[alsa-devel] PLL computation in TLV320AIC3x SoC driver
Peter Meerwald
pmeerw at pmeerw.net
Tue Dec 8 16:12:08 CET 2009
Hello Vladimir,
> > I'm trying to use the SoC TLV320AIC3x codec driver with sysclk 16384000 and
> > ran into some problems with setting PLL; below is a patch against
> > linux-2.6-asoc
> I've made the simple test application to calculate pll_p/r/j/d values using
> current tlv320aic3x clock calculation scheme and I've got:
> samplerate=8000: pll_p=1, pll_r=1, pll_j=6, pll_d=0, hence FSREF=(sysclk *
> [pll_j].[pll_d] * pll_r) / (2048 * pll_p) = 48000
> samplerate=11025: pll_p=1, pll_r=1, pll_j=5, pll_d=5120, hence FSREF= 44096
> samplerate=16000: pll_p=1, pll_r=1, pll_j=6, pll_d=0, hence FSREF=48000
> samplerate=22050: pll_p=1, pll_r=1, pll_j=5, pll_d=5120, hence FSREF= 44096
> samplerate=32000: pll_p=1, pll_r=1, pll_j=6, pll_d=0, hence FSREF=48000
> samplerate=44100: pll_p=1, pll_r=1, pll_j=5, pll_d=5120, hence FSREF= 44096
> samplerate=48000: pll_p=1, pll_r=1, pll_j=6, pll_d=0, hence FSREF=48000
> samplerate=64000: pll_p=1, pll_r=1, pll_j=6, pll_d=0, hence FSREF=48000, note
> that here we used DUAL_RATE_MODE, hence FSREF=96000
> samplerate=88200: pll_p=1, pll_r=1, pll_j=5, pll_d=5120, hence FSREF= 44096,
> note that here we used DUAL_RATE_MODE hence FSREF=88192
> samplerate=96000: pll_p=1, pll_r=1, pll_j=6, pll_d=0, hence FSREF=48000, note
> that here we used DUAL_RATE_MODE hence FSREF = 96000
> Hence according to current code the calculations of desired FSREF is correct
> for sysclk=16384000
> I've not tried it with your patch since I don't actually understand what do
> you fix? :)
1. loop variables are r and p but for computation of j the variables
pll_r and pll_p are used; I think r and p should be used in the
computation of j, your code below:
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;
further, the codec datasheet mandates certain ranges for 'good
performance', 4 <= j <= 55 (for d==0) and 4 <= j <= 11 (for d!=0) which
are not checked for
2. d should actually be 5125 and not 5120
3. appropriate is spell appropriately :)
> > note that the original code uses variables pll_r and pll_p instead of the
> > loop variable r and p to compute tmp, this seems broken
> >
> > further, the original code does not respect the constraints on j (>= 4, <=
> > 55 for d==0) according to the codec's datasheet, and similarly for d!=0
> >
> > I've tested the code with a number of reasonable sysclk values and got sane
> > PLL values; please apply if acceptable
> > thanks, regards, p.
> >
> >
> > diff --git a/sound/soc/codecs/tlv320aic3x.c b/sound/soc/codecs/tlv320aic3x.c
> > index 3395cf9..e84e473 100644
> > --- a/sound/soc/codecs/tlv320aic3x.c
> > +++ b/sound/soc/codecs/tlv320aic3x.c
> > @@ -766,9 +766,10 @@ 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 =
> > @@ -835,47 +836,62 @@ static int aic3x_hw_params(struct snd_pcm_substream
> > *substream,
> > 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.
> > + * find an appropriate setup for j, d, r and p by iterating over
> > + * p, r and j first, then trying to compute the fraction d.
> > + * Up to 6528 values are probed, the closest one wins the game.
> > * 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;
> > -
> > - if (j > 63)
> > - continue;
> > -
> > - 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)
> > - break;
> > - }
> > + for (r = 1; r <= 16; r++)
> > + for (p = 1; p <= 8; p++) {
> > + 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;
> > +
> > + /* 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;
> > + }
> > +
> > + /* Early exit for exact matches */
> > + if (clk == codec_clk)
> > + goto found;
> > + }
> > + }
> > +
> > + /* 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 * fsref * 10) / (aic3x->sysclk / 1000)) % 10000;
> > + 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 = 1;
> > + 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);
> >
> >
--
Peter Meerwald
Kaigasse 3 / 8
A-5020 Salzburg / AUSTRIA
+43-664-2444418 (mobile)
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