On Mon, Aug 26, 2019 at 1:38 AM Hans de Goede hdegoede@redhat.com 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?
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 – -12dB 0001 – -10.5dB 0010 – -9dB 0011 – -7.5dB 0100 – -6dB 1000 – -4.5dB 1001 – -3dB 1010 – -1.5dB 1011 – 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?
Thanks Daniel