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ASoC: PLL computation in TLV320AIC3x SoC driver

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fix precision of PLL computation for TLV320AIC3x SoC driver,
test results are at http://pmeerw.net/clk

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Acked-by: Vladimir Barinov <vova.barinov@gmail.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
This commit is contained in:
Peter Meerwald 2009-12-14 14:44:56 +01:00 committed by Mark Brown
parent 3497b91946
commit 255173b40d
1 changed files with 51 additions and 28 deletions
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79
sound/soc/codecs/tlv320aic3x.c
View file

@ -765,9 +765,10 @@ static int aic3x_hw_params(struct snd_pcm_substream *substream,
struct snd_soc_codec *codec = socdev->card->codec;
struct aic3x_priv *aic3x = codec->private_data;
int codec_clk = 0, bypass_pll = 0, fsref, last_clk = 0;
u8 data, r, p, pll_q, pll_p = 1, pll_r = 1, pll_j = 1;
u16 pll_d = 1;
u8 data, j, r, p, pll_q, pll_p = 1, pll_r = 1, pll_j = 1;
u16 d, pll_d = 1;
u8 reg;
int clk;
/* select data word length */
data =
@ -833,48 +834,70 @@ static int aic3x_hw_params(struct snd_pcm_substream *substream,
if (bypass_pll)
return 0;
/* Use PLL
* find an apropriate setup for j, d, r and p by iterating over
* p and r - j and d are calculated for each fraction.
* Up to 128 values are probed, the closest one wins the game.
/* Use PLL, compute apropriate setup for j, d, r and p, the closest
* one wins the game. Try with d==0 first, next with d!=0.
* Constraints for j are according to the datasheet.
* The sysclk is divided by 1000 to prevent integer overflows.
*/
codec_clk = (2048 * fsref) / (aic3x->sysclk / 1000);
for (r = 1; r <= 16; r++)
for (p = 1; p <= 8; p++) {
int clk, tmp = (codec_clk * pll_r * 10) / pll_p;
u8 j = tmp / 10000;
u16 d = tmp % 10000;
for (j = 4; j <= 55; j++) {
/* This is actually 1000*((j+(d/10000))*r)/p
* The term had to be converted to get
* rid of the division by 10000; d = 0 here
*/
int clk = (1000 * j * r) / p;
if (j > 63)
continue;
/* Check whether this values get closer than
* the best ones we had before
*/
if (abs(codec_clk - clk) <
abs(codec_clk - last_clk)) {
pll_j = j; pll_d = 0;
pll_r = r; pll_p = p;
last_clk = clk;
}
if (d != 0 && aic3x->sysclk < 10000000)
continue;
/* This is actually 1000 * ((j + (d/10000)) * r) / p
* The term had to be converted to get rid of the
* division by 10000 */
clk = ((10000 * j * r) + (d * r)) / (10 * p);
/* check whether this values get closer than the best
* ones we had before */
if (abs(codec_clk - clk) < abs(codec_clk - last_clk)) {
pll_j = j; pll_d = d; pll_r = r; pll_p = p;
last_clk = clk;
/* Early exit for exact matches */
if (clk == codec_clk)
goto found;
}
/* Early exit for exact matches */
if (clk == codec_clk)
break;
}
/* try with d != 0 */
for (p = 1; p <= 8; p++) {
j = codec_clk * p / 1000;
if (j < 4 || j > 11)
continue;
/* do not use codec_clk here since we'd loose precision */
d = ((2048 * p * fsref) - j * aic3x->sysclk)
* 100 / (aic3x->sysclk/100);
clk = (10000 * j + d) / (10 * p);
/* check whether this values get closer than the best
* ones we had before */
if (abs(codec_clk - clk) < abs(codec_clk - last_clk)) {
pll_j = j; pll_d = d; pll_r = 1; pll_p = p;
last_clk = clk;
}
/* Early exit for exact matches */
if (clk == codec_clk)
goto found;
}
if (last_clk == 0) {
printk(KERN_ERR "%s(): unable to setup PLL\n", __func__);
return -EINVAL;
}
found:
data = aic3x_read_reg_cache(codec, AIC3X_PLL_PROGA_REG);
aic3x_write(codec, AIC3X_PLL_PROGA_REG, data | (pll_p << PLLP_SHIFT));
aic3x_write(codec, AIC3X_OVRF_STATUS_AND_PLLR_REG, pll_r << PLLR_SHIFT);