platform: add support for the rpi4b

[stapelberg]

The Raspberry Pi 4 was just released: https://www.raspberrypi.org/blog/raspberry-pi-4-on-sale-now-from-35/

I have ordered one to make sure gokrazy works on it.

Update: tracking issues that I have encountered on the Raspberry Pi 4 Model B (rpi4b):

• the UART swap dtb patch needs to be rebased onto the rpi4 dtb file
• the broadcom genet driver needs to be enabled for the eth0 network interface to show up
• The SD card reader currently ends up at /dev/mmcblk1*, but should be /dev/mmcblk0* for consistency with earlier models.
  • The Raspberry Pi kernel uses a kernel patch for mmc numbering based on devicetree aliases, but the patch has been declined for upstream inclusion.
  • Side note: this wouldn’t be a problem if we would use UUID= to specify the root device, but those require booting with an initrd, which is something I’d like to avoid for as long as possible.
  • We’re now using PARTUUID=, which is understood by the kernel and does not require an initrd: see issue Use PARTUUID= for identifying root device #52
• network interface: interface detected and link status shown as up, but device does not respond to IPv6 link-local pings or fetch an IP address via DHCPv4
  • EEPROM version “2019-09-10 - Git f626c772” contains the only ethernet change, but it might be relevant: “Configure ethernet RGMII pins at power on. This is a minor change which which may improve reliability of ethernet for some users.”.
  • In my tests, updating to the latest rpi-eeprom (git commit a5be2ff8b15dd36cb3bb83a3f864514cd9cfcf3e) helped a bit (the device picks an IPv6 address based on router advertisements), but I still can’t get ethernet to work.
  • posted Raspberry Pi 4: bcmgenet ethernet does not send packets with Linux 5.6.2 lategoodbye/rpi-zero#47
  • fixed by setting phy-mode to rgmii
• include Raspberry Pi 4 firmware files (start4*, fixup4*)
• USB ports don’t work
  • the xhci_hcd driver is enabled (CONFIG_USB_XHCI_HCD=y), but doesn’t enumerate any devices at boot
• set up an rpi4 in continuous integration
• include eeprom updates (gokrazy/rpi-eeprom for consistency? or just include in firmware?)
  • background info: https://news.ycombinator.com/item?id=21674550
  • set up GitHub actions CI to pull in new EEPROM versions
  • packer: ensure filenames match the updater pattern
  • display the eeprom version by reading pieeprom.sig and vl805.sig when RECOVERY.00* is present (= last update succeeded)
  • skip updates when the EEPROM is already up-to-date Update: I have verified that the bootloader skips EEPROM updates when the EEPROM is already up to date: https://user-images.githubusercontent.com/55506/85105058-10d47e80-b20a-11ea-8d13-5caa8ad961c3.jpg
• update issue template
• update website
• update README.md
• update gokr-packer message
• repo descriptions

[stapelberg]

We’re currently blocked on raspberrypi/linux#3032 (arm64 kernel support for the Pi 4 being in early stages).

Not sure which patches are required to make this work.

[stapelberg]

To summarize progress on the referenced issue: when manually placing the dtb file, armstub and raspberrypi/linux kernel image on the SD card, and limiting the memory to 1G, I can get some output on the serial console.

I can’t get an upstream kernel to print anything on the serial console, though.

I suppose it’ll be a while before the necessary changes are upstreamed.

Edit: Fedora is also waiting for upstream changes: https://lists.fedoraproject.org/archives/list/arm@lists.fedoraproject.org/thread/OFIGDPUDFOA3BB33GVCDHTSGZ2Q77APK/ (so is Debian)

[vianpl]

To summarize progress on the referenced issue: when manually placing the dtb file, armstub and raspberrypi/linux kernel image on the SD card, and limiting the memory to 1G, I can get some output on the serial console.

I can’t get an upstream kernel to print anything on the serial console, though.

I suppose it’ll be a while before the necessary changes are upstreamed.

Can you try adding gpu_freq=500 to config.txt? AFAIK the VPU clock and UART are derived from the same PLL and I suspect the firmware may be altering the frequencies behind your back.

[stapelberg]

Side note: dividuum described how to do firmware updates at https://news.ycombinator.com/item?id=21674550, which is important for better thermals and power usage: https://www.raspberrypi.org/blog/thermal-testing-raspberry-pi-4/

[stapelberg]

lategoodbye/rpi-zero#43 has a good overview of the current status. Looks like Linux 5.6 can be the earliest we could possibly see good-enough support.

[stapelberg]

The EEPROM updates are now in place, and I have been using a Pi 4 to develop and to run my home automation for weeks without any trouble.

Hence, the Pi 4 is now officially a target platform of https://gokrazy.org/!