Re: [PATCH] ASoC: es8316: limit headphone mixer volume

[Hans de Goede]

Hi,

On 26-08-19 04:53, Daniel Drake wrote:
> On Mon, Aug 26, 2019 at 1:38 AM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> > On 24-08-19 23:04, Katsuhiro Suzuki wrote:
> > > This patch limits Headphone mixer volume to 4 from 7.
> > > Because output sound suddenly becomes very loudly with many noise if
> > > set volume over 4.
>
> That sounds like something that should be limited in UCM.
>
> > Higher then 4 not working matches my experience, see this comment from
> > the UCM file: alsa-lib/src/conf/ucm/codecs/es8316/EnableSeq.conf :
> >
> > # Set HP mixer vol to -6 dB (4/7) louder does not work
> > cset "name='Headphone Mixer Volume' 4"
>
> What does "does not work" mean more precisely?

IIRC garbled sound.

> I checked the spec, there is indeed something wrong in the kernel driver here.
> The db scale is not a simple scale as the kernel source suggests.
>
> Instead it is:
> 0000 â -12dB
> 0001 â -10.5dB
> 0010 â -9dB
> 0011 â -7.5dB
> 0100 â -6dB
> 1000 â -4.5dB
> 1001 â -3dB
> 1010 â -1.5dB
> 1011 â 0dB
>
> So perhaps we can fix the kernel to follow this table and then use UCM
> to limit the volume if its too high on a given platform?

Yes that sounds like the right thing to do. Katsuhiro can you confirm that
using this table allows using the full scale ? note that the full scale now
has 9 steps rather then 8.

Regards,

Hans