From: Daniel Vetter <daniel@ffwll.ch>
To: Zdenek Kabelac <zdenek.kabelac@gmail.com>,
Sean Paul <seanpaul@chromium.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
intel-gfx@lists.freedesktop.org, jbarnes@virtuousgeek.org
Subject: Re: Regression on GMA965 - display seems to have slow jump changes in brightness
Date: Wed, 23 May 2012 11:11:09 +0200 [thread overview]
Message-ID: <20120523091109.GI5062@phenom.ffwll.local> (raw)
In-Reply-To: <20120523070728.GC5062@phenom.ffwll.local>
On Wed, May 23, 2012 at 09:07:28AM +0200, Daniel Vetter wrote:
> On Wed, May 23, 2012 at 08:59:07AM +0200, Zdenek Kabelac wrote:
> > Hmm I've been using i915.lvds_downclock=1 on grub command line, and
> > haven't noticed any visible problems with 3.3 kernel. So I'd rather
> > ask if the problematic patch isn't doing downclocking in a wrong way?
> > Or maybe detection that downclocking is not supported properly is not
> > correct now ?
>
> Nope, Sean's analysis is pretty much correct, that patch only makes
> downclocking possible in more circumstances. And downclocking can
> certainly explain what you're seeing, the backlight pwm signal is driven
> off the panel dotclock, so if we change that we can very likely cause some
> funny interference. I guess we could frob the backligth control settings
> and adjust them for the change in clockspeed, but the current backlight
> code is a bit a mess. So right now I suggest you just drop that option -
> there are reasons it's not the default ;-)
Quick question: What's the frequency of the brightness change? And how
regular are the changes?
-Daniel
--
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48
next prev parent reply other threads:[~2012-05-23 9:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-22 12:08 Zdenek Kabelac
2012-05-22 12:30 ` Daniel Vetter
2012-05-22 14:36 ` Zdenek Kabelac
2012-05-22 14:44 ` Daniel Vetter
2012-05-22 14:55 ` Zdenek Kabelac
2012-05-22 22:15 ` Zdenek Kabelac
2012-05-22 22:21 ` Sean Paul
2012-05-23 6:49 ` Daniel Vetter
2012-05-23 6:59 ` Zdenek Kabelac
2012-05-23 7:07 ` Daniel Vetter
2012-05-23 9:11 ` Daniel Vetter [this message]
2012-05-23 11:48 ` Zdenek Kabelac
2012-05-23 12:03 ` [Intel-gfx] " Daniel Vetter
2012-05-24 14:21 ` Zdenek Kabelac
2012-05-24 14:41 ` Daniel Vetter
2012-05-23 8:59 ` Chris Wilson
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