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@xxxxxxxxxxxxxxx> wrote:
On Mon, 18 Sep 2017, Maxim Levitsky <maximlevitsky@xxxxxxxxx> 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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