linux-kernel - Re: [PATCH] ASoC: wm8804: Allow control of master clock divider in PLL generation

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Date:	Fri, 17 Jan 2014 17:43:14 +0100
From:	Florian Meier <florian.meier@...lo.de>
To:	Daniel Matuschek <daniel@...uschek.net>,
	alsa-devel@...a-project.org
CC:	Dimitris.Papastamos@...fsonmicro.com, lgirdwood@...il.com,
	broonie@...nel.org, perex@...ex.cz, tiwai@...e.de,
	patches@...nsource.wolfsonmicro.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: wm8804: Allow control of master clock divider in
 PLL generation

I have tested your patch.
There is a (non blocking) error message regarding .idle_bias_off, but I
assume that should not have something to do with your patch. Can we just
set idle_bias_off to false here?

Otherwise, it looks good to me.

On 01/14/2014 08:34 PM, Daniel Matuschek wrote:
> WM8804 can run with PLL frequencies of 256xfs and 128xfs for
> most sample rates. At 192kHz only 128xfs is supported. The
> existing driver selects 128xfs automatically for some lower
> samples rates. By using an additional mclk_div divider, it
> is now possible to control the behaviour. This allows using
> 256xfs PLL frequency on all sample rates up to 96kHz. It
> should allow lower jitter and better signal quality. The
> behavior has to be controlled by the sound card driver,
> because some sample frequency share the same setting. e.g.
> 192kHz and 96kHz use 24.576MHz master clock. The only
> difference is the MCLK divider.
> 
> Signed-off-by: Daniel Matuschek <daniel@...uschek.net>
> 
> ---
>  sound/soc/codecs/wm8804.c |   17 ++++++++++++++---
>  sound/soc/codecs/wm8804.h |    4 ++++
>  2 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/soc/codecs/wm8804.c b/sound/soc/codecs/wm8804.c
> index 1704b1e..4619bf8 100644
> --- a/sound/soc/codecs/wm8804.c
> +++ b/sound/soc/codecs/wm8804.c
> @@ -63,6 +63,7 @@ struct wm8804_priv {
>      struct regmap *regmap;
>      struct regulator_bulk_data supplies[WM8804_NUM_SUPPLIES];
>      struct notifier_block disable_nb[WM8804_NUM_SUPPLIES];
> +    int mclk_div;
>  };
> 
>  static int txsrc_get(struct snd_kcontrol *kcontrol,
> @@ -318,7 +319,7 @@ static struct {
> 
>  #define FIXED_PLL_SIZE ((1ULL << 22) * 10)
>  static int pll_factors(struct pll_div *pll_div, unsigned int target,
> -               unsigned int source)
> +               unsigned int source, unsigned int mclk_div)
>  {
>      u64 Kpart;
>      unsigned long int K, Ndiv, Nmod, tmp;
> @@ -330,7 +331,8 @@ static int pll_factors(struct pll_div *pll_div,
> unsigned int target,
>       */
>      for (i = 0; i < ARRAY_SIZE(post_table); i++) {
>          tmp = target * post_table[i].div;
> -        if (tmp >= 90000000 && tmp <= 100000000) {
> +        if ((tmp >= 90000000 && tmp <= 100000000) &&
> +            (mclk_div == post_table[i].mclkdiv)) {
>              pll_div->freqmode = post_table[i].freqmode;
>              pll_div->mclkdiv = post_table[i].mclkdiv;
>              target *= post_table[i].div;
> @@ -387,8 +389,12 @@ static int wm8804_set_pll(struct snd_soc_dai *dai,
> int pll_id,
>      } else {
>          int ret;
>          struct pll_div pll_div;
> +        struct wm8804_priv *wm8804;
> 
> -        ret = pll_factors(&pll_div, freq_out, freq_in);
> +        wm8804 = snd_soc_codec_get_drvdata(codec);
> +
> +        ret = pll_factors(&pll_div, freq_out, freq_in,
> +            wm8804->mclk_div);
>          if (ret)
>              return ret;
> 
> @@ -452,6 +458,7 @@ static int wm8804_set_clkdiv(struct snd_soc_dai *dai,
>                   int div_id, int div)
>  {
>      struct snd_soc_codec *codec;
> +    struct wm8804_priv *wm8804;
> 
>      codec = dai->codec;
>      switch (div_id) {
> @@ -459,6 +466,10 @@ static int wm8804_set_clkdiv(struct snd_soc_dai *dai,
>          snd_soc_update_bits(codec, WM8804_PLL5, 0x30,
>                      (div & 0x3) << 4);
>          break;
> +    case WM8804_MCLK_DIV:
> +        wm8804 = snd_soc_codec_get_drvdata(codec);
> +        wm8804->mclk_div = div;
> +        break;
>      default:
>          dev_err(dai->dev, "Unknown clock divider: %d\n", div_id);
>          return -EINVAL;
> diff --git a/sound/soc/codecs/wm8804.h b/sound/soc/codecs/wm8804.h
> index 8ec14f5..e72d4f4 100644
> --- a/sound/soc/codecs/wm8804.h
> +++ b/sound/soc/codecs/wm8804.h
> @@ -57,5 +57,9 @@
>  #define WM8804_CLKOUT_SRC_OSCCLK        4
> 
>  #define WM8804_CLKOUT_DIV            1
> +#define WM8804_MCLK_DIV                2
> +
> +#define WM8804_MCLKDIV_256FS            0
> +#define WM8804_MCLKDIV_128FS            1
> 
>  #endif  /* _WM8804_H */
--
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