ASoC: fsl_ssi: serialize AC'97 register access operations

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AC'97 register access operations (both read and write) on SSI use a one,
shared set of SSI registers for AC'97 register address and data.
This means that only one such access is possible at a time and so all these
operations need to be serialized.

Since an AC'97 register access operation in this driver takes 100us+ let's
use a mutex for this.

Use this opportunity to also change a default value returned from AC'97
register read function from -1 to 0, since that's what AC'97 specs require
to be returned when unknown / undefined registers are read.

Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Mark Brown <broonie@kernel.org>

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Maciej S. Szmigiero 2017-11-20 23:16:07 +01:00 • committed by Mark Brown

parent 695b78b548

commit b880b8056b

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sound/soc/fsl/fsl_ssi.c

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