Public bug reported:

[Impact]
Another bug was found in the pl011/spcr code that implements the work-around 
for erratum E44. This erratum affects QDF2400 v1.1 silicon. The software bug is 
only exposed when using Firmware 2.0 or later (estimated release October 2017).

To ensure compatibility with future firmware, the Ubuntu kernel should
apply the aforementioned patch. Without this patch, customers using the
2.0 firmware and 1.1 silicon might not have a functional UART console,
either sometimes or always.

It is expected that this problem does not occur with 2.0 or later
silicon.

[Test Case]
Upgrade firmware to v2.0 on a QDF2400 server with 1.1 silicon, and the kernel 
should fail to boot, with the patch applied, we should see no boot failure.

[Fix]
Following patch in linux-next fixes this issue:
37ef38f3f838 tty: pl011: fix initialization order of QDF2400 E44

[Regression Potential]
This is a bug fix to tty driver and limited to qdf2400. Low risk.

** Affects: linux (Ubuntu)
     Importance: Critical
     Assignee: Manoj Iyer (manjo)
         Status: Triaged


** Tags: qdf2400

** Summary changed:

- [SRU][Zesty] pl011 E44 erratum patch needed for 2.0 firmware and 1.1 silicon
+ [SRU][Zesty] [QDF2400] pl011 E44 erratum patch needed for 2.0 firmware and 
1.1 silicon

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https://bugs.launchpad.net/bugs/1709123

Title:
  [SRU][Zesty] [QDF2400] pl011 E44 erratum patch needed for 2.0 firmware
  and 1.1 silicon

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