linux-kernel - Re: [PATCH v4] ASoC: tas2552: Support TI TAS2552 Amplifier

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Message-ID: <20140703150621.GQ5814@saruman.home>
Date:	Thu, 3 Jul 2014 10:06:22 -0500
From:	Felipe Balbi <balbi@...com>
To:	Dan Murphy <dmurphy@...com>
CC:	<balbi@...com>, <linux-sound@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <alsa-devel@...a-project.org>,
	<broonie@...nel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4] ASoC: tas2552: Support TI TAS2552 Amplifier

Hi,

On Thu, Jul 03, 2014 at 09:57:39AM -0500, Dan Murphy wrote:
> On 07/03/2014 09:52 AM, Felipe Balbi wrote:
> > Hi,
> >
> > On Thu, Jul 03, 2014 at 09:39:53AM -0500, Dan Murphy wrote:
> >> +static int tas2552_set_dai_fmt(struct snd_soc_dai *dai, unsigned int fmt)
> >> +{
> >> +	u8 serial_format;
> >> +	struct snd_soc_codec *codec = dai->codec;
> >> +
> >> +	switch (fmt & SND_SOC_DAIFMT_MASTER_MASK) {
> >> +	case SND_SOC_DAIFMT_CBS_CFS:
> >> +		serial_format = 0x00;
> >> +		break;
> >> +	case SND_SOC_DAIFMT_CBS_CFM:
> >> +		serial_format = TAS2552_WORD_CLK_MASK;
> >> +		break;
> >> +	case SND_SOC_DAIFMT_CBM_CFS:
> >> +		serial_format = TAS2552_BIT_CLK_MASK;
> >> +		break;
> >> +	case SND_SOC_DAIFMT_CBM_CFM:
> >> +		serial_format = (TAS2552_BIT_CLK_MASK | TAS2552_WORD_CLK_MASK);
> >> +		break;
> >> +	default:
> >> +		return -EINVAL;
> >> +	}
> >> +
> >> +	pm_runtime_get_sync(codec->dev);
> >> +
> >> +	snd_soc_update_bits(codec, TAS2552_SER_CTRL_1,
> >> +			    (TAS2552_BIT_CLK_MASK | TAS2552_WORD_CLK_MASK),
> >> +			    serial_format);
> >> +
> >> +	pm_runtime_put(codec->dev);
> > I have a feeling it's better to just put at the end of the function.
> > Remember your pm_runtime_put() will issue i2c transfers which can take a
> > looooooong time ;-)
> 
> I thought about that but the next switch case could return if the format
> mask is invalid which means the runtime calls would not be balanced.
> 
> So I decided to wrap the snd_soc calls with the pm_runtime calls to keep it
> balanced.

it looks like you can do both switch statements outside of the
pm_runtime region and cache results on serial_format and do a single
write to CTRL_1 register (?). If not, then just use two local variables.

-- 
balbi

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