On Thu, Nov 15, 2018 at 01:55:06AM +0200, Dimitris Papavasiliou wrote: > On 11/15/2018 01:02 AM, Mark Brown wrote: > > I've no idea what you're proposing, sorry. > I mentioned it in the message you replied to initially, so you > can consult that for more details if you want, but I'll give a > summary below: That was rather a long mail and I got a bit lost about what the proposal was. > As far as I could determine experimentally, switching clocks when > the DAC is not suspended seems to result in a spike at the input > of the DAC, the level of which doesn't depend on the digital > volume setting (so that it's always very loud). I tried various This is fairly normal; the DAC is partly digital. > Avoiding the spike instead of relying on muting seems preferable, > but, since the power state of the PCM5122 is manipulated by the > CODEC driver, in response to requests to set the bias level, I'm > concerned about potential race conditions. Given that there's no substantial delays in the power up/down paths of the driver you probably want to set idle_bias_off and possibly also configuring ignore_pmdown_time to force immediate poweroff. That should get the device powered down rapidly, though bouncing the power on and off all the time isn't great. If you do need ignore_pmdown_time then it's probably better to add a higher level interface that allows the machine driver to cancel all power down timers. > if (no_switch_needed) > return; > > snd_soc_dapm_mutex_lock(dapm); > force = (snd_soc_dapm_get_bias_level(dapm) != SND_SOC_BIAS_OFF); > > if (force) > snd_soc_dapm_force_bias_level(dapm, SND_SOC_BIAS_OFF); > > /* Switch the clock here. */ > > ... > > if (force) > snd_soc_dapm_sync_unlocked(dapm); > > snd_soc_dapm_mutex_unlock(dapm); This is not a good idea, fiddling around with DAPM internals from drivers is going to be very fragile as things change in future.
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