From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jani Nikula Subject: Re: Regression: Backlight not coming on after resume. Date: Fri, 01 Mar 2013 16:47:33 +0200 Message-ID: <87ip5bw516.fsf@intel.com> References: <87lia8mp0b.fsf@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mga03.intel.com (mga03.intel.com [143.182.124.21]) by gabe.freedesktop.org (Postfix) with ESMTP id 77C57E6830 for ; Fri, 1 Mar 2013 06:47:10 -0800 (PST) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: James Courtier-Dutton , Takashi Iwai Cc: Intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org Hi James - On Fri, 01 Mar 2013, James Courtier-Dutton wrote: >> James, try to revert that commit. Does it fix? >> >> If so, you should check the output of intel_reg_dumper at broken and >> working states. >> > Can someone point me to a datasheet that relates to this bit of code, so i > can understand what all the registers do. > I would like to understand the code in order to suggest a better fix. https://01.org/linuxgraphics/documentation/driver-documentation-prms Vol 3 is the relevant volume in each generation. I don't think any of the docs back up the comments in the bad commit saying "BLC_PWM_CPU_CTL is cleared to zero automatically when BLC_PWM_CPU_CTL2 and BLC_PWM_PCH_CTL1 are written" though. I guess it could be some bad ACPI/BIOS interaction too. I'd still urge you to file the bug, and attach the dmesgs and register dumps first. And let us know if the revert fixes it. BR, Jani.