无法在外接显示器上启用 4K 分辨率

Question

我有一台笔记本电脑 - Toshiba Satellite L640-1157U i3-380M - 带有 HDMI 端口，可能支持 4K@30HZ。

我还有一个外接显示器，肯定支持4K@30HZ（win10环境下表现不错）。

该笔记本电脑安装了 manjaro 21.3.7，其 HDMI-0 的默认分辨率为 1920x1080。

xrandr                                                                                         ✔ 
Screen 0: minimum 320 x 200, current 3286 x 1080, maximum 8192 x 8192
LVDS connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 309mm x 174mm
   1366x768      60.00*+
   1280x720      59.97  
   1152x768      59.95  
   1024x768      59.95  
   800x600       59.96  
   848x480       59.94  
   720x480       59.94  
   640x480       59.94  
HDMI-0 connected 1920x1080+1366+0 (normal left inverted right x axis y axis) 1096mm x 616mm
   1920x1080     60.00*+  59.94    30.00    24.00    29.97    23.98  
   1920x1080i    60.00    50.00    59.94  
   1280x1024     60.02  
   1440x900      59.90  
   1280x960      60.00  
   1366x768      59.79  
   1280x800      59.91  
   1280x720      60.00    50.00    59.94  
   1024x768      60.00  
   800x600       60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   720x480i      60.00    59.94  
   640x480       60.00    59.94  
   720x400       70.08  
VGA-0 disconnected (normal left inverted right x axis y axis)
  3840x2160_30.00 (0x70e) 338.750MHz -HSync +VSync
        h: width  3840 start 4080 end 4488 total 5136 skew    0 clock  65.96KHz
        v: height 2160 start 2163 end 2168 total 2200           clock  29.98Hz

所以我输入以下命令来获取 3840x2160@30HZ。

cvt 3840 2160 30                                                                              
# 3840x2160 29.98 Hz (CVT) hsync: 65.96 kHz; pclk: 338.75 MHz
Modeline "3840x2160_30.00"  338.75  3840 4080 4488 5136  2160 2163 2168 2200 -hsync +vsync
xrandr --newmode "3840x2160_30.00"  338.75  3840 4080 4488 5136  2160 2163 2168 2200 -hsync +vsync
xrandr --addmode HDMI-0 3840x2160_30.00                                                       
xrandr --output HDMI-0 --mode 3840x2160_30.00

不幸的是，外接显示器只是一片空白（没有信号）。

xrandr                                                                                    
Screen 0: minimum 320 x 200, current 5206 x 2160, maximum 8192 x 8192
LVDS connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 309mm x 174mm
   1366x768      60.00*+
   1280x720      59.97  
   1152x768      59.95  
   1024x768      59.95  
   800x600       59.96  
   848x480       59.94  
   720x480       59.94  
   640x480       59.94  
HDMI-0 connected 3840x2160+1366+0 (normal left inverted right x axis y axis) 1096mm x 616mm
   1920x1080     60.00 +  59.94    30.00    24.00    29.97    23.98  
   1920x1080i    60.00    50.00    59.94  
   1280x1024     60.02  
   1440x900      59.90  
   1280x960      60.00  
   1366x768      59.79  
   1280x800      59.91  
   1280x720      60.00    50.00    59.94  
   1024x768      60.00  
   800x600       60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   720x480i      60.00    59.94  
   640x480       60.00    59.94  
   720x400       70.08  
   3840x2160_30.00  29.98* 
VGA-0 disconnected (normal left inverted right x axis y axis)

我还能做什么？