From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937878AbcKNCfP (ORCPT ); Sun, 13 Nov 2016 21:35:15 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:47402 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964984AbcKNCfK (ORCPT ); Sun, 13 Nov 2016 21:35:10 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Jani Nikula" , "Daniel Vetter" , "Mario Kleiner" , "Dave Airlie" , "Ville =?UTF-8?Q?Syrj=C3=A4l=C3=A4?=" Date: Mon, 14 Nov 2016 00:14:20 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 158/346] drm/i915/dp: Revert "drm/i915/dp: fall back to 18 bpp when sink capability is unknown" In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.39-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Mario Kleiner commit 196f954e250943df414efd3d632254c29be38e59 upstream. This reverts commit 013dd9e03872 ("drm/i915/dp: fall back to 18 bpp when sink capability is unknown") This commit introduced a regression into stable kernels, as it reduces output color depth to 6 bpc for any video sink connected to a Displayport connector if that sink doesn't report a specific color depth via EDID, or if our EDID parser doesn't actually recognize the proper bpc from EDID. Affected are active DisplayPort->VGA converters and active DisplayPort->DVI converters. Both should be able to handle 8 bpc, but are degraded to 6 bpc with this patch. The reverted commit was meant to fix Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=105331 A followup patch implements a fix for that specific bug, which is caused by a faulty EDID of the affected DP panel by adding a new EDID quirk for that panel. DP 18 bpp fallback handling and other improvements to DP sink bpc detection will be handled for future kernels in a separate series of patches. Please backport to stable. Signed-off-by: Mario Kleiner Acked-by: Jani Nikula Cc: Ville Syrjälä Cc: Daniel Vetter Signed-off-by: Dave Airlie Signed-off-by: Ben Hutchings --- drivers/gpu/drm/i915/intel_display.c | 20 +++++--------------- 1 file changed, 5 insertions(+), 15 deletions(-) --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -9475,21 +9475,11 @@ connected_sink_compute_bpp(struct intel_ pipe_config->pipe_bpp = connector->base.display_info.bpc*3; } - /* Clamp bpp to default limit on screens without EDID 1.4 */ - if (connector->base.display_info.bpc == 0) { - int type = connector->base.connector_type; - int clamp_bpp = 24; - - /* Fall back to 18 bpp when DP sink capability is unknown. */ - if (type == DRM_MODE_CONNECTOR_DisplayPort || - type == DRM_MODE_CONNECTOR_eDP) - clamp_bpp = 18; - - if (bpp > clamp_bpp) { - DRM_DEBUG_KMS("clamping display bpp (was %d) to default limit of %d\n", - bpp, clamp_bpp); - pipe_config->pipe_bpp = clamp_bpp; - } + /* Clamp bpp to 8 on screens without EDID 1.4 */ + if (connector->base.display_info.bpc == 0 && bpp > 24) { + DRM_DEBUG_KMS("clamping display bpp (was %d) to default limit of 24\n", + bpp); + pipe_config->pipe_bpp = 24; } }