[Bug 49789] New: External monitor flickers on xrandr or cat /sys/class/drm/card0-VGA-1/status

[Bug 49789] New: External monitor flickers on xrandr or cat /sys/class/drm/card0-VGA-1/status

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=49789

             Bug #: 49789
           Summary: External monitor flickers on xrandr or cat
                    /sys/class/drm/card0-VGA-1/status
    Classification: Unclassified
           Product: DRI
           Version: XOrg CVS
          Platform: x86-64 (AMD64)
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Radeon
        AssignedTo: dri-devel@lists.freedesktop.org
        ReportedBy: h.judt@gmx.at


Created attachment 61441
  --> https://bugs.freedesktop.org/attachment.cgi?id=61441
Xorg.log

This issue is not reproducible with every external monitor, as far as I could
determine only projectors are concerned:

When I connect a monitor/projector to the VGA port of the Lenovo T400 and
perform "xrandr" or "cat /sys/class/drm/card0-VGA-1/status", the external
monitor flickers (parts of the screen black out horizontally). Since I use a
script which performs these commands periodically to detect whether the monitor
is still connected, this is obviously very annoying.

Changing the power profile doesn't have any effect.

lspci:
01:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI RV620
[Mobility Radeon HD 3400 Series] (prog-if 00 [VGA controller])
        Subsystem: Lenovo Device 210e
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B- DisINTx+
        Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort-
<MAbort- >SERR- <PERR- INTx-
        Latency: 0, Cache Line Size: 64 bytes
        Interrupt: pin A routed to IRQ 45
        Region 0: Memory at d0000000 (32-bit, prefetchable) [size=256M]
        Region 1: I/O ports at 2000 [size=256]
        Region 2: Memory at cfff0000 (32-bit, non-prefetchable) [size=64K]
        [virtual] Expansion ROM at cff00000 [disabled] [size=128K]
        Capabilities: [50] Power Management version 3
                Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA
PME(D0-,D1-,D2-,D3hot-,D3cold-)
                Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
        Capabilities: [58] Express (v2) Legacy Endpoint, MSI 00
                DevCap: MaxPayload 128 bytes, PhantFunc 0, Latency L0s <4us, L1
unlimited
                        ExtTag+ AttnBtn- AttnInd- PwrInd- RBE+ FLReset-
                DevCtl: Report errors: Correctable- Non-Fatal- Fatal-
Unsupported-
                        RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+
                        MaxPayload 128 bytes, MaxReadReq 128 bytes
                DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr-
TransPend-
                LnkCap: Port #0, Speed 2.5GT/s, Width x16, ASPM L0s L1, Latency
L0 <64ns, L1 <1us
                        ClockPM- Surprise- LLActRep- BwNot-
                LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- Retrain- CommClk+
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
                LnkSta: Speed 2.5GT/s, Width x16, TrErr- Train- SlotClk+
DLActive- BWMgmt- ABWMgmt-
                DevCap2: Completion Timeout: Not Supported, TimeoutDis-
                DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-
                LnkCtl2: Target Link Speed: 2.5GT/s, EnterCompliance-
SpeedDis-, Selectable De-emphasis: -6dB
                         Transmit Margin: Normal Operating Range,
EnterModifiedCompliance- ComplianceSOS-
                         Compliance De-emphasis: -6dB
                LnkSta2: Current De-emphasis Level: -3.5dB,
EqualizationComplete-, EqualizationPhase1-
                         EqualizationPhase2-, EqualizationPhase3-,
LinkEqualizationRequest-
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
                Address: 00000000fee0100c  Data: 41a1
        Capabilities: [100 v1] Vendor Specific Information: ID=0001 Rev=1
Len=010 <?>
        Kernel driver in use: radeon

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[Bug 49789] External monitor flickers on xrandr or cat /sys/class/drm/card0-VGA-1/status

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=49789

--- Comment #1 from Harald Judt <h.judt@gmx.at> 2012-05-11 04:38:17 PDT ---
Created attachment 61442
  --> https://bugs.freedesktop.org/attachment.cgi?id=61442
xdpyinfo

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[Bug 49789] External monitor flickers on xrandr or cat /sys/class/drm/card0-VGA-1/status

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=49789

Alex Deucher <agd5f@yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |NOTABUG

--- Comment #2 from Alex Deucher <agd5f@yahoo.com> 2012-05-11 07:50:48 PDT ---
The driver uses load detection to see if a monitor is connected if it does not
provide an EDID.  The process of detecting load on the pins will cause a
momentary distortion of the image in some cases.  There's not much else you can
do if you want to be able to detect the presence or lack of a monitor without
an EDID.  BTW, for monitors with an EDID the driver will automatically generate
events when they are connected or disconnected so there is no need to poll. 
Unfortunately, load detection is the only option for analog monitors that have
no EDID.  Digital monitors will generate a hotplug interrupt.

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[Bug 49789] External monitor flickers on xrandr or cat /sys/class/drm/card0-VGA-1/status

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=49789

--- Comment #3 from Harald Judt <h.judt@gmx.at> 2012-05-11 08:10:30 PDT ---
Can I somehow find out (log files, whatever), whether the monitor has an EDID
or not, after it has been connected? Because then I could turn off the polling
for the time being, or at least reduce the polling interval.

With regard to the events: I've tried using udev to react to the hotplug
events, but it wouldn't work reliably. It would successfully recognize a
monitor the first time, but fail to trigger on disconnect or later connect
attempts. So unfortunately, my approach was and probably is the only
viable/reliable here to do it automatically.

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[Bug 49789] External monitor flickers on xrandr or cat /sys/class/drm/card0-VGA-1/status

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=49789

--- Comment #4 from Alex Deucher <agd5f@yahoo.com> 2012-05-11 10:23:56 PDT ---
(In reply to comment #3)
> Can I somehow find out (log files, whatever), whether the monitor has an EDID
> or not, after it has been connected? Because then I could turn off the polling
> for the time being, or at least reduce the polling interval.
> 

You can check the `xrandr --verbose` output.

> With regard to the events: I've tried using udev to react to the hotplug
> events, but it wouldn't work reliably. It would successfully recognize a
> monitor the first time, but fail to trigger on disconnect or later connect
> attempts. So unfortunately, my approach was and probably is the only
> viable/reliable here to do it automatically.

What kernel are you using?  There were some problems with disconnects not
getting detected in certain cases with that were fixed in 3.3 IIRC.

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[Bug 49789] External monitor flickers on xrandr or cat /sys/class/drm/card0-VGA-1/status

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=49789

--- Comment #5 from Harald Judt <h.judt@gmx.at> 2012-05-15 02:01:59 PDT ---
(In reply to comment #4)
> (In reply to comment #3)
> > Can I somehow find out (log files, whatever), whether the monitor has an EDID
> > or not, after it has been connected? Because then I could turn off the polling
> > for the time being, or at least reduce the polling interval.
> > 
> 
> You can check the `xrandr --verbose` output.

Thanks, that will help.

> > With regard to the events: I've tried using udev to react to the hotplug
> > events, but it wouldn't work reliably. It would successfully recognize a
> > monitor the first time, but fail to trigger on disconnect or later connect
> > attempts. So unfortunately, my approach was and probably is the only
> > viable/reliable here to do it automatically.
> 
> What kernel are you using?  There were some problems with disconnects not
> getting detected in certain cases with that were fixed in 3.3 IIRC.

I've tried again with 3.4.0-rc7, but nothing changed. This is on a different
system though, so I filed another bug #49943.

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