linux-kernel - Re: [PATCH V3 1/2] ASoC: fsl_asrc: replace the process

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Date:   Thu, 18 Apr 2019 08:50:48 +0000
From:   "S.j. Wang" <shengjiu.wang@....com>
To:     Nicolin Chen <nicoleotsuka@...il.com>
CC:     "timur@...nel.org" <timur@...nel.org>,
        "Xiubo.Lee@...il.com" <Xiubo.Lee@...il.com>,
        "festevam@...il.com" <festevam@...il.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 1/2] ASoC: fsl_asrc: replace the process_option table
 with function

Hi

> 
> 
> On Thu, Apr 18, 2019 at 02:37:03AM +0000, S.j. Wang wrote:
> > > Here:
> > > > +     /* Does not support cases: Tsout > 8.125 * Tsin */
> > > > +     if (inrate * 8 > 65 * outrate)
> 
> Though it might not matter any more (see my last comments), it should be
> "inrate > 8.125 * outrate" in the comments.
> 
> > > > +             return -EINVAL;
> > > And here:
> > > > +     ret = fsl_asrc_sel_proc(inrate, outrate, &pre_proc, &post_proc);
> > > > +     if (ret) {
> > > > +             pair_err("No supported pre-processing options\n");
> > > > +             return ret;
> > > > +     }
> > >
> > > Instead of a general message, I was thinking of a more specific one
> > > by telling users that the ratio between the two rates isn't
> > > supported -- something similar to what I suggested previously:
> > >
> > >         pair_err("Does not support %d (input) > 8.125 * %d (output)\n",
> > >                  outrate, inrate);
> > >
> 
> > In fsl_asrc_sel_proc,  we can't call the pair_err for there is no
> > struct fsl_asrc_pair *pair in the argument. Do you think we need to
> > add this argument?
> 
> I's thinking of adding it to the top of fsl_asrc_config_pair() as a part of
> inrate-outrate-validation, however, I found that actually we already have a
> similar check in the early routine:
>         if ((outrate > 8000 && outrate < 30000) &&
>             (outrate/inrate > 24 || inrate/outrate > 8)) {
>                 pair_err("exceed supported ratio range [1/24, 8] for \
>                          inrate/outrate: %d/%d\n", inrate, outrate);
>                 return -EINVAL;
>         }
> 
> And this is according to IMX6DQRM:
>     Limited support for the case when output sampling rates is
>     between 8kHz and 30kHz. The limitation is the supported ratio
>     (Fsin/Fsout) range as between 1/24 to 8
> 
> This should cover your 8.125 condition already, even if having an outrate
> range between [8KHz, 30KHz] check, since an outrate above 30KHz will not
> have an inrate bigger than 8.125 times of it, given the maximum input rate
> is 192KHz.
> 
> So I think that we can just drop that 8.125 condition from your change and
> there's no need to error out any more.
> 
No, if outrate=8kHz,  inrate > 88.2kHz, these cases are not supported. 
This is not covered by

        if ((outrate > 8000 && outrate < 30000) &&
            (outrate/inrate > 24 || inrate/outrate > 8)) {

> However, we do need a patch to fix a potential rounding issue:
> -           (outrate/inrate > 24 || inrate/outrate > 8)) {
> +           (outrate > 24 * inrate || inrate > 8 * outrate)) {
> 
> Should fix the missing whitespace also. And it will be needed to send to
> stable kernel too. Will you help submit a change?
> 
> Thanks