Blank screen at 4k/60hz

[jadbox]

I think I shot myself in the foot being an early adopter of 4k, but maybe someone else has figured it out.
Here's the rundown:

Nvidia driver: 343.22 on Debian Jessie
Card: 980gtx with high-speed hdmi 2 cable | Display: 4k/60hz compatible Sony xbr49x850b

Using the NVidia panel to set 3840x2160 or 4k at 60hz: blank screen (but works in Win8)
Forcing the above resolution with xrandr --ouput also causes a blank screen.
Same resolutions at 30hz: works

The nvidia display panel and xrandr shows 4k/60hz as a valid option:
HDMI-0 connected primary 3840x2160+0+0 (normal left inverted right x axis y axis) 1080mm x 610mm
1920x1080 60.00 + 59.94 59.93 29.97 23.97 60.05 60.00
4096x2160 59.94 24.00 23.98
3840x2160 59.94 29.97* 25.00 23.98
[[...]]

I've tried making a custom mode in xrandr using CVT, but I always get a Mismatch Error regardless of refresh rate specified:
cvt 3840 2160 59.94 #also tried with just 60hz here with same result
3840x2160 59.92 Hz (CVT) hsync: 134.04 kHz; pclk: 712.00 MHz
Modeline "3840x2160_59.94" 712.00 3840 4160 4576 5312 2160 2163 2168 2237 -hsync +vsync
xrandr --newmode "3840x2160_59.94" 712.00 3840 4160 4576 5312 2160 2163 2168 2237 -hsync +vsync
xrandr --addmode HDMI-0 "3840x2160_59.94"
X Error of failed request: BadMatch (invalid parameter attributes) Major opcode of failed request: 140 (RANDR) Minor opcode of failed request: 18 (RRAddOutputMode) Serial number of failed request: 47 Current serial number in output stream: 48

xrandr --current Screen 0: minimum 8 x 8, current 3840 x 2160 [[30hz]], maximum 16384 x 16384

Any ideas on what to do? Again, I'm having no issues with Win8 at this res/refresh.

EDIT, more info:
lspci -v
01:00.0 VGA compatible controller: NVIDIA Corporation Device 13c0 (rev a1) (prog-if 00 [VGA controller])
Subsystem: NVIDIA Corporation Device 1116
Flags: bus master, fast devsel, latency 0, IRQ 61
Memory at f6000000 (32-bit, non-prefetchable) [size=16M]
Memory at e0000000 (64-bit, prefetchable) [size=256M]
Memory at f0000000 (64-bit, prefetchable) [size=32M]
I/O ports at e000
[virtual] Expansion ROM at f7000000 [disabled] [size=512K]
Capabilities: <access denied>
Kernel driver in use: nvidia

Xorg.conf:
Section "ServerLayout"
Identifier "Layout0"
Screen 0 "Screen0" 0 0
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "Mouse0" "CorePointer"
Option "Xinerama" "0"
EndSection

Section "Files"
EndSection

Section "InputDevice"
# generated from default
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/psaux"
Option "Emulate3Buttons" "no"
Option "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
# generated from default
Identifier "Keyboard0"
Driver "kbd"
EndSection

Section "Monitor"
Identifier "Monitor0"
VendorName "Unknown"
ModelName "SONY TV *06"
HorizSync 14.0 - 140
VertRefresh 22.0 - 62
Option "DPMS"
EndSection

Section "Device"
Identifier "Device0"
Driver "nvidia"
Option "Coolbits" "1"
Option "AddARGBGLXVisuals" "true"
VendorName "NVIDIA Corporation"
BoardName "GeForce GTX 980"
Option "ExactModeTimingsDVI" "true"
EndSection

Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
Option "Stereo" "0"
Option "metamodes" "3840x2160_30 +0+0; nvidia-auto-select +0+0"
Option "SLI" "Off"
Option "MultiGPU" "Off"
Option "BaseMosaic" "off"
SubSection "Display"
Option "ColorSpace" "YCbCr444"
Depth 24
Modes "3840x2160_60.00" "3840x2160" "1920x1080"
EndSubSection
EndSection

Section "Extensions"
Option "Composite" "enable" # also tried this as disabled
EndSection

[jadbox]

Under Win8, the timings reported in the nvidia settings are:
H V
3840 2160
front porch: 176 8
Sync width: 88 10
total: 4400 2250
Polarity: + +
Refresh: 135.00 60.00
Pixel clock: 594.00mhz

I've tried then setting the modeline in xorg.conf:
Option "UseEdidFreqs" "False"
Modeline "4k" 594.0 3840 4016 4104 4400 2160 2168 2178 2250 +hsync +vsync

The result is still a blank screen sadly. The xorg logs states that it activated mode "4k" without error.

[jadbox]

From XRANDR --verbose:

HDMI-0 connected primary 1920x1080+0+0 (0x169) normal (normal left inverted right x axis y axis) 1085mm x 610mm
Identifier: 0x168
Timestamp: 1593291
Subpixel: unknown
Gamma: 1.0:1.0:1.0
Brightness: 1.0
Clones:
CRTC: 0
CRTCs: 0 1 2 3
Transform: 1.000000 0.000000 0.000000
0.000000 1.000000 0.000000
0.000000 0.000000 1.000000
filter:
EDID:
00ffffffffffff004dd9038c01010101
01180103806c3d780a0dc9a057479827
12484c2108008180a9c0010101010101
010101010101023a801871382d40582c
45003d624200001e011d007251d01e20
6e2855003d624200001e000000fc0053
4f4e5920545620202a30360a000000fd
003a3e0e460f000a2020202020200156
020343f05010050420223c3e03070206
015d5e5f62260d0707150750830f0000
77030c003000b83c2fd0890102030401
40000f1040506046e200fbe305df01e3
0e61668c0ad08a20e02d10103e96003d
6242000018011d8018711c1620582c25
003d624200009e000000000000000000
000000000000000000000000000000fb
BorderDimensions: 4
supported: 4
Border: 0 0 0 0
range: (0, 65535)
SignalFormat: TMDS
supported: TMDS
ConnectorType: HDMI
ConnectorNumber: 4
_ConnectorLocation: 4
1920x1080 (0x169) 148.500MHz +HSync +VSync *current +preferred
h: width 1920 start 2008 end 2052 total 2200 skew 0 clock 67.50KHz
v: height 1080 start 1084 end 1089 total 1125 clock 60.00Hz
4096x2160 (0x16a) 593.410MHz +HSync +VSync
h: width 4096 start 4184 end 4272 total 4400 skew 0 clock 134.87KHz
v: height 2160 start 2168 end 2178 total 2250 clock 59.94Hz
4096x2160 (0x16b) 297.000MHz +HSync +VSync
h: width 4096 start 5116 end 5204 total 5500 skew 0 clock 54.00KHz
v: height 2160 start 2168 end 2178 total 2250 clock 24.00Hz
4096x2160 (0x16c) 296.750MHz +HSync +VSync
h: width 4096 start 5116 end 5204 total 5500 skew 0 clock 53.95KHz
v: height 2160 start 2168 end 2178 total 2250 clock 23.98Hz
3840x2160 (0x16d) 593.410MHz +HSync +VSync
h: width 3840 start 4016 end 4104 total 4400 skew 0 clock 134.87KHz
v: height 2160 start 2168 end 2178 total 2250 clock 59.94Hz
3840x2160 (0x16e) 296.700MHz +HSync +VSync
h: width 3840 start 4016 end 4104 total 4400 skew 0 clock 67.43KHz
v: height 2160 start 2168 end 2178 total 2250 clock 29.97Hz

[eyeinsky]

I can confirm the same issue with an ASUS' GTX 960.

The official nvidia driver (ver 346.47, released 24th Feb) gives a blank screen on my tv when using HDMI and setting resolution to 3840x2160. When I start xfce4 the screen just goes blank and after a while says "no signal".

I'm currently using some nouveau version (the open source NVIDIA driver), but it doesn't support the card I have. It says "unknown model" or some such at boot time. I can still use the TV in full hd though, by using the DVI out of the videocard with a converter to HDMI (the connection itself will still be DVI AFAIK).

I've yet to try a manual compilation of the latest nouveau version -- the one I tried came through apt and was version 1:1.0.11-1.