Re: Screen update issue (drm/i915/fbc: enable FBC by default on HSW and BDW)

From: "Zanoni, Paulo R" <paulo.r.zanoni@intel.com>
To: "stevenhoneyman@gmail.com" <stevenhoneyman@gmail.com>,
	"daniel.vetter@ffwll.ch" <daniel.vetter@ffwll.ch>
Cc: "intel-gfx@lists.freedesktop.org" <intel-gfx@lists.freedesktop.org>
Subject: Re: Screen update issue (drm/i915/fbc: enable FBC by default on HSW and BDW)
Date: Thu, 9 Jun 2016 14:49:32 +0000	[thread overview]
Message-ID: <1465483772.3885.80.camel@intel.com> (raw)
In-Reply-To: <CABz95_A4s9TXTzr_ww3+H2o6Kg-2-tNsYootkKoShswfOuHXTA@mail.gmail.com>

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.

Anyway, I should submit a patch reverting FBC on stable Kernels.

Thanks,
Paulo

> 
> 
> Thanks,
> Steven
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