[Bug 109248] New: [CFL] FIFO underruns on a hybrid machine but only while on "performance" (dGPU) mode

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=109248

            Bug ID: 109248
           Summary: [CFL] FIFO underruns on a hybrid machine but only
                    while on "performance" (dGPU) mode
           Product: DRI
           Version: XOrg git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: tjaalton at ubuntu.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Hi

Dell Inspiron 7580 hybrid laptop has issues with external monitors when on
"performance" (dGPU) mode; the external screen will start blinking and dmesg
has lots of: 

[492.008927] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe
A FIFO underrun
[492.009818] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe
B FIFO underrun

I don't have full logs right now, but at least 4.20 is still affected.
Everything newer would need a patched nvidia dkms and that hasn't been tried
yet..


when it's running on iGPU everything is fine AIUI

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