我有一台联想 ThinkPad t470p，配有联想 ThinkPad Ultra Dock 170W 40A20170EU 扩展坞。此扩展坞有 2 个 DisplayPort 1.2。我通过 DisplayPort 连接了两台 4k 显示器 (LG 27UK850-W)。
Ubuntu 18.10 可以识别这两个显示器，但不允许启用两个分辨率为 3840x2160 的 4k 显示器（但它允许一个显示器为 3840x2160，另一个显示器为 1600x900）。
然而在 Windows 10 上可以运行，所以我相信这是软件限制。您能告诉我应该怎么做才能提供更多信息或解决问题吗？
编辑：删除了有关“硬件限制”的信息，这是因为两个显示器的比例不同（100％和200％）。
xrandr 输出：
Screen 0: minimum 320 x 200, current 6400 x 2160, maximum 8192 x 8192
eDP-1 connected primary 2560x1440+0+0 (normal left inverted right x axis y axis) 309mm x 174mm
2560x1440 60.05*+ 59.99 59.99 59.96 59.95
1920x1440 60.00
1856x1392 60.01
1792x1344 60.01
2048x1152 59.99 59.98 59.90 59.91
1920x1200 59.88 59.95
1920x1080 60.01 59.97 59.96 59.93
1600x1200 60.00
1680x1050 59.95 59.88
1600x1024 60.17
1400x1050 59.98
1600x900 59.99 59.94 59.95 59.82
1280x1024 60.02
1440x900 59.89
1400x900 59.96 59.88
1280x960 60.00
1440x810 60.00 59.97
1368x768 59.88 59.85
1360x768 59.80 59.96
1280x800 59.99 59.97 59.81 59.91
1152x864 60.00
1280x720 60.00 59.99 59.86 59.74
1024x768 60.04 60.00
960x720 60.00
928x696 60.05
896x672 60.01
1024x576 59.95 59.96 59.90 59.82
960x600 59.93 60.00
960x540 59.96 59.99 59.63 59.82
800x600 60.00 60.32 56.25
840x525 60.01 59.88
864x486 59.92 59.57
800x512 60.17
700x525 59.98
800x450 59.95 59.82
640x512 60.02
720x450 59.89
700x450 59.96 59.88
640x480 60.00 59.94
720x405 59.51 58.99
684x384 59.88 59.85
680x384 59.80 59.96
640x400 59.88 59.98
576x432 60.06
640x360 59.86 59.83 59.84 59.32
512x384 60.00
512x288 60.00 59.92
480x270 59.63 59.82
400x300 60.32 56.34
432x243 59.92 59.57
320x240 60.05
360x202 59.51 59.13
320x180 59.84 59.32
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-2 disconnected (normal left inverted right x axis y axis)
DP-3 disconnected (normal left inverted right x axis y axis)
HDMI-3 disconnected (normal left inverted right x axis y axis)
DP-3-1 connected 3840x2160+2560+0 (normal left inverted right x axis y axis) 600mm x 340mm
3840x2160 60.00*+ 30.00
2560x1440 59.95
1920x1080 60.00 60.00 59.94
1600x900 60.00
1280x1024 60.02
1280x800 59.81
1152x864 59.97
1280x720 60.00 60.00 59.94
1024x768 60.00
800x600 60.32
720x480 60.00 59.94
640x480 60.00 59.94 59.94
DP-3-2 connected (normal left inverted right x axis y axis)
3840x2160 60.00 + 30.00
2560x1440 59.95
1920x1080 60.00 60.00 59.94
1600x900 60.00
1280x1024 60.02
1280x800 59.81
1152x864 59.97
1280x720 60.00 60.00 59.94
1024x768 60.00
800x600 60.32
720x480 60.00 59.94
640x480 60.00 59.94 59.94
DP-3-3 disconnected (normal left inverted right x axis y axis)
驱动程序信息：（输出lshw -c video）
*-display
description: 3D controller
product: GM108M [GeForce 940MX]
vendor: NVIDIA Corporation
physical id: 0
bus info: pci@0000:02:00.0
version: a2
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress bus_master cap_list
configuration: driver=nvidia latency=0
resources: irq:142 memory:f3000000-f3ffffff memory:e0000000-efffffff memory:f0000000-f1ffffff ioport:d000(size=128)
*-display
description: VGA compatible controller
product: Intel Corporation
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
version: 04
width: 64 bits
clock: 33MHz
capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
configuration: driver=i915 latency=0
resources: irq:140 memory:f2000000-f2ffffff memory:c0000000-dfffffff ioport:e000(size=64) memory:c0000-dffff
CPU 信息：（输出cat /proc/cpuinfo）
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 158
model name : Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz
stepping : 9
microcode : 0x8e
cpu MHz : 1763.195
cache size : 6144 KB
physical id : 0
siblings : 8
core id : 0
cpu cores : 4
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 22
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp flush_l1d
bugs : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf
bogomips : 5616.00
clflush size : 64
cache_alignment : 64
address sizes : 39 bits physical, 48 bits virtual
power management:
(7 other cores skipped for brevity)
是的，我安装了额外的驱动程序 Nvidia 官方网站适用于我的显卡（940MX 和 Linux 64 位）