On Wed, Sep 30, 2015 at 05:36:49AM -0700, Michael Turquette wrote: > Quoting Maxime Ripard (2015-08-28 20:55:57) > > Hi Mike, > > > > On Tue, Aug 25, 2015 at 02:50:51PM -0700, Michael Turquette wrote: > > > Quoting Maxime Ripard (2015-08-20 08:15:10) > > > > On Tue, Aug 18, 2015 at 09:43:56AM -0700, Michael Turquette wrote: > > > > > Quoting Maxime Ripard (2015-08-18 08:45:52) > > > > > > Hi Mike, > > > > > > > > > > > > On Fri, Aug 07, 2015 at 12:09:27PM -0700, Michael Turquette wrote: > > > > > > > All of the other kitchen sink stuff (DT binding, passing the flag > > > > > > > back > > > > > > > to the framework when the clock consumer driver calls clk_put) > > > > > > > was left > > > > > > > out because I do not see a real use case for it. If one can > > > > > > > demonstrate > > > > > > > a real use case (and not a hypothetical one) then this patch > > > > > > > series can > > > > > > > be expanded further. > > > > > > > > > > > > I think there is a very trivial use case for passing back the > > > > > > reference to the framework, if during the probed, we have something > > > > > > like: > > > > > > > > > > > > clk = clk_get() > > > > > > clk_prepare_enable(clk) > > > > > > foo_framework_register() > > > > > > > > > > > > if foo_framework_register fails, the sensible thing to do would be > > > > > > to > > > > > > call clk_disable_unprepare. If the clock was a critical clock, you > > > > > > just gated it. > > > > > > > > > > Hmm, a good point. Creating the "pass the reference back" call is not > > > > > hard technically. But how to keep from abusing it? E.g. I do not want > > > > > that call to become an alternative to correct use of clk_enable. > > > > > > > > > > Maybe I'll need a Coccinelle script or just some regular sed to > > > > > occasionally search for new users of this api and audit them? > > > > > > > > > > I was hoping to not add any new consumer api at all :-/ > > > > > > > > I don't think there's any abuse that can be done with the current API, > > > > nor do I think you need to have new functions either. > > > > > > > > If the clock is critical, when the customer calls > > > > clk_unprepare_disable on it, simply take back the reference you gave > > > > in the framework, and you're done. Or am I missing something? > > > > > > Maybe I am the one missing something? My goal was to allow the consumer > > > driver to gate the critical clock. So we need clk_disable_unused to > > > actually disable the clock for that to work. > > > > Yeah, but I guess the consumer driver clock gating is not the default > > mode of operations. > > > > Under normal circumstances, it should just always leave the clock > > enabled, all the time. > > > > > I think you are suggesting that clk_disable_unused should *not* disable > > > the clock if it is critical. Can you confirm that? > > > > By default, yes. > > > > Now, we also have the knowledgeable driver case wanting to force the > > clock gating. I think it's an orthogonal issue, we might have the same > > use case for non-critical clocks, and since it's hard to get that done > > with the current API, and that we don't really know what a > > knowledgeable driver will look like at this point, maybe we can just > > delay this entirely until we actually have one in front of us? > > Yes. I discussed this face to face with Lee last week at Linaro Connect. > I proposed the following: > > 1) support an always-on clk, which is enabled by the framework at > registration-time and can never be claimed and gated > > 2) support a hand-off clk, which is enabled by the framework at > registration-time and whose reference counts are handed off to the first > driver to get, prepare and enable this clk > > 3) forget about knowledgeable drivers because nobody needs this (yet) > > Lee was happy with this. Does it sound OK to you?
Yep, it sounds good! See you in Dublin, Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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