[Intel-gfx] Screen update issue (drm/i915/fbc: enable FBC by default on HSW and BDW)

[Steven Honeyman]

On 9 June 2016 at 15:49, Zanoni, Paulo R <paulo.r.zanoni at intel.com> wrote:
> Em Qua, 2016-06-08 às 22:35 +0100, Steven Honeyman escreveu:
>> Hi,
>
> Hi
>
> CC'ing the mailing list.
>
>>
>> With commit a98ee79317b4091cafb502b4ffdbbbe1335e298c to enable FBC by
>> default, I get a strange issue with screen update/refresh (sorry if
>> my
>> terminology is off - I'm not a graphics dev!).
>> Here's how it went (all in the past few hours):
>>
>> Kernel 4.5.5 (before the patch) - everything OK.
>> Kernel 4.6.2 - In a terminal window (openbox+roxterm or tilda, if
>> that
>> matters), the screen only updated approx 1 or 2 times per second when
>> typing (e.g. hold a key and they appear in chunks of 15-20!). Holding
>> a key and moving the mouse, appears fine.
>> Kernel 4.6.1 - (same as 4.6.2, but I had to try)
>> Kernel 4.7-rc2 - Same refresh/update problem, but this time moving
>> the
>> mouse had no effect.
>> Spent 5 mins googling, found your patch, applied i915.enable_fbc=0
>> and
>> 4.7-rc2 behaves as it should.
>>
>> So in response to your suggestions for debugging this made in the
>> commit message, I swapped out the boot parameter for drm.debug=0xe,
>> but apart from the stuff at startup I got nothing extra after
>> reproducing the problem.
>> Your suggestions make it sound like you might expect something
>> 'major'
>> to go wrong, infrequently... however this is always apparent, and
>> (fairly) minor.
>>
>> Hardware is a Dell E6540, Haswell i5 with Intel graphics. FHD eDP
>> panel + external FHD DVI screen.
>> Please let me know if there's any other info you want.
>
> Please boot with i915.enable_fbc=1 drm.debug=0xe, reproduce the problem
> and check if there is any dmesg line mentioning "FIFO underruns".
>
> Also, which distro version are you using? Are you using xf86-video-
> intel? Maybe also grab /var/log/Xorg.0.log.
>
> Perhaps it would be better if you open a bug on bugs.freedesktop.org,
> attach the relevant information, and provide me the link to the bug
> report. It's better to track bugs there.

Thanks - done: https://bugs.freedesktop.org/show_bug.cgi?id=96464

>
> Anyway, I should submit a patch reverting FBC on stable Kernels.
>
> Thanks,
> Paulo
>
>>
>>
>> Thanks,
>> Steven