Messages in this thread | | | Date | Thu, 20 Jan 2011 16:29:15 +0000 | From | Ben Dooks <> | Subject | Re: Locking in the clk API |
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On 11/01/11 03:15, Paul Mundt wrote: > On Tue, Jan 11, 2011 at 10:16:42AM +0800, Jeremy Kerr wrote: >> * clk_enable: may sleep >> >> * clk_disable: may not sleep, but it's possible to make the global >> clk_disable() atomic and defer the actual disable (clk->ops.disable()) to a >> non-atomic context. >> >> * clk_get_rate: may not sleep >> >> * clk_set_rate: may sleep >> >> As we build up our requirements, we can adjust as suitable. >> > This looks like a complete disaster, and is also completely inconsistent > with how the API is being used by the vast majority of users today. You > have an API that can or can not sleep with no indication as to which is > which based off of the API naming, which is just asking for trouble. > > As it is today, most users expect that these are all usable from atomic > context, and as far as I can tell the only special case you have are for > some crap busses with insane latencies. In this case you should simply > pile on _cansleep() versions of the API and make it apparent that those > drivers are the special cases, not the other way around.
The trouble is not with the drivers, is the fact there could be a clock tree where, say the closest to the driver is easy to control but the base of the tree may be a PLL which requires time to settle.
Now, there's a lot of work in the 'embedded' space where the focus is on the power consumption, so powering down PLLs when they are not needed is a good thing to have/
> Having half of the API sleepable and the other not with no indication of > which is which simply makes it completely unusable and error prone for > both atomic and non-atomic contexts.
I really don't like the fact that people are doing these things in atomic contexts, and I think we should apply some pressure to move the atomic caller cases to use systems where they can sleep such as using threaded-irq handlers (they work very nicely)
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