linux-kernel - Re: [alsa-devel][PATCH 1/3] SoC: fsl

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Message-ID: <20150121173619.GA1184@Asurada>
Date:	Wed, 21 Jan 2015 09:36:21 -0800
From:	Nicolin Chen <nicoleotsuka@...il.com>
To:	Zidan Wang <b50113@...escale.com>
Cc:	Zidan Wang <zidan.wang@...escale.com>, timur@...i.org,
	Xiubo.Lee@...il.com, lgirdwood@...il.com, broonie@...nel.org,
	perex@...ex.cz, tiwai@...e.de, alsa-devel@...a-project.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [alsa-devel][PATCH 1/3] SoC: fsl_sai: add sai master mode support

On Wed, Jan 21, 2015 at 05:25:32PM +0800, Zidan Wang wrote:
> On Tue, Jan 20, 2015 at 10:07:03PM -0800, Nicolin Chen wrote:
> > On Tue, Jan 20, 2015 at 08:21:18PM +0800, Zidan Wang wrote:

> > > +	if ((tx && sai->synchronous[TX]) || (!tx && !sai->synchronous[RX])) {
> > > +		regmap_update_bits(sai->regmap, FSL_SAI_RCR2,
> > > +			FSL_SAI_CR2_MSEL_MASK, FSL_SAI_CR2_MSEL(sai->mclk_id));

> > "tx && sai->synchronous[TX]" means the playback in synchronous
> > mode (TX following RX). What if the recording has been already
> > activated with an MSEL setting at this point? Then the playback
> > stream, as a secondary stream, will overwrite MSEL of the first
> > stream -- Record. Same would happen to the DIV configuration.
> > 
> When TX following RX(or RX following TX), TX and RX works on same bit
> clock and frame clock. They will use same MCLK source, and just need set
> the bclk DIV for RX(or TX). The secondary stream will overwrite MSEL and
> bclk DIV of the first stream, but it doesn't matter.
> 
> For RX(or TX) sync:
> fsl_sai_dai.symmetric_rates = 1;
> fsl_sai_dai.symmetric_channels = 1;
> fsl_sai_dai.symmetric_samplebits = 1;

Ah, I forgot we have protection here. It's fine then.

> When TX and RX both works on async mode, TX and RX may works on
> different bit clock and frame clock. We need set MCLK source and bclk
> DIV for TX and RX. mclk_id just save a MCLK source id, so i need to define
> mclk_id[2] for differnet stream.

Yes, you need to change this part as you just realized.

And one more thing for your coding style for multi-line comment:
/*
 * Typically use this format.
 */

Thanks
Nicolin
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