On 22/02/2019 23:27, Russell King wrote:
> It appears that TDA998x derives the CTS value using the supplied I2S
> bit clock (BCLK) rather than 128·fs. TDA998x uses two constants named
> m and k in the CTS generator such that we have this relationship
> between the source BCLK and the sink fs:
>
> 128·fs_sink = BCLK·m / k
>
> Where BCLK = bclk_ratio·fs_source.
>
> We have been lucky up to now that all users have scaled their bclk_ratio
> to match the sample width - for example, on Beagle Bone Black, with a
> 16-bit sample width, BCLK = 32·fs, which increases to 64·fs for 32-bit
> samples. 24-bit samples are sent as 32-bit.
>
> We are now starting to see users whose I2S blocks send at 64·fs for
> 16-bit samples, which means TDA998x now breaks.
>
> ASoC has a snd_soc_dai_set_bclk_ratio() call available which sets the
> ratio of BCLK to the sample rate. Implement support for this.
>
> Signed-off-by: Russell King <rmk+ker...@armlinux.org.uk>
Works at least on Beaglebone-black.
Tested-by: Jyri Sarha <jsa...@ti.com>
Reviewed-by: Jyri Sarha <jsa...@ti.com>
> ---
> drivers/gpu/drm/i2c/tda998x_drv.c | 20 +++++++++++++-------
> include/drm/i2c/tda998x.h | 1 +
> 2 files changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c
> b/drivers/gpu/drm/i2c/tda998x_drv.c
> index 645d884fb9e8..f2d40235acf9 100644
> --- a/drivers/gpu/drm/i2c/tda998x_drv.c
> +++ b/drivers/gpu/drm/i2c/tda998x_drv.c
> @@ -895,21 +895,26 @@ tda998x_configure_audio(struct tda998x_priv *priv,
> reg_write(priv, REG_MUX_AP, MUX_AP_SELECT_I2S);
> clksel_aip = AIP_CLKSEL_AIP_I2S;
> clksel_fs = AIP_CLKSEL_FS_ACLK;
> - switch (params->sample_width) {
> + switch (params->bclk_ratio) {
> case 16:
> + cts_n = CTS_N_M(3) | CTS_N_K(0);
> + break;
> + case 32:
> cts_n = CTS_N_M(3) | CTS_N_K(1);
> break;
> - case 18:
> - case 20:
> - case 24:
> + case 48:
> cts_n = CTS_N_M(3) | CTS_N_K(2);
> break;
> - default:
> - case 32:
> + case 64:
> cts_n = CTS_N_M(3) | CTS_N_K(3);
> break;
> + case 128:
> + cts_n = CTS_N_M(0) | CTS_N_K(0);
> + break;
> + default:
> + dev_err(&priv->hdmi->dev, "unsupported I2S bclk
> ratio\n");
> + return -EINVAL;
> }
> -
> switch (params->format & AFMT_I2S_MASK) {
> case AFMT_I2S_LEFT_J:
> i2s_fmt = I2S_FORMAT_LEFT_J;
> @@ -997,6 +1002,7 @@ static int tda998x_audio_hw_params(struct device *dev,
> void *data,
> struct tda998x_priv *priv = dev_get_drvdata(dev);
> int i, ret;
> struct tda998x_audio_params audio = {
> + .bclk_ratio = daifmt->bclk_ratio,
> .sample_width = params->sample_width,
> .sample_rate = params->sample_rate,
> .cea = params->cea,
> diff --git a/include/drm/i2c/tda998x.h b/include/drm/i2c/tda998x.h
> index b0864f0be017..4e0f0cd2d428 100644
> --- a/include/drm/i2c/tda998x.h
> +++ b/include/drm/i2c/tda998x.h
> @@ -19,6 +19,7 @@ enum {
> struct tda998x_audio_params {
> u8 config;
> u8 format;
> + u8 bclk_ratio;
> unsigned sample_width;
> unsigned sample_rate;
> struct hdmi_audio_infoframe cea;
>
--
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