Fixing Clock Tree Propagation in the Common Clk Framework

Explore critical issues in Linux's Common Clock Framework (CCF) during this 24-minute conference talk from the Linux Plumbers Conference. Examine how the CCF fails to maintain clock rate stability when CLK_SET_RATE_PARENT is involved, leading to unexpected rate changes across the clock tree. Learn about the fundamental problem where child clocks can modify parent rates without considering sibling clocks, resulting in incompatible rates and unexpected changes to related clocks. Discover the complications that arise in gate and mux scenarios, and understand why proposed fixes cannot be merged without breaking existing board implementations. Review real-world bug reports and recently-posted kunit tests that demonstrate these longstanding issues. Gain insights into potential solutions and strategies for maintaining backward compatibility with older boards that depend on the current behavior, while addressing the underlying clock tree propagation problems that have affected Linux kernel development for years.