Messages in this thread | | | Subject | Re: [PATCH] clk: clk_register: Correctly initialize enable_count | From | Rhyland Klein <> | Date | Wed, 10 Feb 2016 13:34:16 -0500 |
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On 2/9/2016 9:56 PM, Emilio López wrote: > Hi, > > El 09/02/16 a las 19:48, Rhyland Klein escribió: >> When clocks are registered, they could be enabled already in >> hardware. As of now, the enable count will start at 0. When this >> happens, it means a clock is enabled and the framework doesn't know >> that, so it will always report it as disabled. > > Keep in mind that during the boot process, towards the end, unused > clocks get disabled, so the state remains in sync. If suddenly the > enable_count on unused clocks is not 0, this will break and unused > clocks will remain on, wasting power.
Hmm, I had misread the logic in clk_disable_unused_subtree(), namely I inverted the check on enable_count when I was looking at it. It does seem like it would take care of the clocks I was referring to.
> > http://lxr.free-electrons.com/source/drivers/clk/clk.c#L244 > > What issue were you having that prompted you to write this patch?
I ran into the situation where a peripheral clock was enabled before the kernel loaded, and I was trying to disable it in the clk-tegra210 driver. Calling clk_disable() won't work, as the clock doesn't have an enable_count.
I do think that the clk_disable_unused_subtree() should pick up the slack, but I was trying to disable it before the cleanup code to remove unused clocks ran.
I think you are right and the clean up code should cover the situation I was looking at.
Thanks. -rhyland
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