Re: PROBLEM: i915 Haswell KMS wrong maximum resolution

[Jani Nikula <jani.nikula@linux.intel.com>]

On Sun, 30 Mar 2014, Kenneth de Mello <kdemello1980@gmail.com> wrote:
> What about dual-link DVI?   I though the additional link addressed the
> pixel clock limitation.   Has it only been using a single link this entire
> time, and it's only worked by ignoring the maximum dotclock, so in other
> words, the fact it works at all is the bug?
>
> Also, the commit that rejects mode exceeding 165MHz states:
>
>     "Single-link DVI max dotclock is 165MHz. Filter out modes with higher
>      dotclock when the monitor doesn't support HDMI."
>
> Does this mean HDMI in general?   This monitor does support HDMI, but the
> maximum resolution when using the physical HDMI ports is 1920x1080.
>
> What is the solution here, to switch to displayport if I want to use kernel
> 3.13.7 and beyond?   (This is fine, I just need to know so I can buy the
> cable).

For further details please see the bug report [1].

The reason for the change was that modes with higher than 165 MHz
dotclock are invalid for single-link DVI. We don't support dual-link DVI
natively. Thus this is about HDMI->DVI adapters which are either
dual-link DVI (Ville says highly unlikely) or single-link DVI that allow
higher than 165 MHz dotclock in the monitor end. I'm not sure how we
could distinguish that from a regular single-link DVI that *is* bound by
the maximum dotclock.

Product details for the adapter you're using might be interesting.

BR,
Jani.



[1] https://bugzilla.kernel.org/show_bug.cgi?id=72961


-- 
Jani Nikula, Intel Open Source Technology Center