About Beaglebone Black device tree

[Christian Mauderer]

On 31/01/2020 17:43, Vijay Kumar Banerjee wrote:
> 
> 
> On Fri, Jan 31, 2020 at 9:59 PM Christian Mauderer <list at c-mauderer.de
> <mailto:list at c-mauderer.de>> wrote:
> 
>     On 31/01/2020 17:25, Christian Mauderer wrote:
>     > On 31/01/2020 16:04, Vijay Kumar Banerjee wrote:
>     >> Hi,
>     >>
>     >> While trying to run an rtems-littlevgl app on BBB, I found that
>     the device
>     >> tree generated from the freebsd source matching the freebsd-org
>     >> HEAD commit doesn't work with the app and framebuffer device fails
>     >> to open. This is most likely due to the changes in the freebsd dts
>     >> sources because of which the overlay isn't working as expected.
>     >
>     > If I remember correctly, SD card doesn't work either with a FDT
>     that is
>     > too new.
>     >
>     >>
>     >> I haven't had a detailed look at what's missing and the u-boot isn't
>     >> reporting any error in applying the overlay either. I checked
>     that the
>     >> device tree built from freebsd tree matching the following commit
>     >> works:
>     >> 19a6ceb89dbacf74697d493e48c388767126d418
>     >
>     > At the moment that's the right one. But that can change if someone
>     > updates libbsd again.
> 
>     And I have to correct myself: That is not the right one. The current
>     libbsd HEAD should work with 6b0307a0a5184339393f555d5d424190d8a8277a.
> 
> I meant to say that the framebuffer doesn't work with the current HEAD
> (6b0307).
> I checked with a previous commit, which is 19a6ce and found it working.
> I should have been clear in the problem statement, sorry about that. 

Thats not good. But the correct way would be to find out what's wrong
and fix it. Did they add a fix in a future FreeBSD version?

> 
>     >
>     >>
>     >> This brings up two questions:
>     >> 1. Should we add the commit hash in the user manual so that the
>     user can
>     >> build
>     >>     from source matching that commits instead of HEAD. This can be a
>     >> problem 
>     >>     as other codes ported from freebsd might break if the device tree
>     >> doesn't
>     >>     match the HEAD commit of freebsd-org
>     >
>     > Adding a fixed commit id isn't really a good idea either. It is nearly
>     > guaranteed that no one updates it if libbsd is updated. It would be
>     > better to add instructions how to find out which commit should be
>     used.
> 
>     The command would be:
> 
>         git ls-files -s freebsd-org
> 
>     It works regardless whether the sub-module is initialized or not.
> 
>     >
>     >>
>     >> 2. How do we manage the device tree overlays required by RTEMS or
>     libbsd?
>     >>     I guess only BBB uses an overlay currently. Can we add a BSD
>     license to
>     >>     the overlay and add it somewhere in rtems or rtems-libbsd
>     repository and
>     >>     maintain it?
>     >
>     > I think you wrote the overlay so you can add any license you want. But
>     > I'm really not sure where to put it. We currently don't have a
>     location
>     > for that. Do you have a good suggestion?
>     >
> 
> How about rtemsbsd/sys/dts/arm/overlays ?
> Following the freebsd tree freebsd/sys/dts/arm/overlays/ 

Following the FreeBSD tree is a good point. But would they be visible
there? Beneath that: We currently don't have support for building the
overlays. Do you have an idea how that could look like?

Best regards

Christian

> 
>     > Best regards
>     >
>     > Christian
>     >
>     >>
>     >> Best regards,
>     >> Vijay>
>     >> _______________________________________________
>     >> devel mailing list
>     >> devel at rtems.org <mailto:devel at rtems.org>
>     >> http://lists.rtems.org/mailman/listinfo/devel
>     >>
>