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    Subject[PATCH AUTOSEL 4.14 02/20] ASoC: ssm2602: Add workaround for playback distortions
    Date
    From: Paweł Anikiel <pan@semihalf.com>

    [ Upstream commit f63550e2b165208a2f382afcaf5551df9569e1d4 ]

    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
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    sound/soc/codecs/ssm2602.c | 15 +++++++++++++++
    1 file changed, 15 insertions(+)

    diff --git a/sound/soc/codecs/ssm2602.c b/sound/soc/codecs/ssm2602.c
    index 5e80867d09ef7..256e5af6690b7 100644
    --- a/sound/soc/codecs/ssm2602.c
    +++ b/sound/soc/codecs/ssm2602.c
    @@ -67,6 +67,18 @@ static const struct reg_default ssm2602_reg[SSM2602_CACHEREGNUM] = {
    { .reg = 0x09, .def = 0x0000 }
    };

    +/*
    + * ssm2602 register patch
    + * Workaround for playback distortions after power up: activates digital
    + * core, and then powers on output, DAC, and whole chip at the same time
    + */
    +
    +static const struct reg_sequence ssm2602_patch[] = {
    + { SSM2602_ACTIVE, 0x01 },
    + { SSM2602_PWR, 0x07 },
    + { SSM2602_RESET, 0x00 },
    +};
    +

    /*Appending several "None"s just for OSS mixer use*/
    static const char *ssm2602_input_select[] = {
    @@ -577,6 +589,9 @@ static int ssm260x_codec_probe(struct snd_soc_codec *codec)
    return ret;
    }

    + regmap_register_patch(ssm2602->regmap, ssm2602_patch,
    + ARRAY_SIZE(ssm2602_patch));
    +
    /* set the update bits */
    regmap_update_bits(ssm2602->regmap, SSM2602_LINVOL,
    LINVOL_LRIN_BOTH, LINVOL_LRIN_BOTH);
    --
    2.39.2
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