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#1 2021-11-25 03:39:17

napion
Member
Registered: 2015-04-11
Posts: 6

udevadm prints out constant changes to typec port0

I was trying to understand why plugging in a AC supply increases the laptop temperature. So I ran 'udevadm monitor -u' to see what rules are being fired. Interestingly I saw this output:

> udevadm monitor -u   
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing

UDEV  [348.291145] change   /devices/platform/USBC000:00/typec/port0 (typec)
UDEV  [348.609435] change   /devices/platform/USBC000:00/typec/port0 (typec)
UDEV  [350.339523] change   /devices/platform/USBC000:00/typec/port0 (typec)
UDEV  [350.456082] change   /devices/platform/USBC000:00/typec/port0 (typec)
UDEV  [351.276070] change   /devices/platform/USBC000:00/typec/port0 (typec)
UDEV  [351.582771] change   /devices/platform/USBC000:00/typec/port0 (typec)
UDEV  [351.789541] change   /devices/platform/USBC000:00/typec/port0 (typec)
UDEV  [352.189421] change   /devices/platform/USBC000:00/typec/port0 (typec)
UDEV  [352.389409] change   /devices/platform/USBC000:00/typec/port0 (typec)
UDEV  [352.696088] change   /devices/platform/USBC000:00/typec/port0 (typec)
UDEV  [352.902656] change   /devices/platform/USBC000:00/typec/port0 (typec)
UDEV  [353.209405] change   /devices/platform/USBC000:00/typec/port0 (typec)

There are about 3-4 events/sec related to some typec port0 changes. This laptop (ASUS GU502LV) has a single usb-c port and nothing is connected to this. Is this normal?

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#2 2021-11-25 16:45:50

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 18,082

Re: udevadm prints out constant changes to typec port0

My guess is that it is permitting the USB-C ports to allow USB devices to negotiate for more power when the system is on shore power.   Do those messages continue?

Other things that could be going on -- Your processor and perhaps GPU may have transitioned from a low power state to a higher performance state.
Also, your power supply will certainly be working a bit harder as it is not only powering the computer (which is ramping up its demand), it is also going to be charging the battery at a fairly high rate.
Finally, batteries get warm when they are charged as the charging efficiency is < 1.


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Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
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#3 2021-12-12 03:48:54

napion
Member
Registered: 2015-04-11
Posts: 6

Re: udevadm prints out constant changes to typec port0

Do these messages continue?

Yes, about 3 events/sec. I've also noticed that this happens even when not connected to a power source.

Your processor and perhaps GPU may have transitioned from a low power state to a higher performance state

You are right, something is happening with the GPU. I missed the relevant events because of the flood of messages from usb-c. When the power supply is connected, these are the events:

UDEV  [1130.982555] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:20/PNP0C09:01/PNP0C0A:03/power_supply/BAT0 (power_supply)
UDEV  [1131.086903] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:20/PNP0C09:01/PNP0C0A:03/power_supply/BAT0 (power_supply)
UDEV  [1133.956517] remove   /devices/pci0000:00/0000:00:1d.6/0000:3c:00.0/wakeup/wakeup59 (wakeup)
UDEV  [1134.261055] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:20/PNP0C09:01/ACPI0003:00/power_supply/AC0 (power_supply)
UDEV  [1134.321549] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:20/PNP0C09:01/ACPI0003:00/power_supply/AC0 (power_supply)

and when it is plugged out:

UDEV  [1294.329131] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:20/PNP0C09:01/PNP0C0A:03/power_supply/BAT0 (power_supply)
UDEV  [1294.514345] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:20/PNP0C09:01/ACPI0003:00/power_supply/AC0 (power_supply)
UDEV  [1294.560940] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:20/PNP0C09:01/PNP0C0A:03/power_supply/BAT0 (power_supply)
UDEV  [1294.717770] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:20/PNP0C09:01/ACPI0003:00/power_supply/AC0 (power_supply)
UDEV  [1304.427565] add      /devices/pci0000:00/0000:00:1d.6/0000:3c:00.0/wakeup/wakeup59 (wakeup)

I don't need the GPU on linux and I thought I had disabled it with these udev rules from Nvidia's docs:

❮ cat /etc/udev/rules.d/80-nvidia-pm.rules
SUBSYSTEM=="pci", ATTR{vendor}=="0x10de", ATTR{class}=="0x030000", TEST=="power/control", ATTR{power/control}="auto"
SUBSYSTEM=="pci", ATTR{vendor}=="0x10de", ATTR{class}=="0x030200", TEST=="power/control", ATTR{power/control}="auto"

Is the GPU being enabled when I plug the power supply in? If so how can I disable that behaviour? Are the udev events from usb-c innocuous enough that I can ignore them?

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