USB-C adapter like Dell DA300 using > 5 W

[Paul Menzel]

Dear Linux folks,


On the Intel Kaby Lake laptop Dell XPS 13 9360 with Debian sid/unstable 
and *powertop* 2.15-3, connecting a USB-C adapter like Dell DA300 or LMP 
USB-C mini Dock (P/N 15954) [1] and connecting only an Ethernet cable 
(module r8152 is used), the adapter gets very hot, and according to 
PowerTOP it uses over 5 Watts – almost more as the laptop idling.

    $ lsusb
    Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    Bus 001 Device 002: ID 0cf3:e300 Qualcomm Atheros Communications 
QCA61x4 Bluetooth 4.0
    Bus 001 Device 003: ID 04f3:2234 Elan Microelectronics Corp. 
Touchscreen
    Bus 001 Device 004: ID 0c45:670c Microdia Integrated Webcam HD
    Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
    Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    Bus 003 Device 002: ID 2109:2820 VIA Labs, Inc. VL820 Hub
    Bus 003 Device 003: ID 06c4:c412 Bizlink International Corp. DELL DA300
    Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
    Bus 004 Device 002: ID 2109:0820 VIA Labs, Inc. VL820 Hub
    Bus 004 Device 003: ID 0bda:8153 Realtek Semiconductor Corp. 
RTL8153 Gigabit Ethernet Adapter

With `LANG= sudo powertop --auto-tune` it stays high.

PowerTOP:

```
The battery reports a discharge rate of 6.01 W
The energy consumed was 146 J
The estimated remaining time is 3 hours, 51 minutes

Summary: 384.6 wakeups/second,  0.0 GPU ops/seconds, 0.0 VFS ops/sec and 
8.5% CPU use

Power est.              Usage       Events/s    Category       Description
  5.94 W      0.0%                      Device         Display backlight
  5.23 W    100.0%                      Device         USB device: USB 
Optical Mouse (Logitech)
  4.62 W     66.1%                      Device         USB device: USB 
10/100/1000 LAN (Realtek)
  205 mW    100.0%                      Device         USB device: 
Fujitsu Keyboard (Fujitsu)
 14.1 mW     13.5 ms/s       0.9        kWork intel_atomic_commit_work
```

At another time:

```
The battery reports a discharge rate of 10.5 W
The energy consumed was 235 J
The estimated remaining time is 2 hours, 20 minutes

Summary: 395.8 wakeups/second,  0.0 GPU ops/seconds, 0.0 VFS ops/sec and 
23.8% CPU use

Power est.              Usage       Events/s    Category       Description
  7.13 W    100.0%                      Device         USB device: USB 
10/100/1000 LAN (Realtek)
  3.92 W     15.8%                      Device         Display backlight
  320 mW      0.0 us/s      0.00        Process        [PID 1349] 
/usr/bin/pipewire
 63.6 mW     65.4 ms/s       0.5        Process        [PID 4982] 
/usr/lib/thunderbird/thunderbird
 24.9 mW     25.6 ms/s       6.7        Process        [PID 37753] 
/usr/lib/firefox-nightly/firefox-bin -contentproc -isForBrowser 
-prefsLen 36793 -prefMapSize 265654 -jsInitLe
 14.7 mW     15.1 ms/s       0.5        kWork 
intel_atomic_commit_work
```

The heat of the USB-C adapter might suggest, that it draws that much 
power. What is your experience? Can you suggest something?


Kind regards,

Paul


[1]: 
https://lmp-adapter.com/product/lmp-usb-c-mini-dock/?attribute_pa_color=silver
     "LMP USB-C mini Dock (P/N 15954)"