Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964816Ab2EWLso (ORCPT ); Wed, 23 May 2012 07:48:44 -0400 Received: from mail-ob0-f174.google.com ([209.85.214.174]:42702 "EHLO mail-ob0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932305Ab2EWLsm (ORCPT ); Wed, 23 May 2012 07:48:42 -0400 MIME-Version: 1.0 In-Reply-To: <20120523091109.GI5062@phenom.ffwll.local> References: <20120522123058.GB4629@phenom.ffwll.local> <20120522144443.GD4629@phenom.ffwll.local> <20120523070728.GC5062@phenom.ffwll.local> <20120523091109.GI5062@phenom.ffwll.local> Date: Wed, 23 May 2012 13:48:41 +0200 Message-ID: Subject: Re: Regression on GMA965 - display seems to have slow jump changes in brightness From: Zdenek Kabelac To: Zdenek Kabelac , Sean Paul , Linux Kernel Mailing List , intel-gfx@lists.freedesktop.org, jbarnes@virtuousgeek.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1881 Lines: 40 2012/5/23 Daniel Vetter : > 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 Now when it's obvious it's related to powersaving - it's probably much easier to explain, that I've been observing those changes when some activity was happing - i.e. opening picture - and after like 1 second image has flashed, - then I've moved the mouse stopped - and again image has flashed with brightness a bit. The issue would be probably far less noticeable if the period of time of idle GPU would have to be much longer (i.e. in minute range) Zdenek -- 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/