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Date: Sat, 18 Nov 2017 13:51:00 +0100
From: Greg KH <gregkh@linuxfoundation.org>
To: Rainer Fiebig <jrf@mailbox.org>
Cc: stable@vger.kernel.org
Subject: Re: 4.9.62: intermittent flicker after upgrade from 4.9.61
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On Sat, Nov 18, 2017 at 01:47:32PM +0100, Rainer Fiebig wrote:
> Hi!
> 
> Hopefully the right addressee.
> 
> Encountered two bad backports which cause screen-flicker.
> dmesg shows:
> 
> ...
> [drm:ironlake_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun
> [drm:ironlake_irq_handler [i915]] *ERROR* PCH transcoder A FIFO underrun
> [drm:ironlake_irq_handler [i915]] *ERROR* CPU pipe B FIFO underrun
> [drm:ironlake_irq_handler [i915]] *ERROR* PCH transcoder B FIFO underrun
> ...
> 
> CPU: Intel Core i3 (Clarkdale/Ironlake)
> 
> The backports are:
> 
> - diff --git a/drivers/gpu/drm/i915/intel_pm.c
> b/drivers/gpu/drm/i915/intel_pm.c
>     index 49de476..277a802 100644
> - diff --git a/drivers/gpu/drm/i915/intel_drv.h
> b/drivers/gpu/drm/i915/intel_drv.h
>     index a19ec06..3ce9ba3 100644
> 
> After reversing them the flicker is gone, no more messages in dmesg. All
> else OK so far.

So which commit was the one that caused the problem?  I will be glad to
revert it.

thanks,

greg k-h