[PATCH V3] ASoC: fsl_esai: fix channel swap issue when stream starts

[Nicolin Chen]

Hi Shengjiu,

Two more trivial comments inline.

On Tue, Feb 26, 2019 at 03:12:25AM +0000, S.j. Wang wrote:
> There is very low possibility ( < 0.1% ) that channel swap happened
> in beginning when multi output/input pin is enabled. The issue is
> that hardware can't send data to correct pin in the beginning with
> the normal enable flow.
> 
> This is hardware issue, but there is no errata, the workaround flow
> is that: Each time playback/recording, firstly clear the xSMA/xSMB,
> then enable TE/RE, then enable xSMB and xSMA (xSMB must be enabled
> before xSMA). Which is to use the xSMA as the trigger start register,
> previously the xCR_TE or xCR_RE is the bit for starting.
> 
> Fixes commit 43d24e76b698 ("ASoC: fsl_esai: Add ESAI CPU DAI driver")
> Cc: <stable at vger.kernel.org>
> Re> @@ -361,21 +363,13 @@ static int fsl_esai_set_dai_tdm_slot(struct snd_soc_dai *dai, u32 tx_mask,
>  	esai_priv->slot_width = slot_width;
>  	esai_priv->slots = slots;
> +	esai_priv->tx_mask    = tx_mask;
> +	esai_priv->rx_mask    = rx_mask;

Not necessary to have tabs before "="s.

> @@ -611,12 +606,23 @@ static int fsl_esai_trigger(struct snd_pcm_substream *substream, int cmd,
>  		regmap_update_bits(esai_priv->regmap, REG_ESAI_xCR(tx),
>  				   tx ? ESAI_xCR_TE_MASK : ESAI_xCR_RE_MASK,
>  				   tx ? ESAI_xCR_TE(pins) : ESAI_xCR_RE(pins));
> +		mask = tx ? esai_priv->tx_mask : esai_priv->rx_mask;
> +

Please add a line of brief comments for the reason why we are doing
this here, something similar to the commit log, but should have:
1) Clear xSMA/B 2) Set TE/RE before xSMA/B 3)Set xSMB before xSMA.

Apparently having this mask settings in the trigger() does not look
very common, so I believe a line of comments would help a lot.

You may add my Acked-by in your next version:

Acked-by: Nicolin Chen <nicoleotsuka at gmail.com>

Thanks

> +		regmap_update_bits(esai_priv->regmap, REG_ESAI_xSMB(tx),
> +				   ESAI_xSMB_xS_MASK, ESAI_xSMB_xS(mask));
> +		regmap_update_bits(esai_priv->regmap, REG_ESAI_xSMA(tx),
> +				   ESAI_xSMA_xS_MASK, ESAI_xSMA_xS(mask));
> +
>  		break;
>  	case SNDRV_PCM_TRIGGER_SUSPEND:
>  	case SNDRV_PCM_TRIGGER_STOP:
>  	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
>  		regmap_update_bits(esai_priv->regmap, REG_ESAI_xCR(tx),
>  				   tx ? ESAI_xCR_TE_MASK : ESAI_xCR_RE_MASK, 0);
> +		regmap_update_bits(esai_priv->regmap, REG_ESAI_xSMA(tx),
> +				   ESAI_xSMA_xS_MASK, 0);
> +		regmap_update_bits(esai_priv->regmap, REG_ESAI_xSMB(tx),
> +				   ESAI_xSMB_xS_MASK, 0);
>