[Dell Latitude E6440] [Firmware Bug]: ACPI(PEGP) defines _DOD but not _DOS

[Po-Hsu Lin]

CID: 201306-13688 Dell Latitude E6440

The following HIGH failure could be found in Kernel message:
[ 10.936059] [Firmware Bug]: ACPI(PEGP) defines _DOD but not _DOS

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.8.0-33-generic 3.8.0-33.48~precise1
ProcVersionSignature: Ubuntu 3.8.0-33.48~precise1-generic 3.8.13.11
Uname: Linux 3.8.0-33-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version k3.8.0-33-generic.
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 1: PCH [HDA Intel PCH], device 0: ALC292 Analog [ALC292 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: ubuntu 1840 F.... pulseaudio
 /dev/snd/controlC0: ubuntu 1840 F.... pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'MID'/'HDA Intel MID at 0xf7d34000 irq 46'
   Mixer name : 'Intel Haswell HDMI'
   Components : 'HDA:80862807,80860101,00100000'
   Controls : 21
   Simple ctrls : 3
Card1.Amixer.info:
 Card hw:1 'PCH'/'HDA Intel PCH at 0xf7d30000 irq 47'
   Mixer name : 'Realtek ALC292'
   Components : 'HDA:10ec0292,102805bd,00100001'
   Controls : 23
   Simple ctrls : 10
Date: Mon Nov 11 16:17:18 2013
HibernationDevice: RESUME=UUID=aeb30de4-c85d-4d93-874d-8f06ce1303b2
InstallationMedia: Ubuntu 12.04.3 LTS "Precise Pangolin" - Release amd64 (20130820.1)
MachineType: Dell Inc. Latitude E6440
MarkForUpload: True
ProcEnviron:
 LANGUAGE=zh_TW:
 TERM=xterm
 PATH=(custom, no user)
 LANG=zh_TW.UTF-8
 SHELL=/bin/bash
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-33-generic root=UUID=f1222250-3d7e-4a89-b724-e360c15513ec ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.8.0-33-generic N/A
 linux-backports-modules-3.8.0-33-generic N/A
 linux-firmware 1.79.7
SourcePackage: linux-lts-raring
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 07/03/2013
dmi.bios.vendor: Dell Inc.
dmi.bios.version: X23
dmi.board.name: 02P3T1
dmi.board.vendor: Dell Inc.
dmi.board.version: X03
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrX23:bd07/03/2013:svnDellInc.:pnLatitudeE6440:pvr01:rvnDellInc.:rn02P3T1:rvrX03:cvnDellInc.:ct9:cvr:
dmi.product.name: Latitude E6440
dmi.product.version: 01
dmi.sys.vendor: Dell Inc.

[Alex Hung (alexhung)]

According to ACPI spec, _DOS "indicates that the system BIOS is capable of automatically switching the active display output or controlling the brightness of the LCD."

However, kernel commit b03738430c7537d5f87948e0b35d8aaf2688c6b4 works around it a while ago:
commit b03738430c7537d5f87948e0b35d8aaf2688c6b4
Author: Zhang Rui <email address hidden>
Date: Wed Jun 20 09:48:43 2012 +0800

    ACPI video: Still use ACPI backlight control if _DOS doesn't exist

    This fixes a regression in 3.4-rc1 caused by commit
    ea9f8856bd6d4ed45885b06a338f7362cd6c60e5
    (ACPI video: Harden video bus adding.)

    Some platforms don't have _DOS control method, but the ACPI
    backlight still works.
    We should not invoke _DOS for these platforms.

    https://bugzilla.kernel.org/show_bug.cgi?id=43168

    Cc: Igor Murzov <email address hidden>
    Cc: <email address hidden>
    Signed-off-by: Zhang Rui <email address hidden>
    Signed-off-by: Len Brown <email address hidden>

I also confirmed brightness controls (hotkey) work as expected in 12.04.03

[Alex Hung (alexhung)]

I also verified the display switch with d-sub interface, and display switch works automatically when d-sub monitor is attached.

[Alex Hung (alexhung)]

While it is certainly a firmware bug indeed as BIOS's DSDT violate acpi spec, it seems no function is lost as kernel workaround it.

[Alex Hung (alexhung)]

Checking drivers/acpi/video.c also found it outputs a warning message but with no control flow changes as below:

static int acpi_video_bus_check(struct acpi_video_bus *video)
{
        ...
        /* Does this device support video switching? */
        if (video->cap._DOS || video->cap._DOD) {
                if (!video->cap._DOS) {
                        printk(KERN_WARNING FW_BUG
                                "ACPI(%s) defines _DOD but not _DOS\n",
                                acpi_device_bid(video->device));
                }
                video->flags.multihead = 1;
                status = 0;
        }
}

Therefore it is safe to ignore it. We will also investigate whether it is appropriate to lower the severity in fwts.

        ...

[Colin Ian King (colin-king)]

I'm happy for this to be dropped to a LOW priority issue.

[Alex Hung (alexhung)]

@colin,

Thanks, I will develop a patch for it.

[Alex Hung (alexhung)]

fwts patch is sent for review @ https://lists.ubuntu.com/archives/fwts-devel/2013-November/004027.html

[Taihsiang Ho (tai271828)]

tested 201306-13688 on 12.04.4 and the statement does be move to LOW priority in fwts testing.
Remove useless tags.
(I think tag 201306-16388 is a typo)