[Intel-gfx] Issues withddcutils/ddccontorl remote control of an monitor with Skylake/Kabylake GPU

[Maxim Levitsky]

I'll do this soon. Meanwhile I bought another HDMI cable, one that supports
4K (and thus should be better electrically) and I see much less i2c errors
to the point that monitor control works about 95% of the time.
I do see plenty of i2c errors still and sometimes still the control fails.

I strongly suspect that too high i2c clock is used. Is there a way to tweak
GMBUS clock?
I will soon compile the kernel (still stuck at stock 4.12 kernel) and see
if I can tweak the driver. I see for instance that it can use bit-banging
instead, so maybe I will force this.

Best regards,
       Maxim Levitsky

On Mon, Sep 18, 2017 at 11:46 AM, Jani Nikula <jani.nikula at linux.intel.com>
wrote:

> On Mon, 18 Sep 2017, Maxim Levitsky <maximlevitsky at gmail.com> wrote:
> > I have a Kabylake GPU (i7700K) and I can't control my monitor with it
> using
> > ddcutil.
> > It only sometimes work and most of the time spews i2c errors.
> > I also tested on my laptop which has Skylake GPU and I see the same
> issue.
> > The same monitor works with my nvidia GPU and when connected via VGA<->DP
> > adapter to the notebook.
> >
> > I will soon provide all the debug logs i could gather, but meanwhile
> maybe
> > this is known issue?
> >
> > For reference I used 4.12 kernel on the Kabylake GPU.
>
> Please file bugs at [1], and attach the logs there. ISTR there have been
> bugs reported about this before, but I couldn't find any. It certainly
> has never been a high priority thing.
>
> BR,
> Jani.
>
>
> [1] https://bugs.freedesktop.org/enter_bug.cgi?product=DRI&
> component=DRM/Intel
>
>
> --
> Jani Nikula, Intel Open Source Technology Center
>
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