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

From: Katsuhiro Suzuki
Date: Mon Aug 26 2019 - 11:25:31 EST

Hello Hans, Daniel,

Thank you for reviewing and comment.

On 2019/08/26 18:09, Hans de Goede wrote:

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.

I've finished testing this table on my board (RockPro64).
Every values work well without garbled sound.

I checked address 0x16 register via /sys/kernel/debug/regmap too.
The register values and dB (get from alsamixer) are the following if
I increase headphone volume to max from min.

reg dB
0x16 scale
0x00 -12.00
0x11 -10.50
0x22 -9.00
0x33 -7.50
0x44 -6.00
0x88 -4.50
0x99 -3.00
0xaa -1.50
0xbb 0.00

And I found other problem, current code is inverted L/R volume.
It's only in Headphone "mixer" volume. It seems Headphone "master"
volume works correctly.

I'll fix these problems and send V2 patch set.



Best Regards,
Katsuhiro Suzuki