[Arm-dev] Why RPi3 under Arm32 rather than AArch64?

[Johnny Hughes]

On 01/04/2018 04:30 PM, Gordan Bobic wrote:
> Things required to "support" Pi3 aarch64 that aren't already in place in
> core CentOS (or at least I haven't managed to find them):
> 
> 1) Pi3 firmware blobs
> Trivially downloadable from
> https://github.com/raspberrypi/firmware/tree/master/boot

I assume we include those in our armhfp kernel so this is not a problem
for an official CentOS image.

> 
> 2) UEFI bootloader
> There are two options, u-boot and Tianocore.
> My current Pi3 aarch64 image works with u-boot that I grabbed from the
> Fedora 26 image. 
> I'm currently trying to get it working with Tianocore from here:
> https://github.com/andreiw/RaspberryPiPkg
> I _almost_ have it working (gets as far as booting grub, but grub then
> doesn't manage to boot up the kernel, almost certainly a dtb issue
> somewhere).

We kind of need to be able to BUILD this, not just take it from
something else an use it.  At least that is certainly preferable. I
suppose we can just include it as a SOURCE for the SRPM, but that is not
ideal.

> 
> 3) Kernel
> I keep my own mainline kernel build for aarch64, loosely based on, IIRC,
> 4.5.x that shipped with CentOS aarch64, but with some modifications. I
> have a build that works on both my X-Gene and the Pi3. You can find it here:
> http://ftp.redsleeve.org/pub/misc/kernel/aarch64/RPMS/
> (Note: I only included Pi 3 SoC configuration as of 4.9.73).
> 
> So it's not exactly an insurmountable problem, it's just a case off
> dropping a tarball of 5-6 files onto the /boot/efi FAT partition, having
> the appropriate kernel installed in the image, and it should "just work".
> I can have a working image with u-boot EFI as soon as I find half an
> hour to spare.
> The one with Tianocore EFI will take a little longer.
> 

Is there something about OUR generic CentOS 4.9.x kernel SRPM that does
not work if compiled on aarch64:

http://vault.centos.org/altarch/7.4.1708/experimental/Source/i386/Source/SPackages/

That SRPM is what we use for i386/x86_64 and the generic armhfp kernel.
If we need a new config file, we can likely figure that out.

We would obviously need to add in whatever is necessary for the firmware
blobs and the pi uboot config, etc.

I am not opposed to doing this if we can do it right .. which is that it
is secure and reproducible to build and install via the RPMs (the
kernel), which are produced completely produce automatically from the
SRPM .. AND for the image, it is completely buildable via a kickstart
file or one of the normal tools and everything does not have to be hand
added, etc.  If we can make that happen, then I am happy for us to have
an aarch64 build.

But, it is odd that the RPI foundation doesn't care enough to make that
happen.

We might get some ideas from the SRPMS these guys do:

https://www.linux.com/news/learn/intro-to-linux/first-64-bit-and-enterprise-os-comes-raspberry-pi-3

(if we can see them)

Thanks,
Johnny Hughes

> 
> 
> On Thu, Jan 4, 2018 at 9:55 PM, Fabian Arrotin <arrfab at centos.org
> <mailto:arrfab at centos.org>> wrote:
> 
>     On 04/01/18 19:26, Christopher Ursich wrote:
>     > Hi, all.  First-timer here.
>     >
>     > I am setting up a new Raspberry Pi 3.  When I review the AltArch
>     pages,
>     > I see that most of the RPi3 coverage is categorized under Arm32,
>     including
>     >
>     >
>       https://wiki.centos.org/SpecialInterestGroup/AltArch/Arm32/RaspberryPi3
>     <https://wiki.centos.org/SpecialInterestGroup/AltArch/Arm32/RaspberryPi3>
> 
>     Because we targeted armhfp even for the Pi3 initially, as even the Pi
>     Foundation had no plan to provide/build at the beginning aarch64
>     kernel/code for the pi3
>     TBH (my own opinion) it doesn't even really make sense to use aarch64
>     code on the pi3 itself with such low specs .. only benefit is probably
>     that epel exists for aarch64 vs armhfp and also same tree if you want to
>     deploy to "real" aarch64 nodes in Datacenter ...
> 
>     Now, I'll let Jim (the aarch64 maintainer) explain his plans for aarch64
>     tree for pi3, but at this stage of meltdown and spectre, I guess we all
>     have other urgent things to do too :-)

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