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

[Takashi Iwai]

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?


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
>