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

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Message-ID: <20200915142743.GB9675@piout.net>
Date:   Tue, 15 Sep 2020 16:27:43 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Mark Brown <broonie@...nel.org>,
        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 16:14:01+0200, Miquel Raynal wrote:
> Mark Brown <broonie@...nel.org> wrote on Tue, 15 Sep 2020 15:10:25
> +0100:
> 
> > On Tue, Sep 15, 2020 at 03:02:07PM +0200, Alexandre Belloni wrote:
> > > 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.  
> > 
> > Is it increasing steady state power consumption or is it just drawing
> > more power during the ramp (ie, peak current consumption is bigger)?
> > Usually this is trading off clean ramps for fast ramps rather than
> > affecting steady state.  If it's affecting steady state a control seems
> > sensible.
> 
> Indeed, it is just affecting the ramp (peak current is bigger).
> 

However, forcing powerup at probe time versus at play time means that
you consume power even when not playing audio.

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