linux-kernel - Re: [PATCH v2] ASoC: fsl_esai: Add ESAI CPU DAI driver

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Date:	Fri, 10 Jan 2014 10:35:39 +0800
From:	Nicolin Chen <Guangyu.Chen@...escale.com>
To:	Mark Brown <broonie@...nel.org>
CC:	<timur@...i.org>, <alsa-devel@...a-project.org>,
	<robh+dt@...nel.org>, <pawel.moll@....com>, <mark.rutland@....com>,
	<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>,
	<rob@...dley.net>, <lgirdwood@...il.com>, <perex@...ex.cz>,
	<tiwai@...e.de>, <grant.likely@...aro.org>, <shawn.guo@...aro.org>,
	<devicetree@...r.kernel.org>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v2] ASoC: fsl_esai: Add ESAI CPU DAI driver

Resent this because of losing attached file.

On Fri, Jan 10, 2014 at 10:32:52AM +0800, Nicolin Chen wrote:
> On Thu, Jan 09, 2014 at 06:44:53PM +0000, Mark Brown wrote:
> > On Thu, Jan 09, 2014 at 06:57:58PM +0800, Nicolin Chen wrote:
> > 
> > > +/**
> > > + * This function configures the ratio between MCLK (HCK) and BCLK (SCK)
> > > + * (For DAI Master Mode only)
> > > + *
> > > + * Note: Machine driver should calculate the ratio to call this function.
> > > + * 	 Only effective after calling set_dai_sysclk() to set HCK direction.
> > > + */
> > > +static int fsl_esai_set_bclk_ratio(struct snd_soc_dai *dai, unsigned int ratio)
> > 
> > Why does the machine driver have to do this by hand, being able to
> > override is fine but having sensible defaults is easier?  Or does it
> > actually do that and the comment just needs updating?
> 
> The divider part of ESAI is pretty complicated due to caring about three
> configure bits - ETO, ETI, HCKD. (I've attached a diagram to this mail.)
> So setting sysclk() alone is not enough to take care all the configurations.
> That's why I designed these two interfaces at the first place. And it should
> be hard to find a default situation.
> 
> But there is one approach to omit this calling for machine driver is to do
> the set_bclk_ratio() at this CPU DAI driver. And this might be a good idea
> because we can then separate the settings between PLAYBACK and CAPTURE, even
> though we might then need to check the Master or Slave state to apply the
> settings accordingly.
> 
> I'll try this idea in v3 if you feel it's plausible.
> 
> > > +	ret = devm_snd_soc_register_component(&pdev->dev, &fsl_esai_component,
> > > +					      &fsl_esai_dai, 1);
> > > +	if (ret) {
> > > +		dev_err(&pdev->dev, "failed to register DAI: %d\n", ret);
> > > +		return ret;
> > > +	}
> > > +
> > > +	ret = imx_pcm_dma_init(pdev);
> > > +	if (ret)
> > > +		dev_err(&pdev->dev, "failed to init imx pcm dma: %d\n", ret);
> > > +
> > > +	/* Reset ESAI unit */
> > > +	regmap_write(esai_priv->regmap, REG_ESAI_ECR, ESAI_ECR_ERST);
> > > +
> > > +	/*
> > > +	 * We need to enable ESAI so as to access some of its registers.
> > > +	 * Otherwise, we would fail to dump regmap from user space.
> > > +	 */
> > > +	regmap_write(esai_priv->regmap, REG_ESAI_ECR, ESAI_ECR_ESAIEN);
> > 
> > I would expect to see the hardware initialisation before we start
> > registering with the core otherwise the core might start trying to run
> > prior to the hardware being initialised.
> 
> Will switch this initial code in v3 as your suggestion.
> 
> Thank you,
> Nicolin Chen

Download attachment "esai_div.jpg" of type "image/jpeg" (61359 bytes)