Re: brix pro + dell UP3214Q, 3840x2160 @ 60 Hz

[Kenneth Johansson <ken@kenjo.org>]

On 2014-03-05 00:44, Damien Lespiau wrote:
> On Tue, Mar 04, 2014 at 09:38:40PM +0100, Kenneth Johansson wrote:
>> On 2014-03-04 17:12, Jani Nikula wrote:
>>> On Tue, 04 Mar 2014, Kenneth Johansson <ken@kenjo.org> wrote:
>>>> So I have a brix pro that is a i7 4700R with Intel Iris Pro Graphics 5200.
>>>> and I 4k display from dell that can do 3840 x 2160  at 60 Hz (DP1.2)
>>>>
>>>> So both end should be ok. But when I try daily build of ubuntu as of
>>>> yesterday all I get is 3840 x 2160 at 30Hz. I really hope this is just
>>>> some software thing as 30Hz is not usable but the display is really
>>>> crisp so I relly relly dont want to have to return it.
>>>>
>>>> I also noticed that when I go to console mode something gets configured
>>>> wrong. I do get picture but the kernel manage to get the dimensions
>>>> wrong so several 3-4 lines of the console is below the bottom and can't
>>>> be seen.
>>> Please try drm-intel-nightly branch of [1]. It has the code to enable
>>> higher frequencies for DP 1.2:
>> Tried that same result. I turned on drm.debug=0x4 but for me the
>> only thing I can see is that the 60Hz mode is not in the list
> The EDID doesn't even list the 4k@60 fps mode, to me, this looks like it
> may be of those monitors that need DP 1.2 MST to work (a feature we
> don't have implemented in the kernel and that needs quite a bit of
> work). It could be a totally wrong guess though, what monitor are we
> talking about?
It's in the subject line :)

http://accessories.us.dell.com/sna/productdetail.aspx?c=us&cs=04&l=en&sku=210-ACBL

I can't see anything about MST on the spec tab on the website.
the only thing is that you have to use DP1.2 for 60Hz.

the note on that line is.
---------
In order to display the 3840x2160 at 60 Hz. native resolution, please 
ensure the graphics card and its drivers used on the PC/Laptop is 
capable of supporting up to 3840x2160 at 60 Hz. resolution. All of the 
UP3214Q ports (DP, Mini-DP and HDMI) can support 3840x2160 resolution. 
The PC/Laptop must be HDMI 1.4 compliant.
---------

what exactly needs to be done to support MST in the kernel ? from what I 
understand googling is that if a monitor needs MST it looks to the 
computer like it was two monitors instead of just one. But is this 
something that is just fixable in software on the computer side ? It 
feels like supporting multiple streams is something that needs to be 
done in some hardware muxer.