On Wed, Nov 22, 2017 at 01:33:37PM +0100, Ricard Wanderlof wrote: Always CC maintainers on postings if you want them to be reliably seen... > I'm having an issue with a codec where the normal DAPM procedure of > disabling most of the codec when there is no stream ongoing results in > large clicks when a playback stream starts and stops, because the output > jumps from 0V when the output is disabled to over a volt when the output > is enabled. > There appears to be a 'slow stop/start' feature in the codec, however, it > takes about one second to ramp up and down the output voltage, and that is > too long a delay when starting a stream. The CODEC driver is broken, it shouldn't be powering off on idle if it takes a second to ramp, it should be leaving VMID up while the system is running - this is what the _STANDBY bias level is all about. Look at what older CODEC drivers like the wm8731 do. > Another use for this feature is that we have had a lot of problems over > the years with buggy I2S interfaces misbehaving when streams are started > and stopped, and there would be an advantage to letting the AIF run the > whole time after startup. This is why we've got the digital_mute() callback - the idea is that the output is just going to be discarded until the interface has had a chance to settle down.
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