Am Dienstag, 14. Februar 2017, 13:01:14 CET schrieb Douglas Anderson: > The PMU Cortex M0 on rk3399 is intended to be used for things like > DDRFreq transitions, suspend/resume, and other things that are the > purview of ARM Trusted Firmware and not the kernel. As such, the > kernel shouldn't be messing with the clocks. Add CLK_IGNORE_UNUSED to > these clocks. > > Without this change, the following was observed on a Chromebook with a > rk3399 (using not-yet-upstream ARM Trusted Firmware code and > not-yet-upstream kernel code based on kernel-4.4): > > 1. We init the clock framework. > > 2. We start up "DDRFreq", which causes ATF to occasionally fire up the > M0 for transitions. Each time ATF fires up the M0 it will turn on > these clocks and each time it is done it will turn them off. > > 3. We finally get to the the part of the kernel that calls > clk_disable_unused() and we disables the clocks. > > You can see the race above. Basically everything is fine as long as > ARM Trusted Firmware isn't starting up the M0 at exactly the same time > that the kernel is disabling unused clocks. ...but if the race > happens then we go boom. > > Signed-off-by: Douglas Anderson <dianders at chromium.org> applied for 4.12 Thanks Heiko
