linux-kernel - RE: [alsa-devel] [PATCH] ASoC: eve: implement set_bias

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Date:   Fri, 25 Oct 2019 16:14:46 +0000
From:   "Lu, Brent" <brent.lu@...el.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>
CC:     "Rojewski, Cezary" <cezary.rojewski@...el.com>,
        Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
        Jie Yang <yang.jie@...ux.intel.com>,
        "Mark Brown" <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        "Subhransu S . Prusty" <subhransu.s.prusty@...el.com>,
        Richard Fontana <rfontana@...hat.com>,
        Tzung-Bi Shih <tzungbi@...gle.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "M, Naveen" <naveen.m@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [alsa-devel] [PATCH] ASoC: eve: implement set_bias_level
 function for rt5514

> 
> Can you clarify if the rt5514 needs the MCLK while it's doing the hotword
> detection?

No, running the detection does not raise the bias level so the set_bias_level 
will not be called. The mclk is only turned on then off in mixer control's handler 
(rt5514_dsp_voice_wake_up_put) when enabling the hotword detection.

> 
> My point is really that this patch uses a card-level BIAS indication, and I'd like
> to make sure this does not interfere with the audio DSP being in D3 state.

The function checks the name of dapm so it would only react when rt5514's 
bias level is changing. And also the idle_bias_off of the codec driver is true so 
it's target_bias_level should not be overwritten in the dapm_power_widgets() 
function. The behavior should be similar to the previous patch which is using 
supply widget.

Regards,
Brent