Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162430AbaDCHF3 (ORCPT ); Thu, 3 Apr 2014 03:05:29 -0400 Received: from mga09.intel.com ([134.134.136.24]:33924 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1162382AbaDCHFW (ORCPT ); Thu, 3 Apr 2014 03:05:22 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,784,1389772800"; d="scan'208";a="513904184" From: Jani Nikula To: James Hogan , Imre Deak , Kamal Mostafa , Daniel Vetter , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: drm/i915: XPS13 backlight regression in v3.14 In-Reply-To: <2613018.1cXJgVWlHm@radagast> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <2613018.1cXJgVWlHm@radagast> User-Agent: Notmuch/0.17+162~g34940eaa1d37 (http://notmuchmail.org) Emacs/24.3.1 (x86_64-pc-linux-gnu) Date: Thu, 03 Apr 2014 10:02:58 +0300 Message-ID: <87zjk2lwt9.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 03 Apr 2014, James Hogan wrote: > Hi, > > I've noticed that v3.14 breaks the backlight on Dell XPS13. Reverting the > following commit fixes the issue for me (i.e. the GUI brightness controls work > again): > > bc0bb9fd1c78 drm/i915: remove QUIRK_NO_PCH_PWM_ENABLE > > It appears that in v3.14 (with the above patch): > * intel_backlight/brightness=4882 (max & default) causes > acpi_video0/brightness to have no effect. > * intel_backlight/brightness=0 causes acpi_video0/brightness to behave > corrrectly (the firmware (I assume) fades the brightness gradually when > acpi_video0/brightness is set) > * intel_backlight/brightness=something else in between often causes > acpi_video0 and intel_backlight to apparently "fight" over the backlight, > resulting in brightness flickering up and down every second or so. > > Reverting the above patch on v3.14: > * intel_backlight/brightness has no effect > * acpi_video0/brightness works normally > > It doesn't seem quite as simple as them trying to use the same hardware since > when intel_backlight/brightness=4882, acpi_video0/brightness has no effect at > all, so I don't really get what's going on. > > Can anybody shed some light or suggest a proper fix for this recurring issue? Tracked at https://bugs.freedesktop.org/show_bug.cgi?id=76276 BR, Jani. > > Thanks > James -- Jani Nikula, Intel Open Source Technology Center -- 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/