Re: [alsa-devel] [PATCH 4/4] sound: codecs: pcm1792a: introduce channel side

From: "Raphaël Poggi" <poggi.raph@gmail.com>
To: Michael Trimarchi <michael@amarulasolutions.com>
Cc: perex@perex.cz, tiwai@suse.com,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [alsa-devel] [PATCH 4/4] sound: codecs: pcm1792a: introduce channel side
Date: Tue, 24 Nov 2015 17:04:58 +0100	[thread overview]
Message-ID: <CACqcpZDQRtSqmLDC65ajNGY=VU8TFZBnVxhaM+cES37rv7zmyg@mail.gmail.com> (raw)
In-Reply-To: <CAOf5uwmdwcdbxx2b6DvMeOJBahkZ3iiosWtHPD2zhxcDqO2b_A@mail.gmail.com>

Hi,

2015-11-24 9:27 GMT+01:00 Michael Trimarchi <michael@amarulasolutions.com>:
> Hi
>
> On Tue, Nov 24, 2015 at 9:21 AM, Raphaël Poggi <poggi.raph@gmail.com> wrote:
>> Hi,
>>
>> 2015-11-21 10:37 GMT+01:00 Michael Trimarchi <michael@amarulasolutions.com>:
>>> Hi
>>>
>>> On Fri, Nov 20, 2015 at 11:09 AM, Raphael Poggi <poggi.raph@gmail.com> wrote:
>>>> From: Raphael Poggi <poggi.raph@gmail.com>
>>>>
>>>> Add possibility to choose the channel side using the device tree,
>>>> and also modify it using alsa ctrl.
>>>>
>>>> Signed-off-by: Raphael Poggi <poggi.raph@gmail.com>
>>>> ---
>>>>  sound/soc/codecs/pcm1792a.c | 46 +++++++++++++++++++++++++++++++++++++++++++++
>>>>  1 file changed, 46 insertions(+)
>>>>
>>>> diff --git a/sound/soc/codecs/pcm1792a.c b/sound/soc/codecs/pcm1792a.c
>>>> index febaa48..005b679 100644
>>>> --- a/sound/soc/codecs/pcm1792a.c
>>>> +++ b/sound/soc/codecs/pcm1792a.c
>>>> @@ -65,6 +65,12 @@ static const struct reg_default pcm1792a_reg_defaults[] = {
>>>>         { PCM1792A_DEVICE_ID, 0x00 },
>>>>  };
>>>>
>>>> +enum __pcm1792_side {
>>>> +       STEREO,
>>>> +       MONORAL_LEFT,
>>>> +       MONORAL_RIGHT
>>>> +};
>>>> +
>>>>  static bool pcm1792a_accessible_reg(struct device *dev, unsigned int reg)
>>>>  {
>>>>         return reg >= 0x10 && reg <= 0x17;
>>>> @@ -83,6 +89,7 @@ struct pcm1792a_private {
>>>>         struct regmap *regmap;
>>>>         unsigned int format;
>>>>         unsigned int rate;
>>>> +       unsigned int side;
>>>>  };
>>>>
>>>>  static int pcm1792a_set_dai_fmt(struct snd_soc_dai *codec_dai,
>>>> @@ -153,6 +160,13 @@ static int pcm1792a_hw_params(struct snd_pcm_substream *substream,
>>>>         ret = regmap_update_bits(priv->regmap, PCM1792A_FMT_CONTROL,
>>>>                                  PCM1792A_FMT_MASK | PCM1792A_ATLD_ENABLE, val);
>>>>
>>>> +       if (priv->side == MONORAL_LEFT)
>>>> +               val = PCM1792A_CHANNEL_MONO_LEFT;
>>>> +       else if (priv->side == MONORAL_RIGHT)
>>>> +               val = PCM1792A_CHANNEL_MONO_RIGHT;
>>>> +
>>>> +       regmap_update_bits(priv->regmap, PCM1792A_CHANNEL, PCM1792A_CHANNEL_MONO_MASK, val);
>>>> +
>>>>         return ret;
>>>>  }
>>>>
>>>> @@ -222,10 +236,31 @@ static struct snd_soc_codec_driver soc_codec_dev_pcm1792a = {
>>>>         .num_dapm_routes        = ARRAY_SIZE(pcm1792a_dapm_routes),
>>>>  };
>>>>
>>>> +static int pcm1792a_of_init(struct spi_device *spi)
>>>> +{
>>>> +       int ret = 0;
>>>> +       struct pcm1792a_private *pcm1792a = dev_get_drvdata(&spi->dev);
>>>> +       const char *name;
>>>> +       struct device_node *np = spi->dev.of_node;
>>>> +
>>>> +       name = of_get_property(np, "ti,side", NULL);
>>>> +       if (name) {
>>>> +               if (!strcmp(name, "left"))
>>>> +                       pcm1792a->side = MONORAL_LEFT;
>>>> +               else
>>>> +                       pcm1792a->side = MONORAL_RIGHT;
>>>> +       }
>>>> +       else
>>>> +               pcm1792a->side = STEREO;
>>>> +
>>>> +       return ret;
>>>> +}
>>>> +
>>>>  static int pcm1792a_spi_probe(struct spi_device *spi)
>>>>  {
>>>>         struct pcm1792a_private *pcm1792a;
>>>>         int ret;
>>>> +       struct device_node *np = spi->dev.of_node;
>>>>
>>>>         pcm1792a = devm_kzalloc(&spi->dev, sizeof(struct pcm1792a_private),
>>>>                                 GFP_KERNEL);
>>>> @@ -241,6 +276,17 @@ static int pcm1792a_spi_probe(struct spi_device *spi)
>>>>                 return ret;
>>>>         }
>>>>
>>>> +       if (np) {
>>>> +               ret = pcm1792a_of_init(spi);
>>>> +               if (ret)
>>>> +                       return ret;
>>>> +       }
>>>> +
>>>> +       if (pcm1792a->side == MONORAL_LEFT)
>>>> +               regmap_update_bits(pcm1792a->regmap, PCM1792A_CHANNEL, PCM1792A_CHANNEL_MONO_MASK, PCM1792A_CHANNEL_MONO_LEFT);
>>>> +       else if (pcm1792a->side == MONORAL_RIGHT)
>>>> +               regmap_update_bits(pcm1792a->regmap, PCM1792A_CHANNEL, PCM1792A_CHANNEL_MONO_MASK, PCM1792A_CHANNEL_MONO_RIGHT);
>>>> +
>>>
>>> Why this is a part of dts and not a part of mixer control?
>>>
>>> Michael
>>>
>>
>> The "channel side" bindings should be used when the pcm7192a is used
>> in monaural mode (which requires two DACs, both DACs operate in a
>> balanced mode for one channel of audio input data).
>> This is a hardware level design, it will never change at runtime.
>> I feel that a device tree binding is more appropriate than a control.
>>
>
> Well I know exactly why is used for, but I don't really know if it's
> somenthing that should be
> in dts. Do I want to do channel inversion?
>
> Michael
>

I am not sure to understand. You mean "What if I want to do channel
inversion", right ?
If so, we have two differents "problems", one at hardware level design
because monaural mode requires two DACs, and an another one at
software level
"channel inversion".
I have always thought that hardware description should be in dts,
that's why I implement monaural mode using dts.

Honestly, I don't know what is the best solution between "this is a
hardware design, it should be in dts and shouldn't change" vs "this
should be an alsa controler because we want extra features independent
from hardware design"

Raphaël

>>>>         return snd_soc_register_codec(&spi->dev,
>>>>                         &soc_codec_dev_pcm1792a, &pcm1792a_dai, 1);
>>>>  }
>>>> --
>>>> 2.1.0
>>>>
>>>> _______________________________________________
>>>> Alsa-devel mailing list
>>>> Alsa-devel@alsa-project.org
>>>> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
>>>
>>>
>>>
>>> --
>>> | Michael Nazzareno Trimarchi                     Amarula Solutions BV |
>>> | COO  -  Founder                                      Cruquiuskade 47 |
>>> | +31(0)851119172                                 Amsterdam 1018 AM NL |
>>> |                  [`as] http://www.amarulasolutions.com               |
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>> Please read the FAQ at  http://www.tux.org/lkml/
>
>
>
> --
> | Michael Nazzareno Trimarchi                     Amarula Solutions BV |
> | COO  -  Founder                                      Cruquiuskade 47 |
> | +31(0)851119172                                 Amsterdam 1018 AM NL |
> |                  [`as] http://www.amarulasolutions.com               |
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/