Subject: Re: [alsa-devel] [RFC][PATCH v1] ASoC: fsl_ssi: Add DAI master mode support for SSI on i.MX series

From: Nicolin Chen <[email-masked]>
Date: Fri, 13 Jun 2014 16:56:03 +0800

On Fri, Jun 13, 2014 at 11:00:01AM +0200, Takashi Iwai wrote:
> At Thu, 12 Jun 2014 22:24:55 -0500,
> Timur Tabi wrote:
> > 
> > On Thu, Dec 12, 2013 at 4:44 AM, Nicolin Chen
> > <[email-masked]> wrote:
> > >
> > > +static int fsl_ssi_set_dai_sysclk(struct snd_soc_dai *cpu_dai,
> > > +                                 int clk_id, unsigned int freq, int dir)
> > > +{
> > > +       struct fsl_ssi_private *ssi_private = snd_soc_dai_get_drvdata(cpu_dai);
> > > +       struct ccsr_ssi __iomem *ssi = ssi_private->ssi;
> > > +       int synchronous = ssi_private->cpu_dai_drv.symmetric_rates, ret;
> > > +       u32 pm = 999, div2, psr, stccr, mask, afreq, factor, i;
> > > +       unsigned long flags, clkrate, baudrate, tmprate;
> > > +       u64 sub, savesub = 100000;
> > > +
> > > +       /* Don't apply it to any non-baudclk circumstance */
> > > +       if (IS_ERR(ssi_private->baudclk))
> > > +               return -EINVAL;
> > > +
> > > +       /* It should be already enough to divide clock by setting pm alone */
> > > +       psr = 0;
> > > +       div2 = 0;
> > > +
> > > +       factor = (div2 + 1) * (7 * psr + 1) * 2;
> > > +
> > > +       for (i = 0; i < 255; i++) {
> > > +               /* The bclk rate must be smaller than 1/5 sysclk rate */
> > > +               if (factor * (i + 1) < 5)
> > > +                       continue;
> > > +
> > > +               tmprate = freq * factor * (i + 2);
> > > +               clkrate = clk_round_rate(ssi_private->baudclk, tmprate);
> > > +
> > > +               do_div(clkrate, factor);
> > 
> > This do_div() call causes this warning on PowerPC:
> > 
> >   CC      sound/soc/fsl/fsl_ssi.o
> > sound/soc/fsl/fsl_ssi.c: In function 'fsl_ssi_set_bclk':
> > sound/soc/fsl/fsl_ssi.c:593:3: warning: comparison of distinct pointer
> > types lacks a cast
> > sound/soc/fsl/fsl_ssi.c:593:3: warning: right shift count >= width of type
> > sound/soc/fsl/fsl_ssi.c:593:3: warning: passing argument 1 of
> > '__div64_32' from incompatible pointer type
> > include/asm-generic/div64.h:35:17: note: expected 'uint64_t *' but
> > argument is of type 'long unsigned int *'
> > 
> > The comments in do_div() say that clkrate should be 64-bits.  Changing
> > clkrate to a u64 does fix this problem, but I'm wondering if anyone
> > else has seen this.  This code has been around for months.
> 
> Using do_div() for unsigned long makes no sense.
> And, you *must* pass uint64_t there as an argument, since it's no
> inline function and there is no implicit conversion in the generic
> code.
> 
> In short, use the normal division operator instead:
> 	clkrate /= factor;

Yes. I forgot why I used do_div() for clkrate at the first place
but it's definitely a mistake here.

Sorry,
Nicolin

> Takashi