Haidar Lee <haidar.lee@adlinktech.com> says:
The 'Digital Volume Control' added in v5.7 has never worked correctly:
the driver writes the 32-bit DVC coefficient LSB first, but the device
latches the whole coefficient on the write to the last byte (DVC_CFG4),
so every volume change applies a mix of the previous coefficient's
upper bytes and the new LSB. Depending on the sequence of values this
mutes the output entirely or plays at full volume regardless of the
requested level.
Debugged on a TAS2562 (ADLINK OSM-520 / MT8189): traced the I2C writes
with ftrace to confirm the driver writes the intended bytes, then
reproduced both behaviours by writing the same coefficients manually in
each byte order. Patch 1 fixes the write order; patch 2 fixes two wrong
entries in the volume lookup table found while debugging this.
Link: https://patch.msgid.link/20260715-tas2562-dvc-fix-v1-0-072b13901b20@adlinktech.com