linux-kernel - Re: [PATCH v3] ASoC: fsl: imx-wm8962: Grant hw

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Date:	Wed, 18 Dec 2013 13:13:36 +0800
From:	Nicolin Chen <Guangyu.Chen@...escale.com>
To:	Mark Brown <broonie@...nel.org>
CC:	<lgirdwood@...il.com>, <alsa-devel@...a-project.org>,
	<tiwai@...e.de>, <perex@...ex.cz>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] ASoC: fsl: imx-wm8962: Grant hw_params/free()
 permission to control FLL

On Tue, Dec 17, 2013 at 10:50:02PM +0000, Mark Brown wrote:
> On Thu, Dec 12, 2013 at 05:59:28PM +0800, Nicolin Chen wrote:
> 
> > +	mask = WM8962_MIXINL_TO_HPMIXL_MASK | WM8962_MIXINR_TO_HPMIXL_MASK |
> > +		WM8962_IN4L_TO_HPMIXL_MASK | WM8962_IN4R_TO_HPMIXL_MASK;
> > +	bypass |= snd_soc_read(codec, WM8962_HEADPHONE_MIXER_1) & mask;
> > +	bypass |= snd_soc_read(codec, WM8962_HEADPHONE_MIXER_2) & mask;
> > +	bypass |= snd_soc_read(codec, WM8962_SPEAKER_MIXER_1) & mask;
> > +	bypass |= snd_soc_read(codec, WM8962_SPEAKER_MIXER_2) & mask;
> > +
> > +	/* Don't diable FLL if running multi-substreams or analogue bypass */
> > +	if (codec_dai->active != 1 || bypass)
> > +		return 0;
> 
> I don't think this works with the power down delay we do on playback -
> the DAI will go inactive when closed but we'll still have the CODEC
> active and using its clocks until the power down time has elapsed if
> it's a playback DAI.  Trying to reclock the device while active is at
> best risky, even if it's muted.
>
> I do think refcounting from both here and the bias level changes is
> going to be the most robust thing, that'd also avoid the need to peer
> into the CODEC register map.

I've tried count reference way to handle FLL enabler/disabler here before
I sent this version. But the result shows the FLL would be never disabled
in hw_free() because the refcount is accumulated to 2, one from hw_params()
and the other from set_bias_level(PREPARE), which just made this patch
meaningless to me.

So the reclocking with bypass checking seems to be the last resort I can
figure out right here as the playback flow for 'aplay -Dhw:0 44k16bit.wav
48k24bit.wav' does need to reprogram the FLL during CODEC active.

Thank you,
Nicolin Chen

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