On Thu, Apr 07, 2022 at 01:09:37PM +0800, Shengjiu Wang wrote:
> On Tue, Apr 5, 2022 at 4:00 PM Sascha Hauer <[1]s.hauer@xxxxxxxxxxxxxx>
> wrote:
>
> The reference manual has this for calculating the micfil internal clock
> divider:
>
> MICFIL Clock rate
> clkdiv = -----------------
> 8 * OSR * outrate
>
> (with OSR == Oversampling Rate, outrate == output sample rate)
>
> The driver first sets the MICFIL Clock rate to (outrate * 1024) and then
> calculates back the clkdiv value from the above calculation.
>
> Simplify this by using a fixed clkdiv value of 8 and set the MICFIL
> Clock rate to (outrate * clkdiv * OSR * 8).
>
> While at it drop disabling the clock before setting its rate. The MICFIL
> module is disabled when the rate is changed and it is also resetted
> before it is started again, so I doubt it's necessary to disable the
> clock.
>
> Signed-off-by: Sascha Hauer <[2]s.hauer@xxxxxxxxxxxxxx>
> ---
> sound/soc/fsl/fsl_micfil.c | 45 ++++----------------------------------
> 1 file changed, 4 insertions(+), 41 deletions(-)
>
> diff --git a/sound/soc/fsl/fsl_micfil.c b/sound/soc/fsl/fsl_micfil.c
> index 8335646a84d17..fd3b168a38661 100644
> --- a/sound/soc/fsl/fsl_micfil.c
> +++ b/sound/soc/fsl/fsl_micfil.c
> @@ -111,19 +111,6 @@ static const struct snd_kcontrol_new
> fsl_micfil_snd_controls[] = {
> snd_soc_get_enum_double, snd_soc_put_enum_double),
> };
>
> -static inline int get_clk_div(struct fsl_micfil *micfil,
> - unsigned int rate)
> -{
> - long mclk_rate;
> - int clk_div;
> -
> - mclk_rate = clk_get_rate(micfil->mclk);
> -
> - clk_div = mclk_rate / (rate * micfil->osr * 8);
> -
> - return clk_div;
> -}
> -
> /* The SRES is a self-negated bit which provides the CPU with the
> * capability to initialize the PDM Interface module through the
> * slave-bus interface. This bit always reads as zero, and this
> @@ -147,24 +134,6 @@ static int fsl_micfil_reset(struct device *dev)
> return 0;
> }
>
> -static int fsl_micfil_set_mclk_rate(struct fsl_micfil *micfil,
> - unsigned int freq)
> -{
> - struct device *dev = &micfil->pdev->dev;
> - int ret;
> -
> - clk_disable_unprepare(micfil->mclk);
> -
> - ret = clk_set_rate(micfil->mclk, freq * 1024);
> - if (ret)
> - dev_warn(dev, "failed to set rate (%u): %d\n",
> - freq * 1024, ret);
> -
> - clk_prepare_enable(micfil->mclk);
> -
> - return ret;
> -}
> -
> static int fsl_micfil_startup(struct snd_pcm_substream *substream,
> struct snd_soc_dai *dai)
> {
> @@ -238,13 +207,12 @@ static int fsl_micfil_trigger(struct
> snd_pcm_substream *substream, int cmd,
> static int fsl_set_clock_params(struct device *dev, unsigned int rate)
> {
> struct fsl_micfil *micfil = dev_get_drvdata(dev);
> - int clk_div;
> + int clk_div = 8;
> int ret;
>
> - ret = fsl_micfil_set_mclk_rate(micfil, rate);
> - if (ret < 0)
> - dev_err(dev, "failed to set mclk[%lu] to rate %u\n",
> - clk_get_rate(micfil->mclk), rate);
> + ret = clk_set_rate(micfil->mclk, rate * clk_div * micfil->osr *
> 8);
>
> Please make sure micfil->osr is assigned.
Should also be MICFIL_OSR_DEFAULT instead. The micfil->osr field sneaked
in during development and I decided against it finally.
Sascha
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