[Nouveau] Quadro 4000 with iiyama B2783QSU should be 2560x1440 but detected as 1920x1080. [SOLVED]

[Roger Price]

On Wed, 21 Sep 2016, Ilia Mirkin wrote:

> I think you want the reduced blanking modeline:
>
> $ cvt -r 2560 1440
> # 2560x1440 59.95 Hz (CVT 3.69M9-R) hsync: 88.79 kHz; pclk: 241.50 MHz
> Modeline "2560x1440R"  241.50  2560 2608 2640 2720  1440 1443 1448
> 1481 +hsync -vsync
>
> This matches your monitor's detailed timings:
>
> [    55.220] (II) NOUVEAU(0): Supported detailed timing:
> [    55.220] (II) NOUVEAU(0): clock: 241.5 MHz   Image Size:  597 x 336 mm
> [    55.220] (II) NOUVEAU(0): h_active: 2560  h_sync: 2608  h_sync_end
> 2640 h_blank_end 2720 h_border: 0
> [    55.220] (II) NOUVEAU(0): v_active: 1440  v_sync: 1443  v_sync_end
> 1448 v_blanking: 1481 v_border: 0
>
> Not sure why a 2560x1440 modeline isn't being advertised in EDID -
> perhaps the monitor is in some "safe" setting where that's not
> reported? Might have to flip it into DP 1.2 mode or something.

I tried the reduced blanking modeline, but the 1920x1080 format persisted. 
So I then replaced the display port cables with the cables labelled "DP 
V1.2" supplied by iiyama with the monitors.  This fixed the problem. I now 
have 2560x1440R on two iiyama monitors.  I was most agreably surprized 
that the nouveau driver automatically placed DP-2 to the right of DP-1 to 
form a 5120x1440 surface.  Very polished execution by nouveau!

Thanks for your help, Roger