On Tue, May 10, 2016 at 11:18:03AM +0800, John Hsu wrote: > On 5/10/2016 12:35 AM, Mark Brown wrote: > > Well, the machine driver has to cope anyway. What's not clear to me is > > if the device *has* to use the internal clock when doing accessory > > detection or if it's just lower power. > If the codec only does accessory insertion detection, the driver can setup > it and doesn't need any clock. That can make lower power. But if the codec > wants to do advanced jack detection like mic or impedance, the driver needs > the internal clock to setup auto detection. Thus, when no headset connected > yet, we use the solution without internal clock for power saving. When we > want to do advanced detection, we use the solution with internal clock. I'm afraid this still leaves me none the wiser, sorry. If this switching to the internal clock is essential to the device operation then I'd expect it to be made transparent to callers so it should happen transparently rather than appearing via set_sysclk(). If it's not and it's just a performance optimisation then erroring out is definitely excessive but if the optimisation can be implemented transparently then it might be nice to do that.
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