Thx Alex, that allowed me to fill the gaps and I have consolidated the
SRU Justification and added it to the bug description.

** Description changed:

  SRU Justification:
  ==================
  
  [Impact]
  
  * Since older firmware may not support the uplink state setting, this
  can lead to problems.
  
  * Now expose firmware indication that it supports setting eswitch uplink
  state to follow the physical link.
  
  * If a kernel without the backport is used on an adapter which does not
  have the latest adapter firmware, the adapter silently drops outgoing
  traffic.
  
  * This is a regression which was introduced with kernel 5.4.0-48.
  
  [Fix]
  
  * upstream fix (as in 5.11):
-   9c9be85f6b59d80efe4705109c0396df18d4e11d 9c9be85f6b59 "net/mlx5e: Add 
missing capability check for uplink follow"
+   9c9be85f6b59d80efe4705109c0396df18d4e11d 9c9be85f6b59 "net/mlx5e: Add 
missing capability check for uplink follow"
  
  * backport for focal: https://launchpadlibrarian.net/529543695/0001
  -Backport-net-mlx5e-Add-missing-capability-check-for-.patch
  
  * backport for groovy: https://launchpadlibrarian.net/529775887/0001
  -Backport-groovy-net-mlx5e-Add-missing-capability-che.patch
  
  [Test Case]
  
- * It requires an IBM Z or LinuxONE system, with groovy/focal installed
- in LPAR   and RoCE Express 2.x adapters attached.
+ * Two IBM Z or LinuxONE systems, installed with Ubuntu Server 20.04 or
+ 20.10 on LPAR, are needed.
  
- * ...
+ * Each with RoCE Express 2.x adapters (Mellanox ConnectX4/5) attached
+ and firmware 16.29.1006 or earlier.
+ 
+ * Assign an IP address to the adapters on both systems and try to ping
+ one node from the other.
+ 
+ * The ping will just fail with the stock Ubuntu kernels (not having the
+ patch), but will succeed with kernels that incl. the patches (like the
+ test builds from the PPA mentioned below).
  
  * Due to the lack of hardware this needs to be verified by IBM.
  
  [Regression Potential]
  
  * Undesired / erroneous behavior in case the modified if condition is
  assembled in a wrong way.
  
  * Again wrong behavior in case the modification of the capability bits
  in mlx5_ifc_cmd_hca_cap_bits are wrong.
  
  * All modification are limited to the mlx5 driver only.
  
  * The changes are relatively limited with effectively two lines removed
  and 4 added (three of them adjustments of the capability bits only).
  
  * The modifications were done and tested by IBM and reviewed by Mellanox
  (see LP comments),   based on a PPA test build.
  
  [Other]
  
  * The above patch/commit was upstream accepted with kernel 5.11.
  
  * Hence the patch is not needed for hirsute, just needs to be SRUed for
  groovy and focal.
  
  * The commit couldn't be cleanly cherry-picked, mainly due to changed
  context, hence the backport(s).
  
  __________
  
  Expose firmware indication that it supports setting eswitch uplink state
  to follow (follow the physical link). Condition setting the eswitch
  uplink admin-state with this capability bit. Older FW may not support
  the uplink state setting.
  
  Available fix with kernel 5.11.
  
https://github.com/torvalds/linux/commit/9c9be85f6b59d80efe4705109c0396df18d4e11d
  
  Now required for Ubuntu 20.04 via backport patch.

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https://bugs.launchpad.net/bugs/1921104

Title:
  net/mlx5e: Add missing capability check for uplink follow  for Ubuntu
  20.04

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