linux-kernel - Re: [PATCH v1 3/4] ASoC: Intel: bytcr_rt5651: use devm_clk_get

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Date:   Wed, 6 Oct 2021 19:50:45 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Mark Brown <broonie@...nel.org>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
        Jie Yang <yang.jie@...ux.intel.com>,
        Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
Subject: Re: [PATCH v1 3/4] ASoC: Intel: bytcr_rt5651: use
 devm_clk_get_optional() for mclk

On Wed, Oct 06, 2021 at 11:37:24AM -0500, Pierre-Louis Bossart wrote:
> On 10/6/21 11:23 AM, Andy Shevchenko wrote:
> > On Wed, Oct 06, 2021 at 10:51:52AM -0500, Pierre-Louis Bossart wrote:
> >> On 10/6/21 10:04 AM, Andy Shevchenko wrote:

...

> >>>  	if (SND_SOC_DAPM_EVENT_ON(event)) {
> >>> -		if (byt_rt5651_quirk & BYT_RT5651_MCLK_EN) {
> >>> -			ret = clk_prepare_enable(priv->mclk);
> >>> -			if (ret < 0) {
> >>> -				dev_err(card->dev,
> >>> -					"could not configure MCLK state");
> >>> -				return ret;
> >>> -			}
> >>> +		ret = clk_prepare_enable(priv->mclk);
> >>> +		if (ret < 0) {
> >>> +			dev_err(card->dev, "could not configure MCLK state");
> >>> +			return ret;
> >>>  		}
> >>
> >> I don't get why you removed the test on the BYT_RT5651_MCLK_EN quirk,
> >> see below it was designed as a fall-back mode. We don't want to return
> >> an error when we know the clock is not present/desired.
> > 
> > Why should we do a unneeded test? When we switch to the optional, there
> > will be no error from these CCF APIs. Besides that it drops indentation
> > level and makes code neat.
> 
> By looking at this code only one cannot really visualize that it's a
> no-op. I personally prefer to see explicit intent rather than have to
> dig hundreds of lines below what this clock is optional.
> 
> I am also not even sure that in real products this clock is actually
> optional,

The code tells that it's optional. If it's not the case, the code has
to be fixed accordingly.

> the default is to make use of it:
> 
> #define BYT_RT5651_DEFAULT_QUIRKS	(BYT_RT5651_MCLK_EN | \
> 
> and the only platform without this clock is "Minnowboard Max B3" -
> probably not used by anyone. I fried mine a long time ago.
> 
> We'd need to Hans to comment on this since he's really the only one
> maintaining this code.

Additional pair of eyes and a brain is always good to have!

...

> >> that part in the probe looks fine, but the changes above are controversial.
> > 
> > I didn't get. How controversial? Why? The whole point of _optional is to get
> > rid of unneeded checks (since they are _anyway_ be called).
> 
> It's inconsistent since you kept the following part but no longer use it:

It's used in some cases, but not with CLK APIs where it's redundant.

Otherwise I would remove it completely (actually it's possible to replace
it with the !priv->mclk test.

> +		/*
> +		 * Fall back to bit clock usage when clock is not
> +		 * available likely due to missing dependencies.
> +		 */
> +		if (!priv->mclk)
> +			byt_rt5651_quirk &= ~BYT_RT5651_MCLK_EN;

-- 
With Best Regards,
Andy Shevchenko