From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jani Nikula Subject: Re: [PATCH] drm/i915/opregion: work around buggy firmware that provides 8+ output devices Date: Wed, 12 Feb 2014 12:52:13 +0200 Message-ID: <87vbwky55u.fsf@intel.com> References: <52FAE504.8020001@intel.com> <20140212103156.GC5298@nuc-i3427.alporthouse.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by gabe.freedesktop.org (Postfix) with ESMTP id E05F9FADE3 for ; Wed, 12 Feb 2014 02:48:26 -0800 (PST) In-Reply-To: <20140212103156.GC5298@nuc-i3427.alporthouse.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org To: Chris Wilson , Aaron Lu Cc: Matthew Garrett , Daniel Vetter , "intel-gfx@lists.freedesktop.org" , "Rafael J. Wysocki" , "linux-kernel@vger.kernel.org" , Oleksij Rempel , ACPI Devel Mailing List List-Id: intel-gfx@lists.freedesktop.org On Wed, 12 Feb 2014, Chris Wilson wrote: > On Wed, Feb 12, 2014 at 11:05:40AM +0800, Aaron Lu wrote: >> The ACPI table on ASUS UX302LA has more than 8 output devices under the >> graphics controller device node. The problem is, the real active output >> device, the LCD panel, is listed the last. The result is, the LCD's >> device id doesn't get recorded in the active device list CADL array and >> when the _DCS control method for the LCD device is executed, it returns >> 0x1d, meaning it is not active. This affects the hotkey delivery ASL >> code that will not deliver a notification if the output device is not >> active on backlight hotkey press. >> >> I don't see a clean way to solve this problem since the operation region >> spec doesn't allow more than 8 output devices so we have no way of >> storing all these output devices. The fact that output devices that have >> _BCM control method usually means they have a higher possibility of being >> used than those who don't made me choose a simple way to work around >> the buggy firmware by replacing the last entry in CADL array with the one >> that has _BCM control method. There is no specific reason why the last >> entry is picked instead of others. > > Another possibility is that the connector list is in rough priority > order so might be useful for sorting the CADL array. > > Since the CADL should only be a list of currently active devices, we > could just bite the bullet and repopulate it correctly after every > setcrtc. Agreed. Per spec, DIDL: Writes - Graphics driver writes to this field once during its initialization after determining platform supported connectors. CPDL: Writes - Graphics driver writes to this field on every monitor detection process. CADL: Writes - Graphics driver writes to this field on every mode set process and during boot. And for all of the above: Writes - System BIOS POST or ASL code should not write to these fields. BR, Jani. -- Jani Nikula, Intel Open Source Technology Center