Raspberry Pi 2 Model B Rev 1.2 only sees 1 CPU with 64bit kernel

[digitallyelite]

Describe the bug
Upon boot, only 1 CPU is available for use.

To reproduce
Install 64bit kernel on a Raspberry Pi 2 Model B Rev 1.2

Expected behaviour
All 4 CPUs should be available

Actual behaviour
Only 1 CPU is available (32bit kernel does not have this issue)

• Which model of Raspberry Pi? e.g. Pi3B+, PiZeroW
  RaspberryPi2 v1.2
• Which OS and version (cat /etc/rpi-issue)?
  Raspbian Buster
• Which firmware version (vcgencmd version)?
  Sep 12 2019 16:32:35
  Copyright (c) 2012 Broadcom
  version 4b30e8dcf91177a0be822c4c8d3bac8ed65f7ea5 (clean) (release) (start)
• Which kernel version (uname -a)?
  4.19.71
  Logs
  dmesg | grep cpu spits out the following that I think is pertinent...
  [0.000000] /cpus/cpu@1: missing enable-method property
  [0.000000] /cpus/cpu@2: missing enable-method property
  [0.000000] /cpus/cpu@3: missing enable-method property

Additional context
Both 32bit and 64bit /proc/cpuinfo list
Hardware: 2835
Revision: a02042
Model: Raspberry Pi 2 Model B Rev 1.2

Also, according to https://www.raspberrypi.org/documentation/hardware/raspberrypi/revision-codes/README.md it seems the revision code should be a22042 and does not list a02042

[popcornmix]

Complete output of uname -a would have been useful.
Is this rpi-update kernel with arm_64bit=1, or a kernel you've built yourself?

[pelwell]

The reason will be that Pi 2B didn't used to be a 64-bit device, but the rev 1.2 iteration comes with at 2837. The Device Tree for the 2B hasn't changed, hence the lack of enable-methods. The correct solution would be to introduce bcm2710-rpi-2-b.dtb, but it would require changes to the kernel and firmware repos.

[digitallyelite]

@popcornmix it happened with both a self built as well as rpi-update with arm_64bit=1

full uname -a is
Linux raspberrypi 4.19.71-v8+ #1263 SMP PREEMPT Thu Sep 12 16:28:48 BST 2019 aarch64 GNU/Linux

@pelwell i'm assuming that that work is very low on the totem pole/won't be done at all? I could probably mash together a dts file, but if the firmware never recognizes it (Which revision is incorrect, the matrix at the revision-codes URL above, or the one on the board?) would it even be worth doing?

[pelwell]

You can force the firmware to use any DTB using the device_tree=whatever.dtb setting in config. txt. I was referring to the automatic file selection based on revision codes. If you can hack together and share a working dts it will make it much more likely the rest of the work will get done.

[pelwell]

PR #3235 shouldn't be too far wrong.

[pelwell]

A small patch has been dropped into the firmware mill and may pop out of the other side in the next few days.

[pelwell]

The latest firmware (available from rpi-update) should attempt to load bcm2710-rpi-2-b.dtb on a rev 1.2 Pi 2, falling back to bcm2709-rpi-2-b.dtb if it isn't found.

[digitallyelite]

Just tested the firmware here and it does seem to be working as intended, 2710 if it exists, and 2709 if it does not. I haven't noticed anything super out of the ordinary on booting it 64bit - it sees all 1GB of ram, rng tools seems to be starting, kernel uname is
Linux raspberrypi 4.19.73-v8+ #1266 SMP PREEMPT Tue Sep 17 21:08:24 BST 2019 aarch64 GNU/Linux

The only thing out of the ordinary to me, is that it still reports a revision of a02042 instead of a22042 - unless I have one from Sony UK and not Embest and it just hasn't been added to the matrix yet?

[pelwell]

If the board has a small QR code sticker on the bottom then it's built by Sony.

[digitallyelite]

There is a very tiny one, with what could be a QR code and a "19/05" on it so I guess Sony UK are doing them and it's just not on the matrix yet :)

[pelwell]

Yes, that's the one.

Where is this matrix you keep referring to?

[digitallyelite]

Where is this matrix you keep referring to?
https://www.raspberrypi.org/documentation/hardware/raspberrypi/revision-codes/README.md

Or maybe better, should I send a PR to https://github.com/raspberrypi/documentation/blob/master/hardware/raspberrypi/revision-codes/README.md to add the Sony UK revision?

[pelwell]

Or maybe better, should I send a PR

Yes - go for it. I'd merge it myself if I had the privileges on that repo.

[digitallyelite]

Done, thank you so much for the work to get 64bit support in for the RaspberryPi2 v1.2, it's greatly appreciated!

[digitallyelite]

Actually... something isn't quite right, but I don't think it's specific to these changes. Basically, all of my testing happened on the minimal Buster image, which is console only. But if I enable 64bit (with or without the dtb, which is why I believe this issue isn't specific to these changes) all I get is a blank screen, but it won't let me even switch to a console. X just seems to complain about a missing g2d_23 driver not found in /lib/modules/4.19.73-v8+ (??) and then there's an undefined symbol in fbturbo_drv.so... is this something I should take to the forums?

[pelwell]

Do you have "dtoverlay=vc4-fkms-v3d" in config.txt?

[digitallyelite]

Only in the [pi4] section

[pelwell]

I suggest trying it, at least as a workaround.

[digitallyelite]

that worked, thanks for the help. Since the dts is in now, I believe we can close this issue?

[pelwell]

I won't deny you the pleasure.