Linux Kernel GPU Clock Reparenting Vulnerability in H616 During Frequency Changes

A vulnerability in the Linux kernel's handling of GPU clock frequencies for the H616 chipset has been addressed. The issue arose because the H616 manual does not indicate that the GPU Phase-Locked Loop (PLL) can dynamically adjust frequencies. As a result, attempts to implement Dynamic Voltage and Frequency Scaling (DVFS) on the GPU caused errors and hangs in the Panfrost driver. The vulnerability was resolved by reparenting the GPU clock to the GPU1 clock during frequency changes, using an algorithm described in the manual and already supported by the CPU PLL notifier code.

Impact

The vulnerability could lead to improper handling of GPU frequencies, causing driver errors and GPU hangs.