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.
Cheers,
Peter.