Re: [alsa-devel] [PATCH] ASoC: fsl_ssi: call _fsl_ssi_set_dai_fmt() just once in AC'97 mode

[Nicolin Chen]

On Mon, Nov 20, 2017 at 11:13:45PM +0100, Maciej S. Szmigiero wrote:
> In AC'97 mode we configure and start SSI RX / TX on probe path via
> a call to _fsl_ssi_set_dai_fmt() function.
> We don't need to call this function again later and in fact don't want to
> do it since this function temporarily sets STCR, SRCR and SCR to some
> intermediate values.
> 
> We need to make sure, however, that only proper channel slots are enabled
> at playback start time since some AC'97 CODECs (like VT1613) were observed
> requesting via SLOTREQ (and so enabling at SSI) spurious ones just after
> an AC'97 link is started but before the CODEC is configured by its driver.

I don't really understand this part. Why do we need to *make sure*
and set SACCDIS and SACCEN again since they're initialized already?

Could you please elaborate a bit more?

> Theoretically, this should be necessary only for the very first playback
> but let's play safe here and make sure that no extra slots are enabled
> every time a playback is started.
> 
> Signed-off-by: Maciej S. Szmigiero <mail@xxxxxxxxxxxxxxxxxxxxx>
> ---
>  sound/soc/fsl/fsl_ssi.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c
> index 48bb850a34d9..dad80b4b0cfc 100644
> --- a/sound/soc/fsl/fsl_ssi.c
> +++ b/sound/soc/fsl/fsl_ssi.c
> @@ -630,12 +630,6 @@ static void fsl_ssi_setup_ac97(struct fsl_ssi_private *ssi_private)
>  	regmap_write(regs, CCSR_SSI_SACNT,
>  			CCSR_SSI_SACNT_AC97EN | CCSR_SSI_SACNT_FV);
>  
> -	/* no SACC{ST,EN,DIS} regs on imx21-class SSI */
> -	if (!ssi_private->soc->imx21regs) {
> -		regmap_write(regs, CCSR_SSI_SACCDIS, 0xff);
> -		regmap_write(regs, CCSR_SSI_SACCEN, 0x300);
> -	}

> @@ -1149,9 +1146,16 @@ static int fsl_ssi_trigger(struct snd_pcm_substream *substream, int cmd,
>  	case SNDRV_PCM_TRIGGER_START:
>  	case SNDRV_PCM_TRIGGER_RESUME:
>  	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
> -		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
> +		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
> +			/* no SACC{ST,EN,DIS} regs on imx21-class SSI */
> +			if (fsl_ssi_is_ac97(ssi_private) &&
> +				!ssi_private->soc->imx21regs) {
> +				regmap_write(regs, CCSR_SSI_SACCDIS, 0xff);
> +				regmap_write(regs, CCSR_SSI_SACCEN, 0x300);
> +			}

And second, why could we ignore them for STREAM_CAPTURE here?

Well, at least this part could be moved into fsl_ssi_tx_config()
since we have an abstraction layer of register configurations.

Thanks
Nic

> +
>  			fsl_ssi_tx_config(ssi_private, true);
> -		else
> +		} else
>  			fsl_ssi_rx_config(ssi_private, true);
>  		break;
>  
> 
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