[U-Boot] FDT howto

[Jagan Teki]

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.

>
>>
>>>
>>>>
>>>>>
>>>>>>
>>>>>>    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..

Thanks,
Jagan.

> Regards,
> Simon
>
>>
>> Thanks,
>> Jagan.
>>
>>>
>>>>
>>>> Thanks,
>>>> Jagan.
>>>>
>>>>>
>>>>>>
>>>>>> I saw that all tegra boards config files are defining
>>>>>> CONFIG_DEFAULT_DEVICE_TREE if ie. the case dts is a compile time
>>>>>> option right.
>>>>>> am i correct?
>>>>>
>>>>> Yes - see above. This is convenient for testing and development.
>>>>>
>>>>>>
>>>>>> Please let me know your inputs.
>>>>>
>>>>> Regards,
>>>>> Simon
>>>>>
>>>>>>
>>>>>> --
>>>>>> Thanks,
>>>>>> Jagan.