Comment 26 for bug 1848703

I have a PI 4 (4GB)

I loaded and installed the arm64 eoan
USB didn't work, ssh did

I set total_mem=1024
USB worked

I set total_mem=3072
USB failed

I set total_mem=1024 and loaded the linux image:
wget https://people.canonical.com/~hwang4/rpiv2/arm64/linux-image-5.3.0-1008-raspi2_5.3.0-1008.9+newupdate_arm64.deb
wget https://people.canonical.com/~hwang4/rpiv2/arm64/linux-modules-5.3.0-1008-raspi2_5.3.0-1008.9+newupdate_arm64.deb

sudo dpkg -i linux-modules-5.3.0-1008-raspi2_5.3.0-1008.9+newupdate_arm64.deb
sudo dpkg -i linux-image-5.3.0-1008-raspi2_5.3.0-1008.9+newupdate_arm64.deb
sudo reboot

USB Worked

I commented out the total_mem=3072
USB failed

I believe the following will help:

In the raspberry pi git (4.19.y)
https://github.com/raspberrypi/linux/issues/3093

hitmoon commented on 12 Aug
    "I've created a trivial patch to add bounce buffers on ARM64 for pcie-bcrmstb.
    pcie-brcmstb-bounce64.patch.zip

    I tried this patch, it works for me!
    All 4G memory is alive now, COOL !! :-)
    Thanks @yaroslavros !

This fixed my linux image for my home rolled 19.04 ubuntu so I hope it fixes yours