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The Raspberry Pi 4 has been out for a few months and already the community has got everything working in 64 bit mode.
Curious users need to be familiar with the use of a cross toolchain or have access to another armv8a system to build a 64 bit kernel for the Pi 4.
Analogue Video Output Analogue Audio Output Camera Screen
I don't have hardware to test the camera or screen.
Follow the method described in Raspberry Pi 3 64 bit Install
The Pi 4 differs in the kernel build, the /boot/config.txt content and the requirement for some code from raspberrypi/tools
Get the aarch64-unknown-linux-gnu cross toolchain.
To cross compile the kernel, start with
ARCH=arm64 CROSS_COMPILE=aarch64-unknown-linux-gnu- make bcm2711_defconfig
Check the other kernel configuration settings given in configure the kernel.
The Pi 4 USB 3 supports USB Attached SCSI (CONFIG_USB_UAS). Unlike bulk mode, it allows commands to USB storage devices to be overlapped. Enable USB Attached SCSI in the kernel if a USB3 storage device will be used.
The default CPU governor (CPU_FREQ_DEFAULT_GOV) is powersave. This runs the CRU at 600MHz all he time. CPU governors can be controlled in /proc or the default CPU governor can be changed to be ondemand.
Power Over Ethernet requires a .dto file to be loaded as well as kernel support.
The 4G RAM Pi 4 can build the 64 bit kernel in about an hour but a 64 bit toolchain is required, so the very first kernel cannot be built natively on the Pi.
Build and install the kernel, device tree and kernel modules an described in install the kernel binary, install the device tree, now named bcm2711-rpi-4-b.dtb and install the kernel modules.
The following is a bare minimum /boot/config.txt
# set 64 bit mode arm_64bit=1enable_gic=1 armstub=armstub8-gic.bin
# have a properly sized image disable_overscan=1 # for sound over HDMI hdmi_drive=2 # Enable audio (loads snd_bcm2835) dtparam=audio=on
may or may not be useful and are unchanged from earlier versions of the Raspberry Pi.
Rasberrypi/tools provides armstub8-gic.bin which must be copied to /boot
Naturally, its in a git repo. Clone it beside the Pi Sources and Pi Firmware repos.
git clone https://github.com/raspberrypi/tools
build the contents of tools/armstubs
make CC8=aarch64-unknown-linux-gnu-gcc LD8=aarch64-unknown-linux-gnu-ld OBJCOPY8=aarch64-unknown-linux-gnu-objcopy OBJDUMP8=aarch64-unknown-linux-gnu-objdump armstub8-gic.bin
cp armstub8-gic.bin /mnt/gentoo/boot/
The microSD interface supports the trim command.
Pi4_~arm64 ~ # fstrim -av /boot: 7.7 GiB (8250073088 bytes) trimmed on /dev/mmcblk0p1
If you have a suitable microSD card, consider adding fstrim to a weekly or monthly cron job.
The USB3 interface appears to support the kernels UAS (USB Attached SCSI) option. Its harmless to enable. Unfortunately, my USB3 to SATA cable does not work with UAS. Enable it in the kernel as its harmless.
Search for USB_UAS
<*> USB Attached SCSI
WiFi needs three firmware files in /lib/firmware/brcm/
brcmfmac43455-sdio.bin brcmfmac43455-sdio.clm_blob brcmfmac43455-sdio.txt
Which is almost but not quite the same as the Pi3. The catch is in brcmfmac43455-sdio.txt where grep boardflags3 produces different results for the Pi3 and Pi4 files.
The Pi4 version returns boardflags3=0x44200100 The Pi3 version returns boardflags3=0x48200100
With the wrong brcmfmac43455-sdio.txt file, bluetooth works but not WiFi.
The Pi4 has firmware. It no longer uses bootcode.bin, even if its present.
Be sure to keep your firmware up to date. New features are promised and optimisations like Power Reduction are already available.
There is a small trap for the unwary. The firmware updater program as distributed is an arm 32 bit program. The good news is that Sakakis genpi64 overlay has all the bits required to build an arm64 version in the normal Gentoo fashion.
# Required to update Pi4 firmware. media-libs/raspberrypi-userland::genpi64 dev-embedded/rpi4-eeprom-images::genpi64 dev-embedded/rpi4-eeprom-updater::genpi64
The Pi3b PoE HAT will power the P4 and a USB SSD.
Fan control works.
CFLAGS="-march=armv8-a+crc+simd -mtune=cortex-a72 -ftree-vectorize -O2 -pipe -fomit-frame-pointer"
-mtune=cortex-a72. Cortex-A72 mandatorily supports
+simd. But no crypto extension on BCM2835/RPi4. Adding
-fomit-frame-pointer to utilize more registers.
gcc-6.x allows the use of
-march=native but that will prevent the use of distcc. The above is the same as gcc-6.3 would set for
sakakis topic on the Raspberry Pi forums
All the contributors to issue 3032 on the Raspberry Pi github repo