Re: [linux-sunxi] Re: [PATCH v4 6/9] ASoC: sun4i-i2s: Add multi-lane functionality

[Christopher Obbard <chris@64studio.com>]

On Tue, 4 Jun 2019 at 09:43, Code Kipper <codekipper@gmail.com> wrote:
>
> On Tue, 4 Jun 2019 at 09:58, Maxime Ripard <maxime.ripard@bootlin.com> wrote:
> >
> > On Mon, Jun 03, 2019 at 07:47:32PM +0200, codekipper@gmail.com wrote:
> > > From: Marcus Cooper <codekipper@gmail.com>
> > >
> > > The i2s block supports multi-lane i2s output however this functionality
> > > is only possible in earlier SoCs where the pins are exposed and for
> > > the i2s block used for HDMI audio on the later SoCs.
> > >
> > > To enable this functionality, an optional property has been added to
> > > the bindings.
> > >
> > > Signed-off-by: Marcus Cooper <codekipper@gmail.com>
> >
> > I'd like to have Mark's input on this, but I'm really worried about
> > the interaction with the proper TDM support.
> >
> > Our fundamental issue is that the controller can have up to 8
> > channels, but either on 4 lines (instead of 1), or 8 channels on 1
> > (like proper TDM) (or any combination between the two, but that should
> > be pretty rare).
>
> I understand...maybe the TDM needs to be extended to support this to consider
> channel mapping and multiple transfer lines. I was thinking about the later when
> someone was requesting support on IIRC a while ago, I thought masking might
> of been a solution. These can wait as the only consumer at the moment is
> LibreELEC and we can patch it there.

Hi Marcus,

FWIW, the TI McASP driver has support for TDM & (i think?) multiple
transfer lines which are called serializers.
Maybe this can help with inspiration?
see https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/sound/soc/ti/davinci-mcasp.c
sample DTS:

&mcasp0 {
    #sound-dai-cells = <0>;
    status = "okay";
    pinctrl-names = "default";
    pinctrl-0 = <&mcasp0_pins>;

    op-mode = <0>;
    tdm-slots = <8>;
    serial-dir = <
        2 0 1 0
        0 0 0 0
        0 0 0 0
        0 0 0 0
    >;
    tx-num-evt = <1>;
    rx-num-evt = <1>;
};


Cheers!

> Do you have any ideas Master?
> CK
> >
> > You're trying to do the first one, and I'm trying to do the second one.
> >
> > There's a number of assumptions later on that will break the TDM case,
> > see below for examples
> >
> > > ---
> > >  sound/soc/sunxi/sun4i-i2s.c | 44 ++++++++++++++++++++++++++++++++-----
> > >  1 file changed, 39 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/sound/soc/sunxi/sun4i-i2s.c b/sound/soc/sunxi/sun4i-i2s.c
> > > index bca73b3c0d74..75217fb52bfa 100644
> > > --- a/sound/soc/sunxi/sun4i-i2s.c
> > > +++ b/sound/soc/sunxi/sun4i-i2s.c
> > > @@ -23,7 +23,7 @@
> > >
> > >  #define SUN4I_I2S_CTRL_REG           0x00
> > >  #define SUN4I_I2S_CTRL_SDO_EN_MASK           GENMASK(11, 8)
> > > -#define SUN4I_I2S_CTRL_SDO_EN(sdo)                   BIT(8 + (sdo))
> > > +#define SUN4I_I2S_CTRL_SDO_EN(lines)         (((1 << lines) - 1) << 8)
> > >  #define SUN4I_I2S_CTRL_MODE_MASK             BIT(5)
> > >  #define SUN4I_I2S_CTRL_MODE_SLAVE                    (1 << 5)
> > >  #define SUN4I_I2S_CTRL_MODE_MASTER                   (0 << 5)
> > > @@ -355,14 +355,23 @@ static int sun4i_i2s_hw_params(struct snd_pcm_substream *substream,
> > >       struct sun4i_i2s *i2s = snd_soc_dai_get_drvdata(dai);
> > >       int sr, wss, channels;
> > >       u32 width;
> > > +     int lines;
> > >
> > >       channels = params_channels(params);
> > > -     if (channels != 2) {
> > > +     if ((channels > dai->driver->playback.channels_max) ||
> > > +             (channels < dai->driver->playback.channels_min)) {
> > >               dev_err(dai->dev, "Unsupported number of channels: %d\n",
> > >                       channels);
> > >               return -EINVAL;
> > >       }
> > >
> > > +     lines = (channels + 1) / 2;
> > > +
> > > +     /* Enable the required output lines */
> > > +     regmap_update_bits(i2s->regmap, SUN4I_I2S_CTRL_REG,
> > > +                        SUN4I_I2S_CTRL_SDO_EN_MASK,
> > > +                        SUN4I_I2S_CTRL_SDO_EN(lines));
> > > +
> >
> > This has the assumption that each line will have 2 channels, which is wrong.
> >
> > >       if (i2s->variant->is_h3_i2s_based) {
> > >               regmap_update_bits(i2s->regmap, SUN8I_I2S_CHAN_CFG_REG,
> > >                                  SUN8I_I2S_CHAN_CFG_TX_SLOT_NUM_MASK,
> > > @@ -373,8 +382,19 @@ static int sun4i_i2s_hw_params(struct snd_pcm_substream *substream,
> > >       }
> > >
> > >       /* Map the channels for playback and capture */
> > > -     regmap_field_write(i2s->field_txchanmap, 0x76543210);
> > >       regmap_field_write(i2s->field_rxchanmap, 0x00003210);
> > > +     regmap_field_write(i2s->field_txchanmap, 0x10);
> > > +     if (i2s->variant->is_h3_i2s_based) {
> > > +             if (channels > 2)
> > > +                     regmap_write(i2s->regmap,
> > > +                                  SUN8I_I2S_TX_CHAN_MAP_REG+4, 0x32);
> > > +             if (channels > 4)
> > > +                     regmap_write(i2s->regmap,
> > > +                                  SUN8I_I2S_TX_CHAN_MAP_REG+8, 0x54);
> > > +             if (channels > 6)
> > > +                     regmap_write(i2s->regmap,
> > > +                                  SUN8I_I2S_TX_CHAN_MAP_REG+12, 0x76);
> > > +     }
> >
> > And this creates a mapping matching that.
> >
> > >       /* Configure the channels */
> > >       regmap_field_write(i2s->field_txchansel,
> > > @@ -1057,9 +1077,10 @@ static int sun4i_i2s_init_regmap_fields(struct device *dev,
> > >  static int sun4i_i2s_probe(struct platform_device *pdev)
> > >  {
> > >       struct sun4i_i2s *i2s;
> > > +     struct snd_soc_dai_driver *soc_dai;
> > >       struct resource *res;
> > >       void __iomem *regs;
> > > -     int irq, ret;
> > > +     int irq, ret, val;
> > >
> > >       i2s = devm_kzalloc(&pdev->dev, sizeof(*i2s), GFP_KERNEL);
> > >       if (!i2s)
> > > @@ -1126,6 +1147,19 @@ static int sun4i_i2s_probe(struct platform_device *pdev)
> > >       i2s->capture_dma_data.addr = res->start + SUN4I_I2S_FIFO_RX_REG;
> > >       i2s->capture_dma_data.maxburst = 8;
> > >
> > > +     soc_dai = devm_kmemdup(&pdev->dev, &sun4i_i2s_dai,
> > > +                            sizeof(*soc_dai), GFP_KERNEL);
> > > +     if (!soc_dai) {
> > > +             ret = -ENOMEM;
> > > +             goto err_pm_disable;
> > > +     }
> > > +
> > > +     if (!of_property_read_u32(pdev->dev.of_node,
> > > +                               "allwinner,playback-channels", &val)) {
> > > +             if (val >= 2 && val <= 8)
> > > +                     soc_dai->playback.channels_max = val;
> > > +     }
> > > +
> >
> > I'm not quite sure how this works.
> >
> > of_property_read_u32 will return 0, so you will enter in the
> > condition. But what happens if the property is missing?
> >
> > Maxime
> >
> > --
> > Maxime Ripard, Bootlin
> > Embedded Linux and Kernel engineering
> > https://bootlin.com
>
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