Public bug reported:

There is a regression preventing a user to upgrade from 5.4 kernel to anything 
that's higher than 5.5. When using such kernel the image orientation is wrong 
(rotated by 90°C). Also the kernel log contains:
wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: [drm] Unknown revid 0x06
wrz 15 09:19:49 desktop kernel: rtw_8821ce 0000:01:00.0: Firmware version 
24.8.0, H2C version 12
wrz 15 09:19:49 desktop kernel: Console: switching to colour dummy device 80x25
wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: vgaarb: deactivate vga 
console
wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: [drm] couldn't get memory 
information
wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: vgaarb: changed VGA decodes: 
olddecodes=io+mem,decodes=io+mem:o>
wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: [drm] Finished loading DMC 
firmware i915/glk_dmc_ver1_04.bin (v>
wrz 15 09:19:49 desktop kernel: 
================================================================================
wrz 15 09:19:49 desktop kernel: UBSAN: array-index-out-of-bounds in 
/build/linux-hwe-5.15-DZkSuT/linux-hwe-5.15-5.>
wrz 15 09:19:49 desktop kernel: index 5 is out of range for type 'u32 [5]'

(full stack trace attached)

The video hardware in use is:
00:02.0 VGA compatible controller [0300]: Intel Corporation UHD Graphics 605 
[8086:3185] (rev 06) (prog-if 00 [VGA controller])
(...)
Kernel driver in use: i915
Kernel modules: i915

The user wanted to upgrade from bionic to focal with HWE kernel (they
needed it due to some networking hardware they wanted to have supported
by the newer kernel).

The user was testing mainline stable kernels and noticed that the last
working kernel was the 5.4 series, while anything starting from 5.5 and
above is BROKEN (symptoms as described in the first paragraph above).

Together with the user we have run a bisection between v5.4 and v5.5 on the 
upstream stable kernel and we were able to identify the first broken commit to 
be:
8f4b1068e7fc3df1a77ac8151767e56b208cc87f drm/i915: Check some transcoder timing 
minimum limits

To confirm I have reverted this change on top of the HWE kernel for
focal and the user have confirmed that this resolved the issue (test
build available at ppa:dgadomski/kernel-sf368743).

I am not fully sure what the purpose of this patch was, but I assume the
regression was not intended and the hardware should be still supported.

Attaching lshw and lspci output.

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: se sts

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https://bugs.launchpad.net/bugs/2044131

Title:
  i915 regression introduced with 5.5 kernel

Status in linux package in Ubuntu:
  New

Bug description:
  There is a regression preventing a user to upgrade from 5.4 kernel to 
anything that's higher than 5.5. When using such kernel the image orientation 
is wrong (rotated by 90°C). Also the kernel log contains:
  wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: [drm] Unknown revid 0x06
  wrz 15 09:19:49 desktop kernel: rtw_8821ce 0000:01:00.0: Firmware version 
24.8.0, H2C version 12
  wrz 15 09:19:49 desktop kernel: Console: switching to colour dummy device 
80x25
  wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: vgaarb: deactivate vga 
console
  wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: [drm] couldn't get memory 
information
  wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: vgaarb: changed VGA 
decodes: olddecodes=io+mem,decodes=io+mem:o>
  wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: [drm] Finished loading DMC 
firmware i915/glk_dmc_ver1_04.bin (v>
  wrz 15 09:19:49 desktop kernel: 
================================================================================
  wrz 15 09:19:49 desktop kernel: UBSAN: array-index-out-of-bounds in 
/build/linux-hwe-5.15-DZkSuT/linux-hwe-5.15-5.>
  wrz 15 09:19:49 desktop kernel: index 5 is out of range for type 'u32 [5]'

  (full stack trace attached)

  The video hardware in use is:
  00:02.0 VGA compatible controller [0300]: Intel Corporation UHD Graphics 605 
[8086:3185] (rev 06) (prog-if 00 [VGA controller])
  (...)
  Kernel driver in use: i915
  Kernel modules: i915

  The user wanted to upgrade from bionic to focal with HWE kernel (they
  needed it due to some networking hardware they wanted to have
  supported by the newer kernel).

  The user was testing mainline stable kernels and noticed that the last
  working kernel was the 5.4 series, while anything starting from 5.5
  and above is BROKEN (symptoms as described in the first paragraph
  above).

  Together with the user we have run a bisection between v5.4 and v5.5 on the 
upstream stable kernel and we were able to identify the first broken commit to 
be:
  8f4b1068e7fc3df1a77ac8151767e56b208cc87f drm/i915: Check some transcoder 
timing minimum limits

  To confirm I have reverted this change on top of the HWE kernel for
  focal and the user have confirmed that this resolved the issue (test
  build available at ppa:dgadomski/kernel-sf368743).

  I am not fully sure what the purpose of this patch was, but I assume
  the regression was not intended and the hardware should be still
  supported.

  Attaching lshw and lspci output.

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