Beagle: FDT support in BSP as a GSoC project?

Chris Johns chrisj at
Sun Aug 11 22:50:05 UTC 2019

On 12/8/19 3:28 am, Joel Sherrill wrote:
> On Sun, Aug 11, 2019, 10:59 AM Christian Mauderer <list at
> <mailto:list at>> wrote:
>     Hello,
>     while mentoring Vijays GSoC project this year I noted that some drivers
>     in the Beagle BSPs have quite horrible hard coded values for things like
>     pinmux initialization. Maybe it would be a nice GSoC project for next
>     year to replace this stuff with a fdt based initialization. I would like
>     to ask for feedback before creating a ticket for it because it would
>     mean a quite big change for the BSP (maybe even the name - see below).
>     Basically such a project would include the following parts:
>     - Parse the pinmux settings from FDT and create a two part driver for a
>     'pinctrl-single' compatible FDT entry. One part generic, one device
>     specific (similar to FreeBSD or Linux).
>     - Remove pinmux initialization from all drivers.
>     - Initialize drivers based on the FDT (instead of functions like
>     bbb_register_i2c_1(...))
>     - Taking a more detailed look at the FDT what else could be initialized
>     from it (maybe clocks?)
>     It could be a quite nice project for a RTEMS beginner. Due to the
>     distributed initialization a lot of drivers have to be touched (at least
>     i2c, spi and pwm). So a potential student would get a nice overview over
>     the parts.
>     Note that this would be a big change for the BSP. Currently the BSP can
>     be used without an FDT (as far as I know). Only libbsd needs one. After
>     that a FDT would be mandatory. Despite that, I think that it would be an
>     improvement.
>     Maybe it would be possible to merge the four beagle* BSPs that we have
>     into only one "beagle" or "am33xx" BSP with that change. That would
>     allow to support new Beagle variants like the Pocket Beagle without much
>     effort (most likely only a change in the FDT).
>     What do you think? Should I create a ticket for it?

I love it. Yes please create a ticket.

> I think this is a good idea if we can still avoid bloating apps with all
> drivers. Make sure it has the right tags and shows up on the project page.

The beagle has a lot of RAM. Is this as important for this BSP?

> There must be a good diagnostic if the device tree doesn't meet minimum
> requirements. We don't want a failure to be hard to figure out. This is a
> general statement for all device tree bsps.



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