Comment 121 for bug 1522922
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#121 |
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67d34a1
(Get the code!)
(In reply to alex from comment #112)
> (In reply to Mika Kahola from comment #110)
> > (In reply to alex from comment #109)
> > > Dammit. Now this regression has made it into the LTS kernel. Are you guys
> > > kidding me? Is it not possible for the changes that caused this
> > > exceptionally annoying regression (as in my computer is now almost entirely
> > > unusable) to be removed from the current production kernel, pending a proper
> > > fix?????
> >
> > My current understanding is that there are multiple causes for flickering.
> > Reverting this patch may solve an issue with one platform. Could you share
> > your dmesg log with drm.debug=0x1e for further analysis, please.
>
> Posted. I rebooted into the stock 4.5.1 kernel (direct from the Arch
> repository) with drm.debug=0x1e added to the kernel command line, logged in,
> suspended, resumed, and dumped the log with journalctl. I took a quick
> check through and didn't see any messages that indicated any sort of failure
> after the suspend operation. However there are a lot of messages in there,
> so I could have missed something. What I do know is that after the resume
> from suspend, I get something on the order of a 2 Hz flicker on the display
> that looks like the eDP link is flapping - i.e. there is tearing that
> affects the bottom portion of the display more than the top due to the link
> going down in the middle of a frame, portions of the display are briefly
> distorted or colored strangely, etc. None of this happens on 4.1.21, which
> is where I will stay until this gets a proper fix in the mainline.
It seems that you have similar issue than we have seen before. During resume, the display driver tries to use the DP link parameters that was computed during the initial boot. However, the clock recovery is not obtained and hence the DP link is retrained. At this stage, the driver tries with 0 voltage swing and no pre-emphasis. For some reason the clock recovery is obtained and the DP link is set up with lower voltage swing and pre-emphasis settings than after the initial boot.
I suggest that you try all these 4 patches on top of the drm-intel-nightly and report back if this set provides a fix or not
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