Re: [PATCH] clk: rockchip: Set "ignore unused" for PMU M0 clocks on rk3399
From: Heiko Stuebner
Date: Tue Feb 21 2017 - 12:47:55 EST
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@xxxxxxxxxxxx>
applied for 4.12