Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755947Ab2EWJJw (ORCPT ); Wed, 23 May 2012 05:09:52 -0400 Received: from mail-we0-f174.google.com ([74.125.82.174]:60510 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754970Ab2EWJJu (ORCPT ); Wed, 23 May 2012 05:09:50 -0400 Date: Wed, 23 May 2012 11:11:09 +0200 From: Daniel Vetter To: Zdenek Kabelac , Sean Paul , Linux Kernel Mailing List , intel-gfx@lists.freedesktop.org, jbarnes@virtuousgeek.org Subject: Re: Regression on GMA965 - display seems to have slow jump changes in brightness Message-ID: <20120523091109.GI5062@phenom.ffwll.local> Mail-Followup-To: Zdenek Kabelac , Sean Paul , Linux Kernel Mailing List , intel-gfx@lists.freedesktop.org, jbarnes@virtuousgeek.org References: <20120522123058.GB4629@phenom.ffwll.local> <20120522144443.GD4629@phenom.ffwll.local> <20120523070728.GC5062@phenom.ffwll.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120523070728.GC5062@phenom.ffwll.local> X-Operating-System: Linux phenom 3.4.0-rc6+ User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1419 Lines: 29 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/