> On Sun, Feb 24, 2013 at 9:45 AM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>>>> Hi Simon,
>>>>
>>>> On Sun, Feb 24, 2013 at 11:08 PM, Simon Glass <sjg at chromium.org> wrote:
>>>>> Hi Jagan,
>>>>>
>>>>> On Sun, Feb 24, 2013 at 8:19 AM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>>>>>> Hi Simon,
>>>>>>
>>>>>> Thanks for your response, please find my below comments.
>>>>>>
>>>>>> On Sun, Feb 24, 2013 at 9:24 PM, Simon Glass <sjg at chromium.org> wrote:
>>>>>>> Hi Jagan,
>>>>>>>
>>>>>>> On Thu, Feb 21, 2013 at 9:03 AM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>>>>>>>> Hi All,
>>>>>>>>
>>>>>>>> I am planning to use devicetree on u-boot.
>>>>>>>> I have an experience to work with devicetree on Linux.
>>>>>>>>
>>>>>>>> For u-boot, I have read doc from doc/README.fdt-control.
>>>>>>>> I see some dts usages on tegra boards.
>>>>>>>>
>>>>>>>> I have lot of confusions with the concept itself.
>>>>>>>>
>>>>>>>> Is Linux and u-boot devicetree concept and build system are same?
>>>>>>>
>>>>>>> I don't really understand this question sorry. U-Boot and Linux use
>>>>>>> the device tree mainly for run-time configuration of drivers, so that
>>>>>>> the same driver code can operate on different boards.
>>>>>>
>>>>>> I am some how confusing the fdt usage in u-boot.
>>>>>> Because when compared to Linux, u-boot fdt setup mandatory to require
>>>>>> the CONFIG_DEFAULT_DEVICE_TREE
>>>>>> on the config file [from your previous comments].
>>>>>>
>>>>>> is this the only difference when compared to Linux i guess..is it?
>>>>>> Linux defconfig file does need to hot-code
>>>>>> the dts.
>>>>>
>>>>> Yes - that is a difference. Linux provides a way to build .dts files
>>>>> but it is not mandatory. At present it is mandatory with U-Boot, and
>>>>> only one file is built. It can easily be ignored though.
>>>>
>>>> Ok.
>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>> Suppose I have 4 boards J1, J2, J3 & J4 on my soc "emb".of vendor "vast"
>>>>>>>>    For this requirement I have
>>>>>>>>    board/vast/dts/J1.dts
>>>>>>>>    board/vast/dts/J2.dts
>>>>>>>>    board/vast/dts/J3.dts
>>>>>>>>    board/vast/dts/J4.dts
>>>>>>>>
>>>>>>>>    include/configs/emb_common.h ==> single configuration of all SOC
>>>>>>>> needed definitions
>>>>>>>>    like defconfig in Linux.
>>>>>>>>
>>>>>>>>    do I need any more files?
>>>>>>>
>>>>>>> That's enough for the basics I think.
>>>>>>
>>>>>> Is dtsi file require to add it on arch folder along with above.
>>>>>
>>>>> If your architecture is not one of those already supported (like arm
>>>>> tegra/exynos and x86) then yes you need to add this file in
>>>>> arch/<arch>/dts. What architecture are you using?
>>>>
>>>> My architecture is armv7, may be for me dtsi not required as arm is
>>>> existing architecture
>>>> to support fdt on u-boot.. is it?
>>>
>>> Which sub-arch? If it is tegra/exynos5250 then you might be OK. For
>>> something else, you should get the kernel's .dtsi file for that chip.
>>
>> I am having armv7, xilinx zynq soc..but i coun't get any .dtsi on kernel source.
>> may be I will create new one.
>
> OK, well if the kernel doesn't have FDT support yet then yes you will
> need to create a new one.
>
>>
>>>
>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>>    In emb_common.h i am defining
>>>>>>>>    CONFIG_OF_SEPARATE is it sufficient?
>>>>>>>
>>>>>>> And CONFIG_OF_CONTROL
>>>>>>>
>>>>>>>>
>>>>>>>>    My plan is to build u-boot and then build the dtb with specific
>>>>>>>> board and then combine.
>>>>>>>
>>>>>>> That's fine, and is how we do things on Chromium also. U-Boot tries to
>>>>>>> build an FDT even with CONFIG_OF_SEPARATE, so you need to put a
>>>>>>> default device tree file in your emb_common.h file that it can find.
>>>>>>> But you can ignore it, and for flashing your boards just use
>>>>>>> u-boot.bin plus whatever .dtb you want to select.
>>>>>>
>>>>>> So I will add the fdt support and then build the u-boot.
>>>>>> Is there any separate u-boot build command to build dts file.
>>>>>> My plan is to combine both u-boot and dtb.
>>>>>
>>>>> You can run dtc yourself if you like - see Makefile/dts for how it is
>>>>> done there. Once you have the .dtb binary, the easiest thing is to add
>>>>> it to the end of u-boot.bin, as described in README.fdt-control.
>>>>
>>>> Thanks, I tried with above setup for adding dts.
>>>> I have added simple dts file on my board.
>>>>
>>>> I got the below build error
>>>> /proj/mypc/u-boot/include/asm/gpio.h:1:27: fatal error:
>>>> asm/arch/gpio.h: No such file or directory
>>>> compilation terminated.
>>>> make[1]: *** No rule to make target `.depend.fdtdec', needed by
>>>> `.depend'.  Stop.
>>>>
>>>> is gpio.h is mandatory for fdt build?
>>>
>>> Yes because basic GPIO support is included. You can create one for
>>> your sub-arch and make it #include <asm-generic/gpio.h> as a starting
>>> point.
>>>
>>
>> Should I create an empty gpio.h file..it still asking some gpio
>> definitions right..
>
> It might be OK if you just have "#include <asm-generic/gpio.h>" in that file.

Thanks.

Finally I have created u-boot-dtb.bin.
for building dtb separately I have used
$ make DEVICE_TREE=zynq .. it creates a u-boot.dtb

is there any option for building separate name, for example I need to
create zynq.dtb

Thanks,
Jagan.