On 03/14/2013 07:20 PM, Bill Huang wrote: > On Fri, 2013-03-15 at 01:54 +0800, Stephen Warren wrote: >> On 03/14/2013 03:28 AM, Bill Huang wrote: >>> On Thu, 2013-03-14 at 17:21 +0800, Peter De Schrijver wrote: >>>> On Thu, Mar 14, 2013 at 03:15:11AM +0100, Bill Huang wrote: >>>> >>>>> I don't think deferring will work either, considering the usage of DVFS, >>>>> device voltage is tightly coupled with frequency, when clock rate is >>>>> about to increase, we have to boost voltage first and we can lower the >>>>> voltage after the clock rate has decreased. All the above sequence have >>>>> to be guaranteed or you might crash, so deferring not only make thing >>>>> complicated in controlling the order but also hurt performance. >>>> >>>> But we could use notifiers in clk_prepare/clk_unprepare to set the voltage >>>> no? >>>> As clk_prepare/clk_unprepare have to be called before clk_enable or after >>>> clk_disable, the voltage can be raised to a safe level, before the clock >>>> becomes active. >>> >>> Thanks Peter, actually I'm just about to propose my v2 RFC which add >>> notifier in clk_prepare/clk_unprepare. >> >> Can't clk_set_rate() be called while the clock is prepared, or even >> enabled? I don't see how your proposal would work. > > I think it works with just a little sacrifice on saving more power but > that's related minor. Taking clk_prepare as an indicator on that clock > will be enabled later, so we can raise the voltage to a safe level > (according to the current rate or maybe default rate when clk_prepare is > called, some time late when clk_set_rate() is called we can adjust again > according to the requested rate change)
Is clk_set_rate() only legal to call in non-atomic contexts then? The header file doesn't say, although I guess since many other functions explicitly say they can't, then by omission it can... _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev