[alsa-devel] [PATCH] ASoC: rt5677: make volume TLV closer to reality

[Dylan Reid]

On Thu, Oct 9, 2014 at 2:51 PM, Takashi Iwai <tiwai at suse.de> wrote:
> At Thu,  9 Oct 2014 14:00:09 -0700,
> Dylan Reid wrote:
>>
>> The volume blocks have an step of 0.375dB, but TLV uses 0.01dB for
>> units.  Approximate 0.375 as 0.37.  It leaves the minimum value off by
>> 1.15dB, but that is better than being off by ~500 as it was with 37.5
>> as the step.
>>
>> Signed-off-by: Dylan Reid <dgreid at chromium.org>
>> ---
>> Just a suggestion.  It seems to me to be the lesser of two evils.
>> This probably won't be the last codec that has a higher resolution
>> than 0.01dB, should we come up with a way to express that?
>
> How about using TLV_DB_MINMAX instead?

That sounds like the right idea.  It'll only be off by 0.005dB.  I'll
replace this change with that one.

Thanks!

-dg

>
>
> Takashi
>
>> ---
>>  sound/soc/codecs/rt5677.c | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/sound/soc/codecs/rt5677.c b/sound/soc/codecs/rt5677.c
>> index 16aa4d9..f139d5a 100644
>> --- a/sound/soc/codecs/rt5677.c
>> +++ b/sound/soc/codecs/rt5677.c
>> @@ -538,9 +538,11 @@ static bool rt5677_readable_register(struct device *dev, unsigned int reg)
>>  }
>>
>>  static const DECLARE_TLV_DB_SCALE(out_vol_tlv, -4650, 150, 0);
>> -static const DECLARE_TLV_DB_SCALE(dac_vol_tlv, -65625, 375, 0);
>> +/* Actual min=-65.625dB and step=0.375dB but only have 0.01 resolution. */
>> +static const DECLARE_TLV_DB_SCALE(dac_vol_tlv, -6475, 37, 0);
>>  static const DECLARE_TLV_DB_SCALE(in_vol_tlv, -3450, 150, 0);
>> -static const DECLARE_TLV_DB_SCALE(adc_vol_tlv, -17625, 375, 0);
>> +/* Actual min=-17.625dB and step=0.375dB but only have 0.01 resolution. */
>> +static const DECLARE_TLV_DB_SCALE(adc_vol_tlv, -1739, 37, 0);
>>  static const DECLARE_TLV_DB_SCALE(adc_bst_tlv, 0, 1200, 0);
>>  static const DECLARE_TLV_DB_SCALE(st_vol_tlv, -4650, 150, 0);
>>
>> --
>> 2.1.2.330.g565301e
>>