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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
