[Intel-gfx] [PATCH 0/3] HDMI optimization series

[Daniel Vetter]

On Mon, Aug 10, 2015 at 02:05:47PM +0530, Jindal, Sonika wrote:
> 
> 
> On 8/10/2015 1:38 PM, Daniel Vetter wrote:
> >On Mon, Aug 10, 2015 at 04:50:37AM +0000, Jindal, Sonika wrote:
> >>Hi Daniel,
> >>
> >>That patch was already merged:
> >>http://lists.freedesktop.org/archives/intel-gfx/2015-July/071142.html
> >>
> >>For SKL, the above patch helped in getting the correct ISR bits set.
> >>One option is to enable the HDMI optimization from VLV onwards.
> >>I don't have an ivb machine to try out the issue.
> >
> >ivb is simple the machine I have here, but when we tried this the last
> >time around we had reports for all platforms (your patch still doesn't
> >cite the relevant sha1 btw). I think there are 3 possible explanations:
> >
> Yes, I don't know which were those patches and how to find them..

git blame (recursively) and git log on intel_hdmi.c will tell you the
story. I require all these extensive git commit messages because I dig
them out daily. Also git log --pickaxe (well I use the equivalent in the
gitk gui). If these tools are generally unknown in the vpg display team
then we absolutely need to do a training session about them, they're
extremely powerful and useful to dig out the history of the i915 code.

> >a) we do something wrong with hpd handling on these platforms. That seems
> >to be the explanation you favour (with the gen >= 7 checks and all that),
> >but I think it's very unlikely: On each platform where we had reports of
> >hpd being broken there was also machines where hpd works perfectly fine.
> >
> Not sure, I will find one ivb system and try on that.
> 
> >b) There's broken HDMI (or DVI) sinks out there. If that's the case we can
> >never merge your patch.
> I doubt this because we have tested these patches with many sinks in the
> past with VLV/CHV.
> >
> >c) There's something in vbt or somewhere else that tells the windows
> >driver whether using hpd or not is ok (and the hpd problem is actually an
> >issue with certain OEM machines ...).
> >
> No, nothing like that.
> 
> >I hoped that with your hpd handling fix we'd have some indication that our
> >hpd troubles are of type a). But since I tested with your patch that
> >didn't work out.
> >
> >And until we have some evidence that our hpd troubles aren't type b) I
> >really don't want to merge any patch which relies upon hpd bits for hdmi.
> >-Daniel
> >
> I will try on ivb.

I don't think it's ivb specific, since we do have ivb machines where hpd
works perfectly fine. Same for every other platform. The only thing which
seems common is that DP+ connectors work, but some of the hdmi-only
connectors fail. That's why I wondered whether there's something i915 does
different than the windows driver. In case you can get hold of one, the
broken laptop I have here is an Asus UX31A with ivb.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch