linux-kernel - Re: [PATCH v5 02/15] ASoC: sun4i-i2s: Add set_tdm

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Date:   Fri, 16 Aug 2019 08:27:05 +0200
From:   Code Kipper <codekipper@...il.com>
To:     Maxime Ripard <maxime.ripard@...tlin.com>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux-ALSA <alsa-devel@...a-project.org>,
        "Andrea Venturi (pers)" <be17068@...rbole.bo.it>
Subject: Re: [PATCH v5 02/15] ASoC: sun4i-i2s: Add set_tdm_slot functionality

On Wed, 14 Aug 2019 at 13:08, Maxime Ripard <maxime.ripard@...tlin.com> wrote:
>
> Hi,
>
> On Wed, Aug 14, 2019 at 08:08:41AM +0200, codekipper@...il.com wrote:
> > From: Marcus Cooper <codekipper@...il.com>
> >
> > Codecs without a control connection such as i2s based HDMI audio and
> > the Pine64 DAC require a different amount of bit clocks per frame than
> > what is calculated by the sample width. Use the tdm slot bindings to
> > provide this mechanism.
> >
> > Signed-off-by: Marcus Cooper <codekipper@...il.com>
> > ---
> >  sound/soc/sunxi/sun4i-i2s.c | 23 +++++++++++++++++++++--
> >  1 file changed, 21 insertions(+), 2 deletions(-)
> >
> > diff --git a/sound/soc/sunxi/sun4i-i2s.c b/sound/soc/sunxi/sun4i-i2s.c
> > index 8201334a059b..7c37b6291df0 100644
> > --- a/sound/soc/sunxi/sun4i-i2s.c
> > +++ b/sound/soc/sunxi/sun4i-i2s.c
> > @@ -195,6 +195,9 @@ struct sun4i_i2s {
> >       struct regmap_field     *field_rxchansel;
> >
> >       const struct sun4i_i2s_quirks   *variant;
> > +
> > +     unsigned int    tdm_slots;
> > +     unsigned int    slot_width;
> >  };
> >
> >  struct sun4i_i2s_clk_div {
> > @@ -346,7 +349,7 @@ static int sun4i_i2s_set_clk_rate(struct snd_soc_dai *dai,
> >       if (i2s->variant->has_fmt_set_lrck_period)
> >               regmap_update_bits(i2s->regmap, SUN4I_I2S_FMT0_REG,
> >                                  SUN8I_I2S_FMT0_LRCK_PERIOD_MASK,
> > -                                SUN8I_I2S_FMT0_LRCK_PERIOD(32));
> > +                                SUN8I_I2S_FMT0_LRCK_PERIOD(word_size));
> >
> >
> >       /* Set sign extension to pad out LSB with 0 */
> >       regmap_field_write(i2s->field_fmt_sext, 0);
> > @@ -450,7 +453,8 @@ static int sun4i_i2s_hw_params(struct snd_pcm_substream *substream,
> >       regmap_field_write(i2s->field_fmt_sr, sr);
> >
> >       return sun4i_i2s_set_clk_rate(dai, params_rate(params),
> > -                                   params_width(params));
> > +                                   i2s->tdm_slots ?
> > +                                   i2s->slot_width : params_width(params));
>
> This is slightly more complicated than that.

At this point we're only supporting 2 channels with fixed slot
settings. I've added a comment to state
that we're using the tdm_slot at the moment as an indicator to
override the slot width. Do you think
that is enough for now?.

Thanks,
CK
>
> On the H3 (and all related ones), the CHAN_CFG_TX_SLOT_NUM and
> _RX_SLOT_NUM fields in the CHAN_CFG register need to be set to the
> number of slots as well.
>
> Maxime
>
> --
> Maxime Ripard, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com