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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>,
        alsa-devel@alsa-project.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-sunxi@googlegroups.com
References: <20201003141950.455829-1-peron.clem@gmail.com>
 <20201003141950.455829-3-peron.clem@gmail.com>
 <20201005121307.v6jpyeyfi4kxc2cl@gilmour.lan>
From:   Samuel Holland <samuel@sholland.org>
Message-ID: <fae04296-9865-3dcb-e02d-46062bf778a8@sholland.org>
Date:   Tue, 6 Oct 2020 00:03:14 -0500
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On 10/5/20 7:13 AM, Maxime Ripard 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 ?
> 
> And therefore, wouldn't we set lrck_period to 0 if we're using any
> format but I2S?
> 
> More importantly, I'm not really convinced this needs to be done, and it
> introduces some side effects that are not explained.

If I set dai-tdm-slot-width = <32> and start a stream using S16_LE,
currently we would calculate BCLK for 32-bit slots, but program
lrck_period for 16-bit slots, making the sample rate double what we
expected. That sounds like a bug to me. (Because of that, as Chen-Yu
mentioned in reply to v5, this should be the first patch in the series.)

Could you be more specific what side effects you are referring to?

> Maxime

Cheers,
Samuel