DP1.2 MST HUB

Tue Dec 4 02:31:24 UTC 2018

+People in community.

Rodrigo,

Thanks for the kind info.

What's the answer to below question?

I find i915 binds one pipeline per display. It means even with DP1.2 MST, i915 driver still restricts the display number to the display pipeline
number. Am I right?

In addition, I might mislead you at case 1).  The NUC has 1 HDMI interface and 1 USB type-C interface. I connect a display by HDMI to that HDMI interface. Then, I connect other 2 displays by the CE-LINK box which connect to the usb type-C interface.

Yanmin

> -----Original Message-----
> From: Vivi, Rodrigo
> Sent: Tuesday, December 04, 2018 6:28 AM
> To: Zhang, Yanmin <yanmin.zhang at intel.com>
> Cc: Syrjala, Ville <ville.syrjala at intel.com>
> Subject: Re: DP1.2 MST HUB
> 
> Hi there,
> 
> again, please ask these questions in public mailing lists.
> 
> On Sun, Dec 02, 2018 at 06:43:31PM -0800, Zhang, Yanmin wrote:
> > Here is the result.
> >
> > 1) If I use a CE-LINK 1-to-2 converter, 1usb type-C in, and 2 HDMI out, it works
> with my NUC. This NUC has 1 HDMI and 1 USB type C interfaces.
> > 	a) If I connect 1 display by HDMI, and other 2 displays by the CE-LINK,
> android refuses (logcat shows No permission) to show application GUI to the 3rd
> display. It might be an issue of Android.
> > 	b) If I remove HDMI display, but just connect other 2 displays by CE-LINK,
> both displays can work.
> >
> > 2) If I use CLUB-3D box which has 1 DP in and 4 DP out, I have to use a usb type-
> C to DP cable, then connect to a DP converter with 2 daughter interfaces, then
> connect to the CLUB-3D, then to 2 displays. Kernel driver reports the displays, but
> the display is always black. Perhaps there are too many converters on the
> connection path.
> > If I use CLUB-3D box to connect to my desktop which uses NEVIDE display card,
> it works well.
> >
> >
> > At 1).b) case, I find i915 binds one pipeline per display. It means even with
> DP1.2 MST, i915 driver still restricts the display number to the display pipeline
> number. Am I right? Can we extend display number more than pipeline number?
> 
> I'm not sure if I followed your case here, but 2 things here:
> 
> 1. it seems that
> you might be reached the maximun number of allocated vcpi here.
> 
> Just by leaving cable connected the vpci gets reserved on drm if I remember
> correctly so things might not fully work.
> 
> But it is hard to tell without any log. if that is the case.
> 
> 2. About the "extend display part" there is currently a limitation of the vertical
> size that Ville was working to solve that.
> I'm not sure about the status.
> 
> Thanks,
> Rodrigo.
> 
> >
> > Thanks,
> > Yanmin
> >
> > > -----Original Message-----
> > > From: Zhang, Yanmin
> > > Sent: Friday, November 30, 2018 8:24 AM
> > > To: Vivi, Rodrigo <rodrigo.vivi at intel.com>
> > > Cc: Syrjala, Ville <ville.syrjala at intel.com>
> > > Subject: RE: DP1.2 MST HUB
> > >
> > > Rodrigo,
> > >
> > > Thanks for the kind info. 'enabling' here is to check if DP1.2 MST
> > > (perhaps with
> > > HBR2) can work with intel NUC (with type-C DP). Later on, check it
> > > on new IVE system which might be based on ElkhartLake or Tigerlake.
> > > If it doesn't work, I have to check if it's about either MST HUB
> > > hardware, or software such like i915 driver. Basically, I am not
> > > i915 driver expert, but I assume you guys already enabled it well.
> > >
> > > I already ordered a MST HUB https://www.club-
> > > 3d.com/en/detail/2411/multi_stream_transport_(mst)_hub_displayportt_
> > > 1.2_qu ad_monitor/, and another one which has an input of USB Type-C
> > > and 2 HDMI outputs.
> > > Hope it can work.
> > >
> > > Even when it works, IVE system might not use the MST HUB directly. I
> > > suppose IVE hardware architect will use specific AIC to implement
> > > MST HUB capability on board. Currently, I want to prove DP 1.2 MST can work
> well on Intel chips.
> > >
> > > I will keep you guys posted.
> > >
> > > Yanmin
> > >
> > > > -----Original Message-----
> > > > From: Vivi, Rodrigo
> > > > Sent: Friday, November 30, 2018 1:45 AM
> > > > To: Zhang, Yanmin <yanmin.zhang at intel.com>
> > > > Cc: Syrjala, Ville <ville.syrjala at intel.com>
> > > > Subject: Re: DP1.2 MST HUB
> > > >
> > > > Hi Yanmin,
> > > >
> > > > On Wed, Nov 28, 2018 at 05:03:02PM -0800, Zhang, Yanmin wrote:
> > > > >    Dear GFX/display experts,
> > > >
> > > > maybe it would be probably good to ask to dri-devel and/or
> > > > intel-gfx at lists.freedesktop.org
> > > >
> > > > >
> > > > >
> > > > >    Would you like to share some info about MST HUB? I am enabling
> multiple
> > > > >    display support by MST.
> > > >
> > > > What do you mean by "enabling" here?
> > > >
> > > > >
> > > > >
> > > > >    1)      Currently, I have a KBL NUC which has a USB-Type C port. By a
> > > > >    USB Type-C to DP cable, it connect to a display panel and it can work
> > > > >    well. KBL NUC prod spec says it can extend to connect multiple displays
> > > > >    by DP1.2 MST. What MST HUB should be used?
> > > >
> > > > short answer: Any dongle that supports DP1.2 MST.
> > > >
> > > > However dongles can have firmware doing non compliant things that
> > > > could cause headaches. So I'd recommend to get one that is know to
> > > > have a
> > > good quality.
> > > > Unfortunately I don't have any one specific to recommend.
> > > >
> > > > >
> > > > >    2)      If I buy a HUB like
> > > > >
> > > >
> > > [1]https://item.taobao.com/item.htm?spm=a230r.1.14.110.32f348d5JPpMM
> > > s&
> > > > i
> > > > >    d=43812089455&ns=1&abbucket=17#detail , can I use that type-C to DP
> > > > >    conversion cable to connect to the HUB and MST still works?
> > > > >
> > > > >    How about [2]http://item.jd.com/10210412498.html?
> > > > >
> > > > >
> > > > >    3)      Can I use another simple HUB like
> > > > >    [3]http://item.jd.com/28683591806.html?
> > > > >
> > > > >
> > > > >    Above links have Chinese characters, but the pictures and some English
> > > > >    text are clear.
> > > >
> > > > Well, first link doesn't work and I couldn't extract any useful
> > > > information from the english parts. But if they implement DP MST
> > > > properly it
> > > should just work.
> > > >
> > > > >
> > > > >
> > > > >    Would you like to give me your expert comments on that?
> > > >
> > > > try it out and let me know if it works :P
> > > >
> > > > Cheers,
> > > > Rodrigo.
> > > >
> > > > >
> > > > >
> > > > >    Thanks,
> > > > >
> > > > >    Yanmin
> > > > >
> > > > > References
> > > > >
> > > > >    1.
> > > >
> > > https://item.taobao.com/item.htm?spm=a230r.1.14.110.32f348d5JPpMMs&i
> > > d=
> > > > 4
> > > > 3812089455&ns=1&abbucket=17#detail
> > > > >    2. http://item.jd.com/10210412498.html
> > > > >    3. http://item.jd.com/28683591806.html