[alsa-devel] PLL computation in TLV320AIC3x SoC driver
Vladimir Barinov
vova.barinov at gmail.com
Tue Dec 8 16:46:31 CET 2009
Peter Meerwald wrote:
> 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
>
Correct.
> 2. d should actually be 5125 and not 5120
>
Now I see, I've verified your code handles this. This actually produce
more accuracy for FSREF.
I just tested your patch works fine with sysclk=16384000 and 12288000
but fails with 11286900: it returns FSREF=45467 instead of desired
44100. I think that this is a valuable difference. Please check it.
Regards,
Vladimir
> 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);
>>>
>>>
>>>
>
>
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