• Paweł Anikiel's avatar
    ASoC: ssm2602: Add workaround for playback distortions · f63550e2
    Paweł Anikiel authored
    Apply a workaround for what appears to be a hardware quirk.
    
    The problem seems to happen when enabling "whole chip power" (bit D7
    register R6) for the very first time after the chip receives power. If
    either "output" (D4) or "DAC" (D3) aren't powered on at that time,
    playback becomes very distorted later on.
    
    This happens on the Google Chameleon v3, as well as on a ZYBO Z7-10:
    https://ez.analog.com/audio/f/q-a/543726/solved-ssm2603-right-output-offset-issue/480229
    I suspect this happens only when using an external MCLK signal (which
    is the case for both of these boards).
    
    Here are some experiments run on a Google Chameleon v3. These were run
    in userspace using a wrapper around the i2cset utility:
    ssmset() {
            i2cset -y 0 0x1a $(($1*2)) $2
    }
    
    For each of the following sequences, we apply power to the ssm2603
    chip, set the configuration registers R0-R5 and R7-R8, run the selected
    sequence, and check for distortions on playback.
    
      ssmset 0x09 0x01 # core
      ssmset 0x06 0x07 # chip, out, dac
      OK
    
      ssmset 0x09 0x01 # core
      ssmset 0x06 0x87 # out, dac
      ssmset 0x06 0x07 # chip
      OK
    
      (disable MCLK)
      ssmset 0x09 0x01 # core
      ssmset 0x06 0x1f # chip
      ssmset 0x06 0x07 # out, dac
      (enable MCLK)
      OK
    
      ssmset 0x09 0x01 # core
      ssmset 0x06 0x1f # chip
      ssmset 0x06 0x07 # out, dac
      NOT OK
    
      ssmset 0x06 0x1f # chip
      ssmset 0x09 0x01 # core
      ssmset 0x06 0x07 # out, dac
      NOT OK
    
      ssmset 0x09 0x01 # core
      ssmset 0x06 0x0f # chip, out
      ssmset 0x06 0x07 # dac
      NOT OK
    
      ssmset 0x09 0x01 # core
      ssmset 0x06 0x17 # chip, dac
      ssmset 0x06 0x07 # out
      NOT OK
    
    For each of the following sequences, we apply power to the ssm2603
    chip, run the selected sequence, issue a reset with R15, configure
    R0-R5 and R7-R8, run one of the NOT OK sequences from above, and check
    for distortions.
    
      ssmset 0x09 0x01 # core
      ssmset 0x06 0x07 # chip, out, dac
      OK
    
      (disable MCLK)
      ssmset 0x09 0x01 # core
      ssmset 0x06 0x07 # chip, out, dac
      (enable MCLK after reset)
      NOT OK
    
      ssmset 0x09 0x01 # core
      ssmset 0x06 0x17 # chip, dac
      NOT OK
    
      ssmset 0x09 0x01 # core
      ssmset 0x06 0x0f # chip, out
      NOT OK
    
      ssmset 0x06 0x07 # chip, out, dac
      NOT OK
    
    Signed-off-by: Paweł Anikiel <pan@semihalf.com
    Link: https://lore.kernel.org/r/20230508113037.137627-8-pan@semihalf.com
    Signed-off-by: Mark Brown <broonie@kernel.org
    f63550e2
ssm2602.c 18.6 KB