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SubjectRe: [PATCH 20/25] ASoC: sun8i-codec: Protect the clock rate while streams are open
On Wed, Sep 30, 2020 at 09:11:43PM -0500, Samuel Holland wrote:
> The codec's clock input is shared among all AIFs, and shared with other
> audio-related hardware in the SoC, including I2S and SPDIF controllers.
> To ensure sample rates selected by userspace or by codec2codec DAI links
> are maintained, the clock rate must be protected while it is in use.
>
> Signed-off-by: Samuel Holland <samuel@sholland.org>
> ---
> sound/soc/sunxi/sun8i-codec.c | 25 ++++++++++++++++++++++---
> 1 file changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/sound/soc/sunxi/sun8i-codec.c b/sound/soc/sunxi/sun8i-codec.c
> index 501af64d43a0..86065bee7cd3 100644
> --- a/sound/soc/sunxi/sun8i-codec.c
> +++ b/sound/soc/sunxi/sun8i-codec.c
> @@ -416,27 +416,32 @@ static int sun8i_codec_get_lrck_div_order(unsigned int slots,
> unsigned int div = slots * slot_width;
>
> if (div < 16 || div > 256)
> return -EINVAL;
>
> return order_base_2(div);
> }
>
> +static unsigned int sun8i_codec_get_sysclk_rate(unsigned int sample_rate)
> +{
> + return sample_rate % 4000 ? 22579200 : 24576000;
> +}
> +
> static int sun8i_codec_hw_params(struct snd_pcm_substream *substream,
> struct snd_pcm_hw_params *params,
> struct snd_soc_dai *dai)
> {
> struct sun8i_codec *scodec = snd_soc_dai_get_drvdata(dai);
> struct sun8i_codec_aif *aif = &scodec->aifs[dai->id];
> unsigned int sample_rate = params_rate(params);
> unsigned int slots = aif->slots ?: params_channels(params);
> unsigned int slot_width = aif->slot_width ?: params_width(params);
> - unsigned int sysclk_rate = clk_get_rate(scodec->clk_module);
> - int lrck_div_order, word_size;
> + unsigned int sysclk_rate = sun8i_codec_get_sysclk_rate(sample_rate);
> + int lrck_div_order, ret, word_size;
> u8 bclk_div;
>
> /* word size */
> switch (params_width(params)) {
> case 8:
> word_size = 0x0;
> break;
> case 16:
> @@ -466,17 +471,30 @@ static int sun8i_codec_hw_params(struct snd_pcm_substream *substream,
> (lrck_div_order - 4) << SUN8I_AIF1CLK_CTRL_AIF1_LRCK_DIV);
>
> /* BCLK divider (SYSCLK/BCLK ratio) */
> bclk_div = sun8i_codec_get_bclk_div(sysclk_rate, lrck_div_order, sample_rate);
> regmap_update_bits(scodec->regmap, SUN8I_AIF1CLK_CTRL,
> SUN8I_AIF1CLK_CTRL_AIF1_BCLK_DIV_MASK,
> bclk_div << SUN8I_AIF1CLK_CTRL_AIF1_BCLK_DIV);
>
> - if (!aif->open_streams) {
> + /* SYSCLK rate */
> + if (aif->open_streams) {
> + ret = clk_set_rate(scodec->clk_module, sysclk_rate);
> + if (ret < 0)
> + return ret;
> + } else {
> + ret = clk_set_rate_exclusive(scodec->clk_module, sysclk_rate);

It's not really clear to me why we wouldn't want to always protect the
clock rate here?

> + if (ret == -EBUSY)
> + dev_err(dai->dev, "%s: clock is busy! Sample rate %u Hz "
> + "conflicts with other audio streams.\n",

This string creates a checkpatch warning.

Maxime
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