On 03/12/2013 11:08 PM, Bill Huang wrote: > On Wed, 2013-03-13 at 12:42 +0800, Stephen Warren wrote: >> On 03/12/2013 07:47 PM, Bill Huang wrote: >>> On Tue, 2013-03-12 at 21:40 +0800, Russell King - ARM Linux wrote: >>>> On Tue, Mar 12, 2013 at 05:37:41AM -0700, Bill Huang wrote: >>>>> Add the below four notifier events so drivers which are interested in >>>>> knowing the clock status can act accordingly. This is extremely useful >>>>> in some of the DVFS (Dynamic Voltage Frequency Scaling) design. >>>>> >>>>> PRE_CLK_ENABLE >>>>> POST_CLK_ENABLE >>>>> PRE_CLK_DISABLE >>>>> POST_CLK_DISABLE >>>>> >>>>> Signed-off-by: Bill Huang <bilhu...@nvidia.com> >>>> >>>> NAK. *Sigh* NO, this is the wrong level to be doing stuff like this. >>>> >>>> The *ONLY* thing that clk_prepare_enable() and clk_prepare_disable() should >>>> *EVER* be doing is calling clk_prepare(), clk_enable(), clk_disable() and >>>> clk_unprepare(). Those two functions are *merely* helpers for drivers >>>> who don't wish to make the individual calls. >>>> >>>> Drivers are still completely free to call the individual functions, at >>>> which point your proposal breaks horribly - and they _do_ call the >>>> individual functions. >>> >>> I'm proposing to give device driver a choice when it knows that some >>> driver might be interested in knowing its clock's enabled/disabled state >>> change at runtime, this is very important for centralized DVFS core >>> driver. It is not meant to be covering all cases especially for drivers >>> which is not part of the DVFS, so we don't care if it is calling >>> clk_enable/disable directly or not. >> >> I believe the point Russell is making is not that the idea behind this >> patch is wrong, but simply that the function where you put the hooks is >> wrong. The hooks should at least be in clk_enable/clk_disable and not >> clk_prepare_enable/clk_disable_unprepare, since any driver is free to >> call clk_prepare separately from clk_enable. The hooks should be >> implemented in the lowest-level common function that all >> driver-accessible paths call through. > > Thanks, I know the point, but unfortunately there is no good choice for > hooking this since those low level functions clk_enable/clk_disable will > be called in interrupt context so it is not possible to send notify. We > might need to come out a better approach if we can think of any. > Currently I still think this is acceptable (Having all the drivers which > are using our interested clocks call these function to enable/disable > clock in their runtime_pm calls) though it's not perfect.
No, that definitely won't work. Not all drivers use those APIs, nor should they. _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
