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drm/i2c: tda998x: improve programming of audio divisor

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Improve the selection of the audio clock divisor so that more modes
and sample rates work.

Tested-by: Sven Van Asbroeck <TheSven73@gmail.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Russell King 2019-02-27 00:04:53 +00:00
parent 935b9ca357
commit 7dad3740ae
1 changed files with 28 additions and 16 deletions
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44
drivers/gpu/drm/i2c/tda998x_drv.c
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@ -865,6 +865,32 @@ tda998x_write_avi(struct tda998x_priv *priv, const struct drm_display_mode *mode
/* Audio support */
/*
* The audio clock divisor register controls a divider producing Audio_Clk_Out
* from SERclk by dividing it by 2^n where 0 <= n <= 5. We don't know what
* Audio_Clk_Out or SERclk are. We guess SERclk is the same as TMDS clock.
*
* It seems that Audio_Clk_Out must be the smallest value that is greater
* than 128*fs, otherwise audio does not function. There is some suggestion
* that 126*fs is a better value.
*/
static u8 tda998x_get_adiv(struct tda998x_priv *priv, unsigned int fs)
{
unsigned long min_audio_clk = fs * 128;
unsigned long ser_clk = priv->tmds_clock * 1000;
u8 adiv;
for (adiv = AUDIO_DIV_SERCLK_32; adiv != AUDIO_DIV_SERCLK_1; adiv--)
if (ser_clk > min_audio_clk << adiv)
break;
dev_dbg(&priv->hdmi->dev,
"ser_clk=%luHz fs=%uHz min_aclk=%luHz adiv=%d\n",
ser_clk, fs, min_audio_clk, adiv);
return adiv;
}
static void tda998x_audio_mute(struct tda998x_priv *priv, bool on)
{
if (on) {
@ -882,6 +908,8 @@ static int tda998x_configure_audio(struct tda998x_priv *priv,
u8 buf[6], clksel_aip, clksel_fs, cts_n, adiv;
u32 n;
adiv = tda998x_get_adiv(priv, settings->params.sample_rate);
/* Enable audio ports */
reg_write(priv, REG_ENA_AP, settings->params.config);
@ -926,22 +954,6 @@ static int tda998x_configure_audio(struct tda998x_priv *priv,
reg_clear(priv, REG_AIP_CNTRL_0, AIP_CNTRL_0_LAYOUT |
AIP_CNTRL_0_ACR_MAN); /* auto CTS */
reg_write(priv, REG_CTS_N, cts_n);
/*
* Audio input somehow depends on HDMI line rate which is
* related to pixclk. Testing showed that modes with pixclk
* >100MHz need a larger divider while <40MHz need the default.
* There is no detailed info in the datasheet, so we just
* assume 100MHz requires larger divider.
*/
adiv = AUDIO_DIV_SERCLK_8;
if (priv->tmds_clock > 100000)
adiv++; /* AUDIO_DIV_SERCLK_16 */
/* S/PDIF asks for a larger divider */
if (settings->params.format == AFMT_SPDIF)
adiv++; /* AUDIO_DIV_SERCLK_16 or _32 */
reg_write(priv, REG_AUDIO_DIV, adiv);
/*