GSoC 2015: Raspberry Pi 2 Support

[Joel Sherrill]

On 5/5/2015 11:11 AM, Rohini Kulkarni wrote:
>
> Hi,
>
> I am working with the code for bsp hooks. I am referring to existing
> ARM multicore bsp codes, zync mainly. 
>
> 1. There are existing hooks for the raspberry pi. Where should the
> code for the  Pi2 hooks be added?
>
The Pi and Pi2 are remarkably similar so Pi2 should be placed inside the
Pi BSP directory.
There is already a Pi2 variant of that code built. But we know specific
places where there
are variances. Depending on the scope of what is different, it can be as
simple as
a cpp conditional in a .h to select a value or two implementations of a
single method
and the Makefile.am picking the right file to build based on the board
variant.

The big question to always ask is: Is this specific to the Pi2 and
incompatible with the Pi?

Since the Pi BSP is still missing capabilities, it is likely code common
to both will
be added this summer. For example, did the mailbox interface change? I
don't know
but would guess that it didn't.  Each new capability added needs that added.

And any differences need to be analyzed to pick the least intrusive way
to provide
alternate implementations. Or enable special code like the Pi2 SMP
support which
is dependent on --enable-smp and being a Pi2.
>
> 2. Am I right in understanding that I will have to implement A7
> specific functions as have been for A9? I am referring specifically to
> the arm-a9mpcore-start.h
>
Yes.

If the code is very similar between the a7 and a9, then a discussion
on devel@ should occur to decide the best way to minimize duplication.

If you end up with a7 specific code, you should follow the location and
naming patterns already established. That places it in
libbsp/arm/shared/...
so it can be used by any BSP with the right SMP core.


> I am referring to existing codes to locate and get hold of what needs
> to be done in the hooks. However, being new to such implementations, I
> am taking longer to understand the details. Any suggestions that might
> help here are welcome
>
The answer will depend on the factors listed above. When code can
be shared, we want to share it across as many BSPs as makes sense.
When it is unique to a specific BSP **variant** (e.g. Pi vs Pi2), then
you want to find the way to account for the variation in the least
intrusive code way possible.
>
> Thanks!
>
> On 1 May 2015 12:45, "Rohini Kulkarni" <krohini1593 at gmail.com
> <mailto:krohini1593 at gmail.com>> wrote:
>
>
>     Hi,
>
>     Excited to be a part of  this edition of GSoC! Thanks to everybody
>     for helping me get here and congratulations to all the
>     participating students!
>
>     So, now getting to work, firstly I wish to know, specifically from
>     my mentors, any changes that must be made to my proposed project
>     or schedule.
>
>     Secondly, are there any specifics for the development blog that we
>     need to create for the project? Over time what is the blog
>     expected to convey.
>
>     Also, I have to create a new wiki page for my project as none
>     exists. I want to know how to add one.
>
>     -- 
>     Rohini Kulkarni
>

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel.sherrill at OARcorp.com        On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
Support Available                (256) 722-9985

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