From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jonathan Nieder Subject: [3.2.y, 3.4.y, 3.5.y] Re: [PATCH] drm/i915: prefer wide & slow to fast & narrow in DP configs Date: Sun, 5 Aug 2012 17:12:06 -0700 Message-ID: <20120806001206.GA1376@Jonathans-MacBook-Air.local> References: <1340316830-15601-1-git-send-email-jbarnes@virtuousgeek.org> <86pq8sqhcg.fsf@sumi.keithp.com> <1340355948_38587@CP5-2952> <86a9zvqm7t.fsf@sumi.keithp.com> <1340387615_42474@CP5-2952> <20120704074209.GD5375@phenom.ffwll.local> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pb0-f49.google.com (mail-pb0-f49.google.com [209.85.160.49]) by gabe.freedesktop.org (Postfix) with ESMTP id BBFBF9E737 for ; Sun, 5 Aug 2012 17:12:08 -0700 (PDT) Received: by pbbrq13 with SMTP id rq13so4955061pbb.36 for ; Sun, 05 Aug 2012 17:12:08 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20120704074209.GD5375@phenom.ffwll.local> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Daniel Vetter Cc: intel-gfx@lists.freedesktop.org, stable@vger.kernel.org List-Id: intel-gfx@lists.freedesktop.org Hi Ben, Greg, et al, Please consider 2514bc510d0c drm/i915: prefer wide & slow to fast & narrow in DP configs, 2012-06-21 for application to the 3.2.y, 3.4.y, and 3.5.y trees. It addresses a regression which bisects to v3.2-rc1~135^2~2^2~7 (drm/i915/dp: Fix the math in intel_dp_link_required, 2011-10-14). An external display connected through DisplayPort would give "DP no signal" unless the resolution was overridden to be artificially low. In discussion of the patch, two worries came up: - In older kernels, some machines lied about the maximum number of DP lanes. Luckily v3.2-rc3~8^2~5^2~2 (drm/i915: Use DPCD value for max DP lanes, 2011-11-02) solved that, so the patch should be safe. - Using the minimum lane count is the right thing to do to minimize power consumption. But a working display is more important. Peter who discovered the bug tested the patch in June and found it to work. He tried it against a 3.2.y tree in July and it still worked. The patch has been in mainline for about a week and a half and in Debian's 3.2.y-based kernel since around the same time. No complaints yet. Thoughts of all kinds welcome, as usual. Hope that helps, Jonathan