linux-kernel - Re: [PATCH v2 03/11] ASoC: fsl

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Date:   Wed, 13 Dec 2017 23:28:51 +0100
From:   "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     broonie@...nel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, alsa-devel@...a-project.org,
        lgirdwood@...il.com, fabio.estevam@....com, timur@...i.org,
        caleb@...me.org, arnaud.mouiche@...oxia.com, lukma@...x.de,
        kernel@...gutronix.de
Subject: Re: [PATCH v2 03/11] ASoC: fsl_ssi: Refine all comments

On 13.12.2017 07:34, Nicolin Chen wrote:
> This patch refines the comments by:
> 1) Removing all out-of-date comments
> 2) Removing all not-so-useful comments
> 3) Unifying the styles of all comments
> 4) Simplifying over-descriptive comments
> 5) Adding comments to improve code readablity
> 6) Moving all register related comments to fsl_ssi.h
> 7) Adding comments to all register and field defines
> 
> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
> ---
> 
> Changelog
> v1->v2
>  * Added some new comments at "SoC specific data" to be more precise.
>  * Revised one comment in fsl_ssi_config().
>  * Revised the comment of fsl_ssi_setup_reg_vals().
>  * Added one comment for AC97 in fsl_ssi_setup_reg_vals().
>  * Revised the comment of fsl_ssi_hw_params() to be more precise.
>  * Added some comments in _fsl_ssi_set_dai_fmt() to help understand the formats.
>  * Added one comment in fsl_ssi_set_dai_fmt() to state why AC97 needs to bypass it.
>  * Revised comments in fsl_ssi_set_dai_tdm_slot() to be more precise.
>  * Revised comments around dual FIFO code in fsl_ssi_imx_probe() to be more precise.
> 
>  sound/soc/fsl/fsl_ssi.c     | 376 ++++++++++++++------------------------------
>  sound/soc/fsl/fsl_ssi.h     |  67 +++++++-
>  sound/soc/fsl/fsl_ssi_dbg.c |  12 +-
>  3 files changed, 188 insertions(+), 267 deletions(-)
> 
> diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c
> index e903c92..796a7ea 100644
> --- a/sound/soc/fsl/fsl_ssi.c
> +++ b/sound/soc/fsl/fsl_ssi.c
(..)
> @@ -878,10 +794,7 @@ static int fsl_ssi_hw_params(struct snd_pcm_substream *substream,
>  	regmap_read(regs, CCSR_SSI_SCR, &scr_val);
>  	enabled = scr_val & CCSR_SSI_SCR_SSIEN;
>  
> -	/*
> -	 * If we're in synchronous mode, and the SSI is already enabled,
> -	 * then STCCR is already set properly.
> -	 */
> +	/* To support simultaneous TX and RX, bypass it if SSI is enabled */
>  	if (enabled && ssi->cpu_dai_drv.symmetric_rates)
>  		return 0;
>  

I would say that the old comment described better what is happening -
since in synchronous (& non-AC'97) mode STCCR controls both TX and RX
the first direction that is started (either playback or capture) is the
only direction that needs to configure SSI in hw_params().

When the opposite direction enters hw_params() (while the first one is
still running) there is no need to do anything and we can exit early.

Maciej