On 12/01/2017 07:30 AM, Mark Brown wrote:
On Wed, Nov 29, 2017 at 03:32:51PM -0600, Andrew F. Davis wrote:
Leaving microphone bias off is a valid setting and even used in the DT binding document example. Add this setting here and document the same.
- ai31xx-micbias-vg - MicBias Voltage setting
0 or MICBIAS_OFF - MICBIAS output is powered off 1 or MICBIAS_2_0V - MICBIAS output is powered to 2.0V 2 or MICBIAS_2_5V - MICBIAS output is powered to 2.5V 3 or MICBIAS_AVDD - MICBIAS output is connected to AVDDThis doesn't make much sense. If we enable the microphone with a voltage of 0V that's not going to work terribly well - I'd expect this property to control the voltage set when it's enabled, not if it's enabled.
I agree about this not making much sense, but I'm not sure the right way forward here.
Personally I wouldn't have put MicBias voltage in DT to begin with, it is runtime configurable and depends on user runtime inserted microphone, not really a hardware description :/
The enable/disable is controlled by a DAPM and should be wired to enable whenever we are recording from the related microphone pin. So then without MICBIAS_OFF the user is forced to select from the above voltages whenever recording, which may not be correct if they are using a mic that doesn't need bias.
The best option I think would be to drop this from DT, but I don't feel like fighting that battle right now.