[PATCH 2/2] MFD: mc13xxx workaround SPI hardware bug on i.Mx

[broonie@opensource.wolfsonmicro.com (Mark Brown)]

On Tue, May 29, 2012 at 11:06:29AM +0200, Philippe R?tornaz wrote:
> The MC13xxx PMIC is mainly used on i.Mx SoC. On thoses SoC the SPI
> hardware will deassert CS line as soon as the SPI FIFO is empty.
> The MC13xxx hardware is very sensitive to CS line change as it
> corrupts the transfert if CS is deasserted in the middle of a register
> read or write.
> It is not possible to use the CS line as a GPIO on some SoC, so we
> need to workaround this by implementing a single SPI transfer to
> access the PMIC.

Reviwed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

though it's really sad this can't be done in the SPI controller where
the bug is.  You should also set use_single_rw in the regmap_config,
though this is less critical as currently the core won't automatically
generate any bulk I/O.

Obviously this will affect a much wider range of devices when used with
i.MX.
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