Re: PLL computation in TLV320AIC3x SoC driver

[Vladimir Barinov <vova.barinov@gmail.com>]

Hello Peter,

Peter Meerwald wrote:
> Hello,
>
>   
>>>>>> 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 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.
>>>       
>> Please check  also 33868800  sysclk, it  returns  FSREF=47545 instead of
>> 48000.
>>     
>
> I have put the proposed code at http://pmeerw.net/clk/ for review;
>
>
>   
> note that the proposed code has less deviation from fsref in all cases and 
> manages to stay within recommended settings for sysclk 33868800 
>
> I have modified the following line to get rid of rounding errors as much 
> as possible:
> /* do not use codec_clk here since we'd loose precision */
> d = ((2048 * p * fsref) - j * sysclk) * 100 / (sysclk/100);
> and fixed a bug which always set pll_p = 1 in case d!=0
>
>   
I confirm that it handles all cases with best precision now.
> if code looks good, I'll submit a patch against linux-sound-2.6 as Mark 
> suggested
>
>   
I'm ok to submit.