From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754167Ab1KMQYV (ORCPT ); Sun, 13 Nov 2011 11:24:21 -0500 Received: from mail-bw0-f46.google.com ([209.85.214.46]:56066 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752834Ab1KMQYU (ORCPT ); Sun, 13 Nov 2011 11:24:20 -0500 Message-ID: <4EBFEF29.9050005@gmail.com> Date: Sun, 13 Nov 2011 17:24:09 +0100 From: Daniel Mack User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20110930 Thunderbird/7.0.1 MIME-Version: 1.0 To: Takashi Iwai CC: dri-devel@lists.freedesktop.org, jbarnes@virtuousgeek.org, harald@redhat.com, Keith Packard , linux-kernel@vger.kernel.org Subject: Re: Strange effect with i915 backlight controller References: <4EB3F860.6010408@gmail.com> <4EB87E6A.3060403@gmail.com> <4EBBE9A1.8020501@gmail.com> In-Reply-To: X-Enigmail-Version: 1.3.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Takashi, On 11/10/2011 04:39 PM, Takashi Iwai wrote: > At Thu, 10 Nov 2011 16:11:29 +0100, > Daniel Mack wrote: >> >> On 11/08/2011 01:57 AM, Daniel Mack wrote: >>> Didn't get any response yet, hence copying LKML for a broader audience. >> >> Nobody, really? >> >> This is a rather annoying regression, as touching the brightness keys >> appearantly switches off the whole machine. I'm sure this is trivial to >> fix, I just don't have the insight of this driver and the chipset. > > I vaguely remember that the bit 0 is invalid on some old chips. > Maybe 915GM is one of them, as it's gen3? If so, the patch like below > may work. Thank you for looking into this. > --- > diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c > index 499d4c0..be952d1 100644 > --- a/drivers/gpu/drm/i915/intel_panel.c > +++ b/drivers/gpu/drm/i915/intel_panel.c > @@ -249,8 +249,11 @@ static void intel_panel_actually_set_backlight(struct drm_device *dev, u32 level > if (IS_PINEVIEW(dev)) { > tmp &= ~(BACKLIGHT_DUTY_CYCLE_MASK - 1); > level <<= 1; > - } else > + } else { > tmp &= ~BACKLIGHT_DUTY_CYCLE_MASK; > + if (INTEL_INFO(dev)->gen < 4) > + tmp &= ~1; > + } > I915_WRITE(BLC_PWM_CTL, tmp | level); > } > This seems to be the right intention, but the value you want to modify under this condition is 'level', not 'tmp'. With this amendment of your patch, things work perfectly fine here. You can add my Reported-and-tested-by: Daniel Mack and please Cc: stable so we get this to the users asap. Thanks! Daniel