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    Subject[PATCH 4.2.y-ckt 172/218] ASoC: ssm4567: Reset device before regcache_sync()
    Date
    4.2.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

    ---8<------------------------------------------------------------

    From: Lars-Peter Clausen <lars@metafoo.de>

    commit 712a8038cc24dba668afe82f0413714ca87184e0 upstream.

    When the ssm4567 is powered up the driver calles regcache_sync() to restore
    the register map content. regcache_sync() assumes that the device is in its
    power-on reset state. Make sure that this is the case by explicitly
    resetting the ssm4567 register map before calling regcache_sync() otherwise
    we might end up with a incorrect register map which leads to undefined
    behaviour.

    One such undefined behaviour was observed when returning from system
    suspend while a playback stream is active, in that case the ssm4567 was
    kept muted after resume.

    Fixes: 1ee44ce03011 ("ASoC: ssm4567: Add driver for Analog Devices SSM4567 amplifier")
    Reported-by: Harsha Priya <harshapriya.n@intel.com>
    Tested-by: Fang, Yang A <yang.a.fang@intel.com>
    Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
    Signed-off-by: Mark Brown <broonie@kernel.org>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    sound/soc/codecs/ssm4567.c | 5 +++++
    1 file changed, 5 insertions(+)

    diff --git a/sound/soc/codecs/ssm4567.c b/sound/soc/codecs/ssm4567.c
    index 84a4f5a..0bfc28b 100644
    --- a/sound/soc/codecs/ssm4567.c
    +++ b/sound/soc/codecs/ssm4567.c
    @@ -338,6 +338,11 @@ static int ssm4567_set_power(struct ssm4567 *ssm4567, bool enable)
    regcache_cache_only(ssm4567->regmap, !enable);

    if (enable) {
    + ret = regmap_write(ssm4567->regmap, SSM4567_REG_SOFT_RESET,
    + 0x00);
    + if (ret)
    + return ret;
    +
    ret = regmap_update_bits(ssm4567->regmap,
    SSM4567_REG_POWER_CTRL,
    SSM4567_POWER_SPWDN, 0x00);
    --
    2.7.4
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