The string breaks down into three components:
In essence, “exynos usb device4000 hot” means the host PC detected an Exynos device in download mode (PID:4000), but the connection became unstable—often due to power delivery issues, cable problems, driver conflicts, or improper handshaking during firmware transfer. exynos usb device4000 hot
dmesg | grep -i "usb.*4000"
[ 1234.567890] exynos-usb 11200000.usb: PHY4-4000 temp=87C, threshold=85C
[ 1234.567901] usb 4-4000: device descriptor read/64, error -110
[ 1234.567912] thermal thermal_zone8: USB PHY critical trip point
User symptom: The error appears randomly, sometimes after 2 seconds, sometimes after 2 minutes.
Fix: The USB cable was running near a powerful switching power supply. Shielding and ferrite beads on the cable reduced EMI, and disabling autosuspend removed the final error. PHY power filtering and rails:
Despite the name, "USB Device4000" usually does not refer to a flash drive or peripheral you have plugged in. In the context of Samsung’s Exynos chipsets, this refers to the internal USB 3.0 Controller. Layout:
Essentially, this is the hardware component responsible for managing the charging port and data transfer. Even if nothing is plugged into the port, this controller remains active and monitored by the system’s thermal sensors.
User symptom: Heimdall detects the device in download mode, but after “Claiming interface,” the error appears.
Fix: Using Zadig, the user replaced the Samsung driver with libusbK (not WinUSB). Then they disabled Windows Fast Startup, which was causing USB port reinitialization issues on reboot.