[Intel-gfx] Possible 4.5 i915 Skylake regression

[Andy Lutomirski]

On Tue, Feb 16, 2016 at 8:12 AM, Daniel Vetter <daniel at ffwll.ch> wrote:
> On Mon, Feb 15, 2016 at 06:58:33AM -0800, Andy Lutomirski wrote:
>> On Sun, Feb 14, 2016 at 6:59 PM, Andy Lutomirski <luto at kernel.org> wrote:
>> > Hi-
>> >
>> > On 4.5-rc3 on a Dell XPS 13 9350 (Skylake i915, no nvidia on this
>> > model), shortly after resume, I saw a single black flash on the
>> > screen.  The log said:
>> >
>> > [Feb13 07:05] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR*
>> > CPU pipe A FIFO underrun
>> >
>> > I haven't seen this on 4.4.
>> >
>> > I'd be happy to dig up debugging info, but I don't know what would be
>> > useful.  I have no i915 module options set.
>>
>> It's flashing quite frequently now, although I seem to get the
>> underrun warning only once per resume.
>
> We shut up the warning irq source to avoid hijacking an entire cpu core
> ;-)
>
> There's a fix from Matt right after 4.5-rc4 in Linus' branch. I'm hoping
> that should help.

Do you mean:

commit e2e407dc093f530b771ee8bf8fe1be41e3cea8b3
Author: Matt Roper <matthew.d.roper at intel.com>
Date:   Mon Feb 8 11:05:28 2016 -0800

    drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)

If so, it didn't help.  I'm currently doing a full rebuild just in
case I messed something up, though.

--Andy