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>
---
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;
--
2.7.4
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