From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752773Ab2AYVwr (ORCPT ); Wed, 25 Jan 2012 16:52:47 -0500 Received: from mail-wi0-f174.google.com ([209.85.212.174]:59650 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752392Ab2AYVwq (ORCPT ); Wed, 25 Jan 2012 16:52:46 -0500 Date: Wed, 25 Jan 2012 22:52:45 +0100 From: Daniel Vetter To: Keith Packard Cc: intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Lubos Kolouch Subject: Re: [Intel-gfx] [PATCH 1/2] drm/i915: Force explicit bpp selection for intel_dp_link_required Message-ID: <20120125215245.GJ3896@phenom.ffwll.local> Mail-Followup-To: Keith Packard , intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Lubos Kolouch References: <1327508186-26704-1-git-send-email-keithp@keithp.com> <1327508186-26704-2-git-send-email-keithp@keithp.com> MIME-Version: 1.0 In-Reply-To: <1327508186-26704-2-git-send-email-keithp@keithp.com> X-Operating-System: Linux phenom 3.2.0-1-amd64 User-Agent: Mutt/1.5.21 (2010-09-15) Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 25, 2012 at 08:16:25AM -0800, Keith Packard wrote: > It is never correct to use intel_crtc->bpp in intel_dp_link_required, > so instead pass an explicit bpp in to this function. This patch > only supports 18bpp and 24bpp modes, which means that 10bpc modes will > be computed incorrectly. Fixing that will require more extensive > changes, and so must be addressed separately from this bugfix. > > intel_dp_link_required is called from intel_dp_mode_valid and > intel_dp_mode_fixup. > > * intel_dp_mode_valid is called to list supported modes; in this case, > the current crtc values cannot be relevant as the modes in question > may never be selected. Thus, using intel_crtc->bpp is never right. > > * intel_dp_mode_fixup is called during mode setting, but it is run > well before ironlake_crtc_mode_set is called to set intel_crtc->bpp, > so using intel_crtc-bpp in this path can only ever get a stale > value. > > Cc: Lubos Kolouch > Cc: Adam Jackson > Signed-off-by: Keith Packard Afaics this is correct and should fix quite a few "dp doesn't light up issue" (in combination with 6bpc auto-dither code that's already there). I think all the open issues are only about how to make this less pessimistic and more generic, i.e. patch 2. Reviewed-by: Daniel Vetter -- Daniel Vetter Mail: daniel@ffwll.ch Mobile: +41 (0)79 365 57 48