When atmel_pwm_config() calculates and then sets the prescaler, it is
overwriting the channel's CMR register so we are losing the CPOL
configuration.

As atmel_pwm_config() is always called before enabling a channel,
inverting the polarity doesn't work.

Fix that by reading CMR first and only overwriting the prescaler bits.
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: NNicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: NThierry Reding <thierry.reding@gmail.com>

When the PWM controller is registered successfully, the clock can not
unprepare, so fix it.
Signed-off-by: NBo Shen <voice.shen@atmel.com>
Signed-off-by: NThierry Reding <thierry.reding@gmail.com>

Add a PWM framework driver for the PWM controller found on Atmel SoCs.
Signed-off-by: NBo Shen <voice.shen@atmel.com>
Acked-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: NJean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
[thierry.reding: coding style and other minor cleanups]
Signed-off-by: NThierry Reding <thierry.reding@gmail.com>