GSoC PRU device tree overlay

[Nils Hölscher]

Hi Vijay,

On Mon, 27 May 2019 at 12:15, Vijay Kumar Banerjee <vijaykumar9597 at gmail.com>
wrote:

>
>
>
> On Mon, May 27, 2019 at 1:24 PM Nils Hölscher <nilhoel1 at gmail.com> wrote:
>
>> Hi,
>>
>> I tried to rout the PRUs pins via device tree overlay this week.
>> Sadly I wasn't able to produce results on linux with this method.
>> Please check my blog post concerning this issue.
>>
>> https://nilshoel.home.blog/2019/05/27/setting-up-prus-pins-via-device-tree-files/
>>
>> It would be great if someone having experience with device tree overlay
>> could get me some feed back.
>> I will now move on to setting up RTEMS and porting the drivers.
>>
>> Hello Nils,
>
> I read your blog and had a look at the overlay. From first look at the
> overlay I noted that you're using `target-path`. I think target-path holds
> a path string like "/path" instead of a reference to your pruss. Maybe
> there should be a `target` field and you'll have to seth the target path
> manually or just remove it if you're not using it.
>
> A few pointers that helped me in general, to get an overlay working :
>  * always check for the -@ option while compiling with dtc
>
I am compiling on the bone with: dtc -O dtb -I dts -o
/lib/firmware/PRU-GPIO-EXAMPLE-00A0.dtbo -b 0 -@ PRU-GPIO-EXAMPLE-00A0.dts

>  * before applying using a bootscript in u-boot, it might be a good
>     idea to use the fdtoverlay tool ( in linux host) and apply it on your
>     host system.
>
 * If it applies well, then just decompile the dtb with the
>     dtc and have a look at the device you were targeting, if your changes
>     look nice and so far you didn't get any error during the building, open
>     u-boot and manually apply overlay using `fdt apply`.
>
> With a quick look these pointers might be helpful. I'm working on porting
> the i2c stack from FreeBSD to RTEMS and have used an overlay for the
> path and compatibility. Hope these pointers were of some help.
> I can explain any of the points above if they're not clear and you can post
> the error log here as well ( if you luckily get proper error messages  ;-)
> )
>
> Thank you for these helpful notes.
I will try them this week and report back.
It would be nice if you could tell me the command you use for decompiling
the files.

Best,
Nils

> Regards,
> Vijay
>
>> Best regards,
>> Nils Hölscher
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