Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933139AbaDCDNM (ORCPT ); Wed, 2 Apr 2014 23:13:12 -0400 Received: from mail-wi0-f179.google.com ([209.85.212.179]:48957 "EHLO mail-wi0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932843AbaDCDNK (ORCPT ); Wed, 2 Apr 2014 23:13:10 -0400 From: James Hogan To: Jani Nikula , Imre Deak , Kamal Mostafa , Daniel Vetter , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: drm/i915: XPS13 backlight regression in v3.14 Date: Thu, 03 Apr 2014 04:12:58 +0100 Message-ID: <2613018.1cXJgVWlHm@radagast> User-Agent: KMail/4.11.5 (Linux/3.14.0+; KDE/4.11.5; x86_64; ; ) MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1540737.b7YM2oHPVp"; micalg="pgp-sha1"; protocol="application/pgp-signature" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --nextPart1540737.b7YM2oHPVp Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" 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? Thanks James --nextPart1540737.b7YM2oHPVp Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part. Content-Transfer-Encoding: 7Bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAABAgAGBQJTPNHCAAoJEGwLaZPeOHZ66tMP+gOV3J4/bQWI+6TBHVAX9Z5N +HA8/zijmRo0X8Jkaeg2f9MRMdWY4GycmSEcS2dvrOLLd+Tgfj1k7rK9zdNQiGq4 b3ufjEnSZU59Ysm7q0I0YfZaRDxUZkZ5gRse4P1Z9htY8/Ip75caTC66LSnU7T80 yFZTQJfuAHJ7TjPHzo84my7cP5NPwfzj+9FrYB8bmejSDvPd8rXcMckF30LsFYYf TgMJ6MrDdyEeQY3aWw2gp2I3KgKpP3rQF8vXs4Q9Fqbx2jPpKqoseXraTzD90RXu 2F4kTbqKXXApHPfAq446ZemB/PXMxxxHoysfeByJSt+JeloxvhUuUPmVp4MrMbpR nolCv+gtv36rVQh37+V+KKJS94Zo8TUC6Q+Z1tpqZ3RQjnlIGoniq5BsDDx6Q5xg 2H5FNJbP5KfKH2LLX3E0xWO0u24uPiEuVmthzSit2YnzqxajfcZiszXRxRME5Cfi S+9VCv53hTpF7IiSRLb/9L4EPFu9oj95HN8iAhPYm5yhieWtuoKd0I8fWpqnl+My EVDTfyAsKXMzzGyoY2KcrgB2QXfTS0toQnRrcoTjLxnAhD1HsLmnw0ZsiVYSULbt 4c5d+9grYSCu+dqZ6vAy4TdNsY+762N0oCTL6qqUjnTqEfuQGdUg2k0YE5CGtG0e 6MevAiqSgtfPbAE4nnzy =8Mlo -----END PGP SIGNATURE----- --nextPart1540737.b7YM2oHPVp-- -- 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/