From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesse Barnes Subject: Re: [PATCH] drm/i915: prefer wide & slow to fast & narrow in DP configs Date: Fri, 22 Jun 2012 09:29:18 -0700 Message-ID: <20120622092918.29c345d6@jbarnes-desktop> References: <1340316830-15601-1-git-send-email-jbarnes@virtuousgeek.org> <86pq8sqhcg.fsf@sumi.keithp.com> <1340355948_38587@CP5-2952> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from oproxy8-pub.bluehost.com (oproxy8-pub.bluehost.com [69.89.22.20]) by gabe.freedesktop.org (Postfix) with SMTP id 53047A0FE7 for ; Fri, 22 Jun 2012 09:29:19 -0700 (PDT) In-Reply-To: <1340355948_38587@CP5-2952> 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: Chris Wilson Cc: intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org On Fri, 22 Jun 2012 10:05:19 +0100 Chris Wilson wrote: > On Thu, 21 Jun 2012 18:13:19 -0700, Keith Packard wrote: > > Jesse Barnes writes: > > > > > High frequency link configurations have the potential to cause trouble > > > with long and/or cheap cables, so prefer slow and wide configurations > > > instead. This patch has the potential to cause trouble for eDP > > > configurations that lie about available lanes, so if we run into that we > > > can make it conditional on eDP. > > > > I *have* run into this on eDP machines already, which is why the code > > loops this way today... > > It was structured to minimise lane count because certain chipsets did > not wire up all the lanes, right? Is that still relevant as we are using > the advertised max_lane_count from the DPCD now? In embedded applications, some of the lanes may not exist, but the DPCD should indicate that (though as Keith says, some lie about it). But if we set aside eDP it may be safe... -- Jesse Barnes, Intel Open Source Technology Center