[Bug 101111] New: [Regression BDW] backlight flickering/display artifacting on Broadwell integrated graphics with 4.12-rc1

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101111

            Bug ID: 101111
           Summary: [Regression BDW] backlight flickering/display
                    artifacting on Broadwell integrated graphics with
                    4.12-rc1
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: critical
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: nicholas.stommel at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

As of 4.12-rc1, the following regression happens:
On a laptop with integrated Broadwell 5500U graphics, I am experiencing a
slight but noticeable and extremely annoying backlight flickering. This is
especially apparent when the screen brightness is adjusted high on dark grey
backgrounds where there is a noticeable sort of constant flickering/variation
in brightness of the background sometimes striated with thin lines but usually
just flickering slightly lighter or darker. Of course, this occurs at all
brightness levels, but is more obvious there. This problem has only been
present as of the release of 4.12-rc1, and is also present on drm-tip and
drm-intel-nightly. It seems related to the updates in the i915 Intel integrated
graphics module. It's problematic enough to be a fairly major annoyance on the
5500U Broadwell SoC.

The following is my system configuration. I can confirm that this problem
occurs even with the latest intel firmware/drivers in Ubuntu 17.04 as well as
on my primary system running Ubuntu 16.04.2 LTS, and that it does not happen on
4.11.x or previous kernels.

uname -a
Linux delphi 4.12.0-041200rc1-generic #201705131731 SMP Sat May 13 21:32:36 UTC
2017 x86_64 x86_64 x86_64 GNU/Linux

sudo lshw -short
H/W path       Device     Class          Description
====================================================
                          system         HP Spectre x360 Convertible (N5R94UA)
/0                        bus            802D
/0/0                      memory         64KiB BIOS
/0/10                     memory         32KiB L1 cache
/0/11                     memory         32KiB L1 cache
/0/12                     memory         256KiB L2 cache
/0/13                     memory         4MiB L3 cache
/0/14                     processor      Intel(R) Core(TM) i7-5500U CPU @
2.40GH
/0/16                     memory         8GiB System Memory
/0/16/0                   memory         4GiB Row of chips Synchronous 1600 MHz 
/0/16/1                   memory         4GiB Row of chips Synchronous 1600 MHz 
/0/100                    bridge         Broadwell-U Host Bridge -OPI
/0/100/2                  display        Broadwell-U Integrated Graphics
/0/100/3                  multimedia     Broadwell-U Audio Controller
/0/100/14                 bus            Wildcat Point-LP USB xHCI Controller
/0/100/14/0    usb1       bus            xHCI Host Controller
/0/100/14/0/1             input          USB Receiver
/0/100/14/0/3             multimedia     HP Truevision Full HD
/0/100/14/0/4             input          Touchscreen
/0/100/14/0/5             input          ITE Device(8350)
/0/100/14/0/7             communication  Bluetooth wireless interface
/0/100/14/1    usb2       bus            xHCI Host Controller
/0/100/16                 communication  Wildcat Point-LP MEI Controller #1
/0/100/1c                 bridge         Wildcat Point-LP PCI Express Root Port 
/0/100/1c/0               generic        RTS5227 PCI Express Card Reader
/0/100/1c.2               bridge         Wildcat Point-LP PCI Express Root Port 
/0/100/1c.2/0  wlo1       network        Wireless 7265
/0/100/1f                 bridge         Wildcat Point-LP LPC Controller
/0/100/1f.2               storage        Wildcat Point-LP SATA Controller [AHCI 
/0/100/1f.3               bus            Wildcat Point-LP SMBus Controller
/0/1           scsi0      storage        
/0/1/0.0.0     /dev/sda   disk           512GB SAMSUNG MZNTE512
/0/1/0.0.0/1   /dev/sda1  volume         449MiB Windows NTFS volume
/0/1/0.0.0/2   /dev/sda2  volume         99MiB Windows FAT volume
/0/1/0.0.0/3   /dev/sda3  volume         15MiB reserved partition
/0/1/0.0.0/4   /dev/sda4  volume         15EiB Windows FAT volume
/0/1/0.0.0/5   /dev/sda5  volume         838MiB Windows NTFS volume
/0/1/0.0.0/6   /dev/sda6  volume         146GiB Windows NTFS volume
/0/1/0.0.0/7   /dev/sda7  volume         89GiB EXT4 volume
/0/1/0.0.0/8   /dev/sda8  volume         8099MiB Linux swap volume
/1                        power          PK03056XL

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