Interested in BSP's (No idea where to start?)

[Joel Sherrill]

On Tue, Nov 26, 2019 at 2:06 PM Niteesh <gsnb.gn at gmail.com> wrote:

> Do both raspberry pi and raspberrypi2 use the same BSP? If not how to
> build for raspberry pi 2
>

Yes both use the same BSP family with some configuration settings based on
the BSP name/variant. See the configure.ac

--target=arm-rtems5 --enable-rtemsbsp=raspberrypi2


> I couldn't find any datasheet's for BCM2711(raspberrypi4), could only find
> for BCM2835 (raspberrypi1):
> https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
>

I found this page which links to a preliminary data sheet for the BCM2711
plus
the data sheets for the SoCs the other Pis use.


> but I think we can maybe use the Linux device tree for raspberry pi as a
> reference,
>
> https://github.com/raspberrypi/linux/blob/rpi-4.19.y/arch/arm/boot/dts/bcm2838.dtsi
>
> https://github.com/raspberrypi/linux/blob/rpi-4.19.y/arch/arm/boot/dts/bcm2838-rpi-4-b.dts
>

There are BSPs which use device trees now but if the difference is just
some a few base address and
maybe clock settings, I personally wouldn't add device tree support to the
BSP at this point.


>
>
> These are some changes that I found out through google:
> 1) Peripheral base address is now moved to 0x7E000000
> 2) There's a mention of ARM's GIC400 @ 0x40041000 but probably is only the
> distributor since the old CPU interface is still there @ 0x40000000
>

These are the type of things you are looking for. What's different.

It is possible some of the peripherals changed also but maybe not any
impacting being
able to run a basic RTEMS application (console and clock).

I highly recommend following up in a new thread with a better subject so
people will
recognize it and help.

Good luck

--joel


>
> On Tue, Nov 26, 2019 at 7:19 PM Joel Sherrill <joel at rtems.org> wrote:
>
>>
>>
>> On Tue, Nov 26, 2019 at 5:42 AM Niteesh <gsnb.gn at gmail.com> wrote:
>>
>>> Hii, everyone
>>> I am interested in contributing to RTEMS, specifically to the arm based
>>> BSP's. I am a sophomore in electronics and communication engineering
>>> interested in operating systems, and systems programming. I have written
>>> small drivers and libraries for Arduino, bare metal avr chips to interface
>>> with sensors. I would like to take it a bit further by learning about
>>> ARM-based devices.
>>>
>>> I have completed the hello world task for GSOC. As I said early I am
>>> interested in contributing to the drivers and BSP section for most likely
>>> raspberry pi and beaglebone. But I have no idea how to proceed further, any
>>> suggestions on where to start and is it okay to ask tons of questions?
>>> because I had a look at the previous year's project ideas and very little
>>> made sense to me. I am ready to put in my best effort just need some
>>> guidance from your side.
>>>
>>
>> This is a hard question to answer. There is a balance of something
>> interesting to do with not sending you on a quest. One extreme would be a
>> full BSP from scratch for some expensive hardware that you don't have and
>> shouldn't even try to afford. The other extreme is something so simple that
>> it isn't interesting. At the same time, it should be useful to the
>> community.
>>
>> I thought a little while about this and think updating the raspberrypi
>> BSP to support the pi3/pi4 should be a useful and tractable BSP issue to
>> address. It is also useful to the community.
>>
>> Discussions when this was brought up before indicate that the precise
>> System on Chip model changed from the 2 to the 3/4 and at least the base
>> address of the UART for the console changed. Getting it working should be a
>> combination of detective work to figure out what precisely changed and fix
>> it along with the possibility of the need for a different device driver on
>> the 3/4.
>>
>> FWIW I noticed that the RSB package qemu4 includes a simulator for the
>> pi2 although I haven't had a chance to see if it works with RTEMS. If it
>> does, that eliminates absolutely needing pi2 hardware.
>>
> Can someone provide instruction on the simulator, I searched a lot but
> found no help.
>
>>
>>
> Anyway, that's just one idea. It would be useful.
>>
>> Thanks.
>>
>> --joel
>>
>>
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.rtems.org/pipermail/devel/attachments/20191126/e34e420b/attachment-0001.html>