From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D2717C54E58 for ; Fri, 15 Mar 2024 11:02:37 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3C294112161; Fri, 15 Mar 2024 11:02:37 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="C+zrW4Lf"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.20]) by gabe.freedesktop.org (Postfix) with ESMTPS id 05A56112161 for ; Fri, 15 Mar 2024 11:02:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1710500556; x=1742036556; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=PhSY4PLYn9ZN19nZklsdPSRtshBOld/M1zr7xnXGST4=; b=C+zrW4LfzIhIumruKBMASArM7SNX/Ogr9cg/HzBnTDz4prPppdFAb1Gr O9+gcc+Cv2iKkRbHIRn43beUTJQNPvSjN+i3LFyyflwRAECRKMEPhiRW5 joHbG6NRnT/S31bVUX2s6svo0nGSPDMmiMZzJMiMJt27SzbUGmeXm9emv Yvi7HbfgtS+qVeGEcTIjYFPFv0BwXmqrgkpnRYpp60J2XRA6K9wTPS/Io vgl/RG+a21XZ+Y7V3BLQF+9ww7I9SKwn+cVihzei9Cl8g+BZe3BFmyDPy qpsyx8IB9eI52TPDjUplpHJQ6EBXFSO2IrcUstyIhxLg39OPMWfjCLD5b A==; X-IronPort-AV: E=McAfee;i="6600,9927,11013"; a="5229063" X-IronPort-AV: E=Sophos;i="6.07,128,1708416000"; d="scan'208";a="5229063" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orvoesa112.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Mar 2024 04:02:35 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,11013"; a="827780566" X-IronPort-AV: E=Sophos;i="6.07,128,1708416000"; d="scan'208";a="827780566" Received: from stinkpipe.fi.intel.com (HELO stinkbox) ([10.237.72.74]) by orsmga001.jf.intel.com with SMTP; 15 Mar 2024 04:02:32 -0700 Received: by stinkbox (sSMTP sendmail emulation); Fri, 15 Mar 2024 13:02:32 +0200 Date: Fri, 15 Mar 2024 13:02:32 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Jani Nikula Cc: gareth.yu@intel.com, intel-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/i915/display: Fixed a screen flickering when turning on display from off Message-ID: References: <20240306031348.1344034-1-gareth.yu@intel.com> <87il1zzmpt.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87il1zzmpt.fsf@intel.com> X-Patchwork-Hint: comment X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Wed, Mar 06, 2024 at 12:19:42PM +0200, Jani Nikula wrote: > On Wed, 06 Mar 2024, gareth.yu@intel.com wrote: > > From: Gareth Yu > > > > Turn on the panel from zero brightness of the last state, the panel was set > > a maximum PWM in the flow. Once the panel initialization is completed, the > > backlight is restored to zero brightness. There is a flckering generated. > > Please be more precise in describing what exactly happens and > when. Driver probe? Modeset? What restores backlight to zero brightness? > > Better yet, please file a bug at fdo gitlab, attach full dmesg with > debugs, etc. > > Before we had the concept of minimum brightness, the minimum was always > 0. And the check was: > > if (level == 0) > level = max; > > Historically, the point was, if you're enabling the display and > backlight, you don't want it to be at 0 brightness, because for most > displays that means a black screen. I think that hack was originally added becaue some silly userspace thingy was setting the backlight level to 0 on suspend/etc. and then forgetting to restore it back to a sane value afterwards. Dunno if that nonsense behaviour still persists to this day. -- Ville Syrjälä Intel