** Patch added: 
"0001-UBUNT-SAUCE-arm64-dtbs-Add-symbols-when-compiling-dt.patch"
   
https://bugs.launchpad.net/ubuntu/+source/linux-raspi2/+bug/1782121/+attachment/5164457/+files/0001-UBUNT-SAUCE-arm64-dtbs-Add-symbols-when-compiling-dt.patch

** Description changed:

  Impact:
  
  Overlay dtb files should be applied to the main board dtb, before it's
  being passed down to the kernel for boot - but this didn't happen in the
  arm64 variant of the bionic/raspi2 kernel.
  
  /boot/firmware/config.txt:
  ...
  dtoverlay=pitft35-resistive
- 
  
  /boot/firmware/cmdline.txt:
  dwc_otg.lpm_enable=0 console=serial0,115200 console=tty1 root=/dev/mmcblk0p2 
rootfstype=ext4 elevator=deadline rootwait fbcon=map:10 fbcon=font:VGA8x8
  
  But the attached second display is never initialized.
  
  Fix:
  
  The main dtb must be built with symbols, to let overlay files find which
  section to patch - the applied patch does exactly that.
  
  Apply, build, install and reboot:
  
  dmesg:
  ...
- [    5.144664] fbtft: module is from the staging directory, the quality is 
unknown, you have been warned.
- [    5.145814] fbtft: module verification failed: signature and/or required 
key missing - tainting kernel
  [    5.157547] fb_hx8357d: module is from the staging directory, the quality 
is unknown, you have been warned.
  [    5.158349] fbtft_of_value: buswidth = 8
  [    5.158362] fbtft_of_value: debug = 0
  [    5.158366] fbtft_of_value: rotate = 90
  [    5.158372] fbtft_of_value: fps = 25
  
- ubuntu@raspi64:~$ ls -la /dev/fb1 
+ ubuntu@raspi64:~$ ls -la /dev/fb1
  crw-rw---- 1 root video 29, 1 Jan 28 15:58 /dev/fb1
- 
  
  Regression risk:
  
  We only change how the arm64 raspi2 dtbs are generated, and since we
  didn't produce any image using this kernel so far, the regression risk
  is zero.
  
  ---

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https://bugs.launchpad.net/bugs/1782121

Title:
  arm64: overlays don't get applied

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