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From: Hugh Dickins <hughd@google.com>
To: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>,
	Mario Kleiner <mario.kleiner@tuebingen.mpg.de>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/i915: Suppress spurious vblank interrupts
Date: Tue, 1 Feb 2011 10:46:17 -0800	[thread overview]
Message-ID: <AANLkTim4kL9OjBDiQQ1MBfOCzThxmDonBic11N45NKxj@mail.gmail.com> (raw)
In-Reply-To: <20110201100833.3219687e@jbarnes-desktop>

On Tue, Feb 1, 2011 at 10:08 AM, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
> On Tue, 1 Feb 2011 09:46:43 -0800
> Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
>>
>> Are you still seeing underruns during normal activity?

Yes.  That is, I see the "pipe a underrun" messages when I set drm
debug 7: I'm unaware of any ill-effect from them, unless they are
indeed a factor in my unflushed text issue.

>> I wonder if the
>> ones you were seeing before were only reported at 60Hz due to vblank
>> interrupt processing.  If we failed to clear the underrun status, we'd
>> report one every time we got a vblank interrupt (since the underruns
>> don't report interrupts by themselves).

I was surprised that i915_driver_irq_handler  "Clear the PIPE(A|B)STAT
regs" writes back precisely the pipea_stats it reads in, I'd have
expected to clear something there (and did earlier experiment with
writing back 0: black screen at boot!).  But assumed the protocol is
such that it acknowledges the status bits by writing same back.

>>
>> If so, that may just be a red herring in this case.
>
> More random questions arise from the info provided:
>  - why are we ending up in the flip code at all?  fvwm shouldn't
>   trigger that path...

Right.  I haven't double-checked the logic, but I believe it's because
of bits set in the underrunning pipea_stats.  I did one time modify
the underrun message to print out pipea_stats, over five seconds most
(265) values were 0x80440207
(there were also 14 occurrences of 0x80440007, 5 of 0x80440004 and 3
of 0x80440204).

>  - what's with all the underruns?  it looks like we *do* ack those
>   flags as needed, so apparently they're valid, but they indicate a
>   serious problem with the display pipeline; maybe self-refresh
>   shouldn't be enabled on your system (that would increase memory
>   latency and potentially cause underruns), running with
>   i915.powersave=0 would disable that feature

I just tried i915.powersave=0 but the underruns still appeared.  I
then tried earlier kernels, and was surprised to find no underruns
with 2.6.34, 2.6.36: the underruns appeared with 2.6.37.

>
> The lack of text really does sound like a render cache flushing
> problem, but the other issues are worrying as well, and could be
> compounding things.  And the last time I saw the issue, it was related
> to compositing and required an X server fix.  But supposedly you're not
> using compositing, so...

That's right.

Hugh

  reply	other threads:[~2011-02-01 18:46 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-12-20 18:12 [BISECTED] agp/intel: revert "Remove confusion of stolen entries not stolen memory" Arnd Bergmann
2010-12-20 18:53 ` Chris Wilson
2010-12-20 19:47   ` Arnd Bergmann
2010-12-20 19:52     ` Chris Wilson
2010-12-20 20:52       ` Arnd Bergmann
2010-12-20 21:06         ` Chris Wilson
2010-12-20 21:54           ` Arnd Bergmann
2010-12-20 22:08             ` Dave Airlie
2011-01-20 23:24           ` Frederic Weisbecker
2011-01-21 10:58             ` [PATCH] drm/i915,agp/intel: Do not clear stolen entries Chris Wilson
2011-01-21 16:26               ` Jiri Olsa
2011-01-23  1:12               ` Frederic Weisbecker
2011-01-23 11:01                 ` Chris Wilson
2011-01-23 17:59                   ` Frederic Weisbecker
2011-01-24  7:40                     ` Hugh Dickins
2011-01-24 10:10                       ` Chris Wilson
2011-01-26 21:39                         ` Arnd Bergmann
2011-01-28 22:00                         ` Hugh Dickins
2011-01-29  2:59                           ` Mario Kleiner
2011-01-30  0:28                             ` Hugh Dickins
2011-01-30  4:13                               ` Mario Kleiner
2011-01-30  9:55                                 ` Chris Wilson
2011-01-31 10:57                                   ` [PATCH] drm/i915: Suppress spurious vblank interrupts Chris Wilson
2011-02-01 17:34                                     ` Hugh Dickins
2011-02-01 17:46                                       ` Chris Wilson
2011-02-01 17:46                                       ` Jesse Barnes
2011-02-01 18:08                                         ` Jesse Barnes
2011-02-01 18:46                                           ` Hugh Dickins [this message]
2011-02-01 19:32                                             ` Jesse Barnes
2011-02-02  3:37                                               ` Hugh Dickins
2011-02-02 17:18                                                 ` Jesse Barnes
2011-02-08 19:52                                                   ` Hugh Dickins
2011-02-10 10:16                                                     ` [PATCH] drm/i915/tv: Use polling rather than interrupt-based hotplug Chris Wilson
2011-02-11  6:34                                                       ` Hugh Dickins
2011-02-11 18:21                                                     ` [PATCH] drm/i915: Suppress spurious vblank interrupts Mario Kleiner
2011-02-14 17:41                                                       ` Hugh Dickins
2011-06-18  4:40                                                         ` Hugh Dickins
2011-01-30  8:52                               ` [PATCH] drm/i915,agp/intel: Do not clear stolen entries Chris Clayton
2011-01-21 16:05             ` [BISECTED] agp/intel: revert "Remove confusion of stolen entries not stolen memory" Jiri Olsa

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