[U-Boot] FDT howto
Jagan Teki
jagannadh.teki at gmail.com
Fri Mar 1 22:21:35 CET 2013
Hi Simon,
On Sat, Mar 2, 2013 at 1:54 AM, Simon Glass <sjg at chromium.org> wrote:
> Hi Jagan,
>
> On Fri, Mar 1, 2013 at 11:14 AM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>> Hi Simon,
>>
>> On Fri, Mar 1, 2013 at 10:07 AM, Simon Glass <sjg at chromium.org> wrote:
>>> Hi Jagan,
>>>
>>> On Thu, Feb 28, 2013 at 12:29 PM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>>>> Hi Simon,
>>>>
>>>> On Thu, Feb 28, 2013 at 7:22 PM, Simon Glass <sjg at chromium.org> wrote:
>>>>> Hi Jagan,
>>>>>
>>>>> On Thu, Feb 28, 2013 at 3:14 AM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>>>>>> Hi Simon,
>>>>>>
>>>>>> On Mon, Feb 25, 2013 at 4:40 AM, Simon Glass <sjg at chromium.org> wrote:
>>>>>>> Hi Jagan,
>>>>>>>
>>>>>>> On Sun, Feb 24, 2013 at 10:58 AM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>>>>>>>> Hi Simon,
>>>>>>>>
>>>>>>>> On Sun, Feb 24, 2013 at 11:55 PM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>>>>>>>>> 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
>>>>>>>
>>>>>>> No - but you can just use 'mv' in a script external to the U-Boot build system.
>>>>>>>
>>>>>>>>
>>>>>>>> Some how I am able to create a fdt build on my target.
>>>>>>>> But what is this gpio mandatory, because currently my target currently
>>>>>>>> need a GPIO setup.
>>>>>>>> Add ing gpio.h/ with equivalent definitions is an extra overhead is
>>>>>>>> it? please explain.
>>>>>>>
>>>>>>> It is just a header file - unless you actually use the GPIO functions,
>>>>>>> you can compile with -ffunction-sections and you won't get the GPIO
>>>>>>> code included. Anyway, the overhead is small, if any.
>>>>>>
>>>>>> OK, Thanks for your information.
>>>>>>
>>>>>> I have few quires regarding getting details from devicetree nodes.
>>>>>> 1) In case of drivers, I think we need add the MACROS on
>>>>>> // lib/fdtdec.c
>>>>>> static const char * const compat_names[COMPAT_COUNT] = {
>>>>>> is it?
>>>>>
>>>>> Yes that's what is normally done. At present it mostly just provides a
>>>>> way to register existing FDT use in U-Boot.
>>>>
>>>> OK.
>>>>
>>>>>
>>>>>> 2) What is the procedure for DDR base and size information getting
>>>>>> memory {
>>>>>> reg = <0x00000000 0x40000000>;
>>>>>> };
>>>>>> I need to get the above details from memory node of dts and
>>>>>> updated while doing
>>>>>> dram_init()
>>>>>> is it possible in u-boot right now?
>>>>>
>>>>> There is no particular support for dram_init(). You could call
>>>>> fdtdec_decode_region() to get the information.
>>>>
>>>> Actually we may get the info through memory node using
>>>> fdtdec_decode_region() for
>>>> dram_init(), but the problem seems like other than this the SDRAM base
>>>> and SDSIZE are using in
>>>> CONFIG_SYS_MEMTEST_START and CONFIG_SYS_MEMTEST_END.
>>>>
>>>> As these are part of configuration macros, I don't clear how we can
>>>> get the base,sizes from dts and assign these
>>>> areas..any suggestions..?
>>>
>>> Well this is because configuration has traditionally been done with
>>> CONFIG defines instead of device tree. CONFIG_OF_CONTROL is a
>>> relatively new feature in U-Boot.
>>>
>>> If you are wanting to control the memtest area from device tree, you
>>> might consider adding something to the '/config' node, since this is
>>> where we tend to put general configuration. You probably can't test
>>> all of memory, so you need to select the region.
>>
>> Thanks for your information.
>>
>> I am able to get the memory information using fdtdec_decode_region().
>>
>> So my CONFIG_SYS_SDRAM_BASE and CONFIG_SYS_SDRAM_SIZE dependencies
>> on board file got resolved. but there is a dependency for
>> CONFIG_SYS_SDRAM_BASE on
>> arch/arm/lib/board.c.
>>
>> I have some thinking about this dependency to remove can we declare
>> ram_base like ram_size
>> so-that in ddr_init we can assign this value.. is my thinking valid..???'
>
> Yes that sounds reasonable. For that you could perhaps use the memory
> {} node, like:
>
> memory {
> reg = <0x40000000 0x80000000>;
> };
I will confirm my logic here for better clarification.
typedef struct global_data {
phys_size_t ram_size; /* RAM size */
+ phys_size_t ram_base; /* RAM base */
} gd_t;
in boards files:
---
int ddr_init() {
//
get the memory info from dts store it on start and size
//
gd->ram_start = start;
gd->ram_size = size;
gd->bd->bi_dram[0].start = start;
gd->bd->bi_dram[0].size = size;
}
Please comment.
Thanks,
Jagan.
>
> Regards,
> Simon
>
>>
>> Any suggestions..
>>
>> Thanks,
>> Jagan.
>>
>>>
>>>>
>>>>>
>>>>>> 3) and same case for chosen also..are these implemented currently.
>>>>>
>>>>> The bootargs environment variable is placed in the kernel FDT when
>>>>> booting the kernel. But 'chosen' is not used in the U-Boot FDT. This
>>>>> is support instead for a '/config' node - see e.g.
>>>>> fdtdec_get_config_int().
>>>>
>>>> OK, thank you.
>>>>
>>>> Thanks,
>>>> Jagan.
>>>
>>> Regards,
>>> Simon
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