linux-kernel - Re: [PATCH 3/3] ASoC: tlv320aic32x4: Enable fast charge

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Date:   Tue, 15 Sep 2020 15:02:07 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 3/3] ASoC: tlv320aic32x4: Enable fast charge

On 15/09/2020 12:50:34+0100, Mark Brown wrote:
> On Tue, Sep 15, 2020 at 10:26:02AM +0200, Alexandre Belloni wrote:
> > On 11/09/2020 19:31:40+0200, Miquel Raynal wrote:
> 
> > > +	/*
> > > +	 * Enable the fast charging feature and ensure the needed 40ms ellapsed
> > > +	 * before using the analog circuits.
> > > +	 */
> > > +	snd_soc_component_write(component, AIC32X4_REFPOWERUP,
> > > +				AIC32X4_REFPOWERUP_40MS);
> > > +	msleep(40);
> > > +
> 
> > Maybe the actual REFPOWERUP value could be exposed as a control so
> > userspace has a way to set the policy? 
> 
> We very rarely do this, there's not usially anything 
> 

Could you suggest something then? This mainly changes the power
codec power consumption. I guess people will want to trade latency
for less consumption.

> > I'm not sure it make sense to have the delay in probe because it is not
> > enable the analog part of the codec. The delay should probable be after
> > the clocks have been set up because the datasheet says that it is mdac
> > and madc that is starting the analog circuitry.
> 
> Deferring the delay to a workqueue is the usual thing where there's
> concerns about slowing down boot.

Well, that was not my concern. I didn't realize Miquel actually used the
Force power-up values and though the actual power up happened after
configuring the clocks (as is the case for the dafule values). In this
case, the delay is at the proper location.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com