Re: [PATCH 1/3] ASoC: es8316: Increment max value for ALC Capture Target Volume control

[Cristian Ciocaltea <cristian.ciocaltea@collabora.com>]

On 5/24/23 13:30, Mark Brown wrote:
> On Wed, May 24, 2023 at 10:41:54AM +0300, Cristian Ciocaltea wrote:
> 
>> This means that either the hardware default is wrongly set to 0xB
>> instead of 0xA, or the specs are incorrect and instead of having the
>> range 0xA-0xF mapped to -1.5 dB, the single value 0xA should have been
>> mapped to -1.5 dB and the remaining range 0xB-0xF to 0 dB.
> 
>> Increment the max value allowed for ALC Capture Target Volume control,
>> so that it matches the hardware default.
> 
>> -	SOC_SINGLE_TLV("ALC Capture Target Volume", ES8316_ADC_ALC3, 4, 10, 0,
>> +	SOC_SINGLE_TLV("ALC Capture Target Volume", ES8316_ADC_ALC3, 4, 11, 0,
>>  		       alc_target_tlv),
> 
> The description above of what the control does doesn't seem to match
> what alc_target_tlv specifies - it is:
> 
>   static const SNDRV_CTL_TLVD_DECLARE_DB_SCALE(alc_target_tlv, -1650, 150, 0);
> 
> which is saying that the value goes from -16.5dB up in steps of 1.5dB
> but your description above says that 0-10 map to -1.5dB and other values
> are 0dB.

My description above mentioned only the 0xA-0xF (10-15) range, anything
before that is fine and the implementation matches the specs:

0000 –> -16.5 dB
0001 –> -15.0 dB
0010 –> -13.5 dB
...
0111 –>  -6.0 dB
1000 –>  -4.5 dB
1001 –>  -3.0 dB

The inconsistency is here:
1010-1111 –> -1.5 dB

Since the hardware default is 1011 (11) instead of 1010 (10), I assumed
the specs could be wrong and probably should have provided the following
mappings:

1010 ->  -1.5 dB
1011-1111 -> 0 dB

> Presumably you can check the effects of changing the value?  It seems
> plausible that what's written in the code might be accurate and the
> higher values might actually change the gain but it'd be better to
> check.

I haven't noticed a (measurable) change in gain when switching between
10 and 11, but my testing equipment is also not that great. Will try to
improve the tests accuracy.

Thanks,
Cristian