Bug 84083

What does xrandr --verbose report before unplugging, after and then after plugging it back in?

Created attachment 106985 [details]
xrandr --verbose before plugging

(In reply to comment #1)
> What does xrandr --verbose report before unplugging, after and then after
> plugging it back in?

Please check the attachment.

Created attachment 106986 [details]
xrandr --verbose plugging

Created attachment 106987 [details]
xrandr --verbose after unpluging

Your userspace desktop environment didn't respond to the hotplug notification and so did not extend the desktop onto the new output. Kernel/xrandr looks fine so I don't this is a bug, or at least those snapshots are behaving as expected.

0e32b39ceed665bfa4a77a4bc307b6652b991632 is the first bad commit
Author:     Dave Airlie <airlied@redhat.com>
AuthorDate: Fri May 2 14:02:48 2014 +1000
Commit:     Dave Airlie <airlied@redhat.com>
CommitDate: Tue Jul 22 11:20:26 2014 +1000


    drm/i915: add DP 1.2 MST support (v0.7)

    This adds DP 1.2 MST support on Haswell systems.

    Notes:
    a) this reworks irq handling for DP MST ports, so that we can
    avoid the mode config locking in the current hpd handlers, as
    we need to process up/down msgs at a better time.

    Changes since v0.1:
    use PORT_PCH_HOTPLUG to detect short vs long pulses
    add a workqueue to deal with digital events as they can get blocked on the
    main workqueue beyong mode_config mutex
    fix a bunch of modeset checker warnings
    acks irqs in the driver
    cleanup the MST encoders

    Changes since v0.2:
    check irq status again in work handler
    move around bring up and tear down to fix DPMS on/off
    use path properties.

    Changes since v0.3:
    updates for mst apis
    more state checker fixes
    irq handling improvements
    fbcon handling support
    improved reference counting of link - fixes redocking.

    Changes since v0.4:
    handle gpu reset hpd reinit without oopsing
    check link status on HPD irqs
    fix suspend/resume

    Changes since v0.5:
    use proper functions to get max link/lane counts
    fix another checker backtrace - due to connectors disappearing.
    set output type in more places fro, unknown->displayport
    don't talk to devices if no HPD asserted
    check mst on short irqs only
    check link status properly
    rebase onto prepping irq changes.
    drop unsued force_act

    Changes since v0.6:
    cleanup unused struct entry.

    [airlied: fix some sparse warnings].

    Reviewed-by: Todd Previte <tprevite@gmail.com>
    Signed-off-by: Dave Airlie <airlied@redhat.com>

:040000 040000 93e1ede3cbc00222af2880adafbd633f5b9fd4e5 19d739b7d711dfeebb5335d34dd43f15f1295be2 M      drivers

The commit unable to revert

I found the first bad commit about this failure. Maybe enable DP 1.2 MST causes this failure.

(In reply to comment #2)
> Created attachment 106985 [details]
> xrandr --verbose before plugging
> 
> (In reply to comment #1)
> > What does xrandr --verbose report before unplugging, after and then after
> > plugging it back in?
> 
> Please check the attachment.

Here, did you actually meant that this xrandr was with the DP monitor still attached, i.e. before *unplugging*?

If so, since the detection at this point declares that DP1 is unconnected, the bug is that we don't detect the display until after we plug it back in.

(In reply to comment #8)
> (In reply to comment #2)
> > Created attachment 106985 [details]
> > xrandr --verbose before plugging
> > 
> > (In reply to comment #1)
> > > What does xrandr --verbose report before unplugging, after and then after
> > > plugging it back in?
> > 
> > Please check the attachment.
> 
> Here, did you actually meant that this xrandr was with the DP monitor still
> attached, i.e. before *unplugging*?
> 
> If so, since the detection at this point declares that DP1 is unconnected,
> the bug is that we don't detect the display until after we plug it back in.

xrandr --verbose before plugging：DP monitor didn't attach.
xrandr --verbose plugging: DP monitor attached
xrandr --verbose after unpluging: DP monitor didn't attach

(In reply to Guo Jinxian from comment #9)
> (In reply to comment #8)
> > (In reply to comment #2)
> > > Created attachment 106985 [details]
> > > xrandr --verbose before plugging
> > > 
> > > (In reply to comment #1)
> > > > What does xrandr --verbose report before unplugging, after and then after
> > > > plugging it back in?
> > > 
> > > Please check the attachment.
> > 
> > Here, did you actually meant that this xrandr was with the DP monitor still
> > attached, i.e. before *unplugging*?
> > 
> > If so, since the detection at this point declares that DP1 is unconnected,
> > the bug is that we don't detect the display until after we plug it back in.
> 
> xrandr --verbose before plugging：DP monitor didn't attach.
> xrandr --verbose plugging: DP monitor attached
> xrandr --verbose after unpluging: DP monitor didn't attach

Everything seems to work. Is this _really_ with a broken kernel?

With mst connectors go away, maybe this is it? Since the connector wont be there we can restore the mode magically in the kernel

In that case this is wontfix ... at least according to Dave Airlie.

(In reply to Daniel Vetter from comment #10)
> (In reply to Guo Jinxian from comment #9)
> > (In reply to comment #8)
> > > (In reply to comment #2)
> > > > Created attachment 106985 [details]
> > > > xrandr --verbose before plugging
> > > > 
> > > > (In reply to comment #1)
> > > > > What does xrandr --verbose report before unplugging, after and then after
> > > > > plugging it back in?
> > > > 
> > > > Please check the attachment.
> > > 
> > > Here, did you actually meant that this xrandr was with the DP monitor still
> > > attached, i.e. before *unplugging*?
> > > 
> > > If so, since the detection at this point declares that DP1 is unconnected,
> > > the bug is that we don't detect the display until after we plug it back in.
> > 
> > xrandr --verbose before plugging：DP monitor didn't attach.
> > xrandr --verbose plugging: DP monitor attached
> > xrandr --verbose after unpluging: DP monitor didn't attach
> 
> Everything seems to work. Is this _really_ with a broken kernel?

After unplug/plug, xrandr is able to detect DP monitor, but x unable to light up, we think it's a bug for end user. If kill x then start x, the x works well.

(In reply to Daniel Vetter from comment #11)
> With mst connectors go away, maybe this is it? Since the connector wont be
> there we can restore the mode magically in the kernel
> 
> In that case this is wontfix ... at least according to Dave Airlie.

Sorry, I don't understand you exactly. Could you tell us what should we do? Thanks.

DP MST replugging doesn't work, that's just how it is.

We could try to fix that up, but it would be massive amounts of work. So should be tracked in JIRA and needs people actually working on in.

Close it, since developer think it a to-do task and track it on Jira.

while to track the work in Jira, let's keep this bug open here.

*** Bug 86237 has been marked as a duplicate of this bug. ***

Marking as wontfix again.

reopening with severity=enhancement.

Close this since 3.18 stable has that fix.

Closing old verified.