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Subject: Re: [PATCH v6 02/14] ASoC: sun4i-i2s: Change set_chan_cfg() params
To:     Maxime Ripard <maxime@cerno.tech>,
        =?UTF-8?B?Q2zDqW1lbnQgUMOpcm9u?= <peron.clem@gmail.com>
Cc:     Chen-Yu Tsai <wens@csie.org>, Rob Herring <robh+dt@kernel.org>,
        Mark Brown <broonie@kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>,
        Marcus Cooper <codekipper@gmail.com>,
        Jernej Skrabec <jernej.skrabec@siol.net>,
        Linux-ALSA <alsa-devel@alsa-project.org>,
        devicetree <devicetree@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-sunxi <linux-sunxi@googlegroups.com>
References: <20201003141950.455829-1-peron.clem@gmail.com>
 <20201003141950.455829-3-peron.clem@gmail.com>
 <20201005121307.v6jpyeyfi4kxc2cl@gilmour.lan>
 <CAJiuCcdd6_kzsxEERZbj2Budjmuyv6gV_sPG8LjLY=fk+MO8zQ@mail.gmail.com>
 <20201012121536.z5d7kecdxaabw35n@gilmour.lan>
From:   Samuel Holland <samuel@sholland.org>
Message-ID: <0d6f0693-5ca9-9b48-4d33-a969bd5b1b1b@sholland.org>
Date:   Mon, 12 Oct 2020 20:15:30 -0500
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On 10/12/20 7:15 AM, Maxime Ripard wrote:
> Hi,
> 
> On Mon, Oct 05, 2020 at 03:23:12PM +0200, Cl?ment P?ron wrote:
>> On Mon, 5 Oct 2020 at 14:13, Maxime Ripard <maxime@cerno.tech> wrote:
>>>
>>> On Sat, Oct 03, 2020 at 04:19:38PM +0200, Cl?ment P?ron wrote:
>>>> As slots and slot_width can be set manually using set_tdm().
>>>> These values are then kept in sun4i_i2s struct.
>>>> So we need to check if these values are setted or not
>>>> in the struct.
>>>>
>>>> Avoid to check for this logic in set_chan_cfg(). This will
>>>> duplicate the same check instead pass the required values
>>>> as params to set_chan_cfg().
>>>>
>>>> This will also avoid a bug when we will enable 20/24bits support,
>>>> i2s->slot_width is not actually used in the lrck_period computation.
>>>>
>>>> Suggested-by: Samuel Holland <samuel@sholland.org>
>>>> Signed-off-by: Cl?ment P?ron <peron.clem@gmail.com>
>>>> ---
>>>>  sound/soc/sunxi/sun4i-i2s.c | 36 ++++++++++++++----------------------
>>>>  1 file changed, 14 insertions(+), 22 deletions(-)
>>>>
>>>> diff --git a/sound/soc/sunxi/sun4i-i2s.c b/sound/soc/sunxi/sun4i-i2s.c
>>>> index c5ccd423e6d3..1f577dbc20a6 100644
>>>> --- a/sound/soc/sunxi/sun4i-i2s.c
>>>> +++ b/sound/soc/sunxi/sun4i-i2s.c
>>>> @@ -177,8 +177,9 @@ struct sun4i_i2s_quirks {
>>>>       unsigned long (*get_bclk_parent_rate)(const struct sun4i_i2s *);
>>>>       s8      (*get_sr)(const struct sun4i_i2s *, int);
>>>>       s8      (*get_wss)(const struct sun4i_i2s *, int);
>>>> -     int     (*set_chan_cfg)(const struct sun4i_i2s *,
>>>> -                             const struct snd_pcm_hw_params *);
>>>> +     int     (*set_chan_cfg)(const struct sun4i_i2s *i2s,
>>>> +                             unsigned int channels,  unsigned int slots,
>>>> +                             unsigned int slot_width);
>>>>       int     (*set_fmt)(const struct sun4i_i2s *, unsigned int);
>>>>  };
>>>>
>>>> @@ -414,10 +415,9 @@ static s8 sun8i_i2s_get_sr_wss(const struct sun4i_i2s *i2s, int width)
>>>>  }
>>>>
>>>>  static int sun4i_i2s_set_chan_cfg(const struct sun4i_i2s *i2s,
>>>> -                               const struct snd_pcm_hw_params *params)
>>>> +                               unsigned int channels, unsigned int slots,
>>>> +                               unsigned int slot_width)
>>>>  {
>>>> -     unsigned int channels = params_channels(params);
>>>> -
>>>>       /* Map the channels for playback and capture */
>>>>       regmap_write(i2s->regmap, SUN4I_I2S_TX_CHAN_MAP_REG, 0x76543210);
>>>>       regmap_write(i2s->regmap, SUN4I_I2S_RX_CHAN_MAP_REG, 0x00003210);
>>>> @@ -434,15 +434,11 @@ static int sun4i_i2s_set_chan_cfg(const struct sun4i_i2s *i2s,
>>>>  }
>>>>
>>>>  static int sun8i_i2s_set_chan_cfg(const struct sun4i_i2s *i2s,
>>>> -                               const struct snd_pcm_hw_params *params)
>>>> +                               unsigned int channels, unsigned int slots,
>>>> +                               unsigned int slot_width)
>>>>  {
>>>> -     unsigned int channels = params_channels(params);
>>>> -     unsigned int slots = channels;
>>>>       unsigned int lrck_period;
>>>>
>>>> -     if (i2s->slots)
>>>> -             slots = i2s->slots;
>>>> -
>>>>       /* Map the channels for playback and capture */
>>>>       regmap_write(i2s->regmap, SUN8I_I2S_TX_CHAN_MAP_REG, 0x76543210);
>>>>       regmap_write(i2s->regmap, SUN8I_I2S_RX_CHAN_MAP_REG, 0x76543210);
>>>> @@ -467,11 +463,11 @@ static int sun8i_i2s_set_chan_cfg(const struct sun4i_i2s *i2s,
>>>>       case SND_SOC_DAIFMT_DSP_B:
>>>>       case SND_SOC_DAIFMT_LEFT_J:
>>>>       case SND_SOC_DAIFMT_RIGHT_J:
>>>> -             lrck_period = params_physical_width(params) * slots;
>>>> +             lrck_period = slot_width * slots;
>>>>               break;
>>>>
>>>>       case SND_SOC_DAIFMT_I2S:
>>>> -             lrck_period = params_physical_width(params);
>>>> +             lrck_period = slot_width;
>>>>               break;
>>>>
>>>>       default:
>>>> @@ -490,15 +486,11 @@ static int sun8i_i2s_set_chan_cfg(const struct sun4i_i2s *i2s,
>>>>  }
>>>>
>>>>  static int sun50i_h6_i2s_set_chan_cfg(const struct sun4i_i2s *i2s,
>>>> -                                   const struct snd_pcm_hw_params *params)
>>>> +                                   unsigned int channels, unsigned int slots,
>>>> +                                   unsigned int slot_width)
>>>>  {
>>>> -     unsigned int channels = params_channels(params);
>>>> -     unsigned int slots = channels;
>>>>       unsigned int lrck_period;
>>>>
>>>> -     if (i2s->slots)
>>>> -             slots = i2s->slots;
>>>> -
>>>>       /* Map the channels for playback and capture */
>>>>       regmap_write(i2s->regmap, SUN50I_H6_I2S_TX_CHAN_MAP0_REG, 0xFEDCBA98);
>>>>       regmap_write(i2s->regmap, SUN50I_H6_I2S_TX_CHAN_MAP1_REG, 0x76543210);
>>>> @@ -525,11 +517,11 @@ static int sun50i_h6_i2s_set_chan_cfg(const struct sun4i_i2s *i2s,
>>>>       case SND_SOC_DAIFMT_DSP_B:
>>>>       case SND_SOC_DAIFMT_LEFT_J:
>>>>       case SND_SOC_DAIFMT_RIGHT_J:
>>>> -             lrck_period = params_physical_width(params) * slots;
>>>> +             lrck_period = slot_width * slots;
>>>>               break;
>>>>
>>>>       case SND_SOC_DAIFMT_I2S:
>>>> -             lrck_period = params_physical_width(params);
>>>> +             lrck_period = slot_width;
>>>>               break;
>>>>
>>>>       default:
>>>> @@ -565,7 +557,7 @@ static int sun4i_i2s_hw_params(struct snd_pcm_substream *substream,
>>>>       if (i2s->slot_width)
>>>>               slot_width = i2s->slot_width;
>>>>
>>>> -     ret = i2s->variant->set_chan_cfg(i2s, params);
>>>> +     ret = i2s->variant->set_chan_cfg(i2s, channels, slots, slot_width);
>>>
>>> Isn't slots and slot_width set to 0 here ?
>>
>> No, there is still a check before calling the set_cfg function.
>>
>>   unsigned int slot_width = params_physical_width(params);
>>   unsigned int channels = params_channels(params);
>>   unsigned int slots = channels;
>>
>>   if (i2s->slots)
>>   slots = i2s->slots;
>>
>>   if (i2s->slot_width)
>>   slot_width = i2s->slot_width;
>>
>> ret = i2s->variant->set_chan_cfg(i2s, channels, slots, slot_width);
>>
>> So slot_width will be equal to params_physical_width(params);
>> like before
> 
> Still, it's not obvious what slots and slot_width are going to be set to
> in a non-TDM setup where that doesn't really make much sense.

My understanding is:

"slots" is channels per frame + padding slots, regardless of format.
"slot_width" is bits per sample + padding bits, regardless of format.

Some formats may require or prohibit certain padding, but that has no
effect on the definitions.

That seems clear to me? At least that's what I implemented (and you
acked) in sun8i-codec.

> I assume you want to reduce the boilerplate, then we can make an helper
> to get the frame size and the number of channels / slots if needed

What would you name the return values, if not "slots" and "slot_width"?
"channels" and "word_size" would be inaccurate, because those terms
refer to the values without padding.

> Maxime

Cheers,
Samuel