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[Po-Hsu Lin <po-hsu.lin@xxxxxxxxxxxxx>]

201408-15387 Dell Latitude E7250, a Broadwell-U UMA system [8086:1616]
With kittyhawk 2.0 image (3.19.0-26 #27), I can reproduce the following issues:
1. Normal <-> 180 display rotation, it would cause black screen.
2. VT switch, the screen will flick and the *ERROR* message could be found in dmesg
3. Resume from S3, you can see the screen before suspend, and GPU hang error message could be found in dmesg

However, I can't 100% reproduce the HDMI hot plug issue. Only 1 out of
10.

Test result:
With the kernel provided in #4 (tested with 3.19.0-26-generic_3.19.0-26.27+bpo0.2_amd64), all these issues are gone (HDMI hot plug works as expected too).
But:
* Call trace for i915_bpo could be found on boot in dmesg output
* Call trace for i915_bpo could be found after connecting the HDMI cable
* Call trace for i915_bpo could be found after connecting the DP cable
* HDMI audio and DP audio are not working

Please find the attachment for the detailed logs.

For more information about the test cases, please refer to this private test report:
https://certification.canonical.com/hardware/201408-15387/submission/105457/

** Attachment added: "dmesg-201408-15387.zip"
   https://bugs.launchpad.net/ubuntu/vivid/+source/linux/+bug/1483320/+attachment/4443175/+files/dmesg-201408-15387.zip

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https://bugs.launchpad.net/bugs/1483320

Title:
  Migrate Broadwell to use i915_bpo

Status in linux package in Ubuntu:
  Invalid
Status in linux source package in Vivid:
  In Progress

Bug description:
  There are several bugs affecting Broadwell generation graphics in the
  vivid kernel (3.19), but not found in 4.2rc which i915_bpo module is
  based on. In order to support our OEM partners (and other BDW users)
  it would make sense to migrate BDW to use i915_bpo instead.

  The known (public) bugs this would fix are:

  - screen is black after xrandr rotate command
  https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1446979

  - changing the VT causes flicker
  https://bugs.freedesktop.org/show_bug.cgi?id=85583
  https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1450557

  - GPU hangs on resume
  https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1468232
  (and dupes, which I believe there are several of)

  - and some OEM machines can't always hotplug the HDMI output (no
  public bug AIUI)

  the migration should not be too risky, since i915_bpo is already used
  for Braswell which is same generation as (=based on) BDW.

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