linux-kernel - Re: [REGRESSION] i915: No HDMI output with 4.4

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Date:	Tue, 16 Feb 2016 13:54:09 +0100
From:	Daniel Vetter <daniel@...ll.ch>
To:	Oleksandr Natalenko <oleksandr@...alenko.name>
Cc:	Ville Syrjälä 
	<ville.syrjala@...ux.intel.com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Sonika Jindal <sonika.jindal@...el.com>,
	Shashank Sharma <shashank.sharma@...el.com>,
	Gary Wang <gary.c.wang@...el.com>
Subject: Re: [REGRESSION] i915: No HDMI output with 4.4

On Tue, Feb 16, 2016 at 12:58:56PM +0200, Oleksandr Natalenko wrote:
> Ville, Daniel,
> 
> I've just got another monitor and another DVI-HDMI cable, and here what I've
> got.
> 
> ===Single Link DVI-D cable with 3 different monitors===
> 
> Computer DVI ——— DVI-D (Single Link)/HDMI cable ——— HDMI LG 23MP65HQ-P ===
> not working

I presume the above LG screen is what you've called previously "old
monitor"?

> Computer DVI ——— DVI-D (Single Link)/HDMI cable ——— HDMI LG 23MP67HQ-P ===
> not working
> Computer DVI ——— DVI-D (Single Link)/HDMI cable ——— HDMI LG 23MP55HQ-P ===
> works!
> 
> ===Dual Link DVI-D cable with monitor that doesn't work with Single Link
> cable===
> 
> Computer DVI ——— DVI-D (Dual Link)/HDMI cable ——— HDMI LG 23MP65HQ-P ===
> works!

Funky. Can you pls grab the debug logs (with the special patches from
Ville) for this case? I wonder why suddenly different cable and it works.

Also: Is this one of these older-ish screens where you must have a
dual-link cable to drive it at full resolution&refresh rate?
-Daniel


> ===Laptop with HDMI output===
> 
> Laptop HDMI ——— HDMI/HDMI cable ——— HDMI LG 23MP65HQ-P === works!
> 
> I'd say that single link DVI cables are broken with new kernel, but one of
> monitors could work with such a cable. So I have no idea :(.
> 
> Regards,
>   Oleksandr.
> 
> 15.02.2016 17:42, Daniel Vetter wrote:
> >The other downside is that it'll make us non-compliant, which was the
> >point of this entire ordeal: HDMI spec forbids us from starting any i2c
> >transactions when the hpd isn't signalling a present screen.
> >
> >So maybe we need to buy one of these broken screens.
> >
> >Oleksandr, what exact model are you using? And any chance that you could
> >test this on some other machine with intel gfx and latest kernel, just to
> >make sure this really is some issue with the sink and not with the machine
> >itself? And I guess you've tested with some other hdmi sink, and that
> >works?

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch