[alsa-devel] [EXT] Re: [PATCH] ASoC: fsl_asrc: replace the process_option table with function

[S.j. Wang]

Hi

> 
> On Wed, Apr 10, 2019 at 03:15:26AM +0000, S.j. Wang wrote:
> > The table is not flexible if supported sample rate is not in the
> > table, so use a function to replace it.
> 
> Could you please elaborate a bit the special use case here?
> 
> The table was copied directly from the Reference Manual. We also have
> listed all supported input and output sample rates just right behind that table.
> If there're missing rates, we probably should update those two lists also?
> Otherwise, how could we have a driver limiting both I/O sample rates while
> we still see something not in the table?
> 

Yes,  I plan to send another patch to update the in/out rate list.  Do I need
To merge that to this commit?  Actually we want to support 12k and 24kHz

> > +static int proc_autosel(int Fsin, int Fsout, int *pre_proc, int
> > +*post_proc)
> 
> Please add some comments to this function to explain what it does, and how
> it works. And better to rename it to something like "fsl_asrc_sel_proc".
> 
Yes, some comments should be added, but not so detail, because this function
Is get from the design team, but the owner has left.

> > +{
> > +     bool det_out_op2_cond;
> > +     bool det_out_op0_cond;
> > +
> > +     det_out_op2_cond = (((Fsin * 15 > Fsout * 16) & (Fsout < 56000)) |
> > +                                     ((Fsin > 56000) & (Fsout < 56000)));
> > +     det_out_op0_cond = (Fsin * 23 < Fsout * 8);
> 
> "detect output option condition"? Please explain a bit or add comments to
> explain.
> 
> > +
> > +     /*
> > +      * Not supported case: Tsout>16.125*Tsin, and Tsout>8.125*Tsin.
> 
> Could be "unsupported". And it should fit within one line:
>         /* Unsupported case: Tsout > 16.125 * Tsin, and Tsout > 8.125 * Tsin */
> 
> > +      */
> > +     if (Fsin * 8 > 129 * Fsout)
> > +             *pre_proc = 5;
> > +     else if (Fsin * 8 > 65 * Fsout)
> > +             *pre_proc = 4;
> > +     else if (Fsin * 8 > 33 * Fsout)
> > +             *pre_proc = 2;
> > +     else if (Fsin * 8 > 15 * Fsout) {
> > +             if (Fsin > 152000)
> > +                     *pre_proc = 2;
> > +             else
> > +                     *pre_proc = 1;
> > +     } else if (Fsin < 76000)
> > +             *pre_proc = 0;
> > +     else if (Fsin > 152000)
> > +             *pre_proc = 2;
> > +     else
> > +             *pre_proc = 1;
> > +
> > +     if (det_out_op2_cond)
> > +             *post_proc = 2;
> > +     else if (det_out_op0_cond)
> > +             *post_proc = 0;
> > +     else
> > +             *post_proc = 1;
> > +
> > +     if (*pre_proc == 4 || *pre_proc == 5)
> > +             return -EINVAL;
> 
> I think you'd better add some necessary comments here too.
> 
> > @@ -377,11 +404,17 @@ static int fsl_asrc_config_pair(struct fsl_asrc_pair
> *pair)
> >                          ASRCTR_IDRi_MASK(index) | ASRCTR_USRi_MASK(index),
> >                          ASRCTR_IDR(index) | ASRCTR_USR(index));
> >
> > +     ret = proc_autosel(inrate, outrate, &pre_proc, &post_proc);
> > +     if (ret) {
> > +             pair_err("No supported pre-processing options\n");
> > +             return ret;
> > +     }
> 
> I think we should do this earlier in this function, once We know the inrate
> and outrate, instead of having all register being configured then going for an
> error-out.

Ok.
> 
> Another thing confuses me: so we could have supported sample rates in the
> list but the hardware might not support some of them because we couldn't
> calculate their processing options?

No, just want to support 12k, 24KHz, or others as customer like.